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Ca. Accumulibacter was the predominant microorganism (relative FISH bio-abundance of 67 ± 5%) in a lab-scale sequential batch reactor that accomplished enhanced biological phosphorus removal (EBPR) while using glucose and acetate as the carbon sources (1:1 COD-based ratio). Both organic compounds were completely anaerobically consumed. The reactor's performance in terms of P/C ratio, phosphorous release and uptake, and overall kinetic and stoichiometric parameters were on the high end of the reported spectrum for EBPR systems (100:9.3 net mg phosphate removal per mg COD consumed when using glucose and acetate in a 1:1 ratio). The batch tests showed that, to the best of our knowledge, this is the first time a reactor enriched with Ca. Accumulibacter can putatively utilize glucose as the sole carbon source to biologically remove phosphate (COD:P (mg/mg) removal ratio of 100:6.3 when using only glucose). Thus, this research proposes that Ca. Accumulibacter directly anaerobically stored the fed glucose primarily as glycogen by utilizing the ATP provided via the hydrolysis of poly-P and secondarily as PHA by balancing its ATP utilization (glycogen generation) and formation (PHA storage). Alternative hypotheses are also discussed. The reported findings could challenge the conventional theories of glucose assimilation by Ca. Accumulibacter, and can be of significance for the biological removal of phosphorus from wastewaters with high contents of fermentable compounds or low VFAs.

Various business models for fecal sludge emptying and transport have been developed to address challenges and their advantages have been documented; however, their evaluation has not been investigated. This study developed an evaluation framework, which was tested in informal settlements in Kampala for sustainable business models of fecal sludge emptying and transport. Through key informant interviews and stakeholder consultations, service delivery challenges from informal settlements in Kampala were identified and included in the framework, which were: high cost of emptying services, spillages, access to facilities, high operational costs and social stigma. The evaluation framework adopted six service criteria: Financial, Institutional, Environmental, Technological, Social and Scalability; these were further defined by fifteen service sub-criteria. The criteria were tested separately on eight business models—for mechanized (cesspool) and semi-mechanized (gulper) technologies. The key output of the evaluation framework (business model scorecard) revealed that two models (scheduled desludging and call center) for cesspool technology and three models (mobile transfer stations, scheduled desludging and call center) for gulper technology have high potential for service improvement in informal settlements. Scheduled desludging and mobile transfer stations can effectively optimize emptying services and subsequently reduce emptying charges, whereas the call center is critical for bridging service delivery.

Thermal drying is an effective sludge treatment method for dealing with large volumes of sludge. Microwave (MW) technology has been proposed as an effective and efficient technology for sludge drying. The physical-chemical properties of the sludge depend both on the origin of the sludge, as well as on the treatment process at which the sludge has been exposed. The physical-chemical properties of the sludge affect the performance and the subsequent valorisation and management of the sludge. This study evaluated the effect of certain physical-chemical properties of the sludge (moisture content, organic content, calorific value, porosity, hydrophobicity, and water-sludge molecular interaction, among others) on the MW sludge drying and energy performance. Four different types of sludge were evaluated collected from municipal wastewater treatment plants and septic tanks. The performance of the MW system was assessed by evaluating the sludge drying rates, exposure times, energy efficiencies and power input consumed by the MW system and linking the MW drying performance to the sludge physical-chemical properties. The results confirmed that MW drying substantially extends the constant drying period associated with unbound water evaporation, irrespective of the sludge sample evaluated. However, the duration and intensity were determined to depend on the dielectric properties of the sludge, particularly on the distribution of bound and free water. Sludge samples with a higher amount of free and loosely bound water absorbed and converted MW energy into heat more efficiently than sludge samples with a lower amount of free water. As a result, the sludge drying rates increased and the constant drying rate period prolonged; hence, leading to an increase in MW drying energy efficiency. The availability of free and loosely bound water molecules was favoured when hydrophobic compounds, e.g., oils and fats, were present in the sludge.

Although faecal sludge (FS) co-compost contains vital nutrients, there are several barriers limiting adoption and reuse of FS co-compost in agriculture. This study in Bhubaneswar found that health risk and bad odour were the two topmost negative perceptions of FS co-compost reuse. The main factors influencing farmers’ negative perceptions of FS co-compost were bad odour and fear of infection, whereas socio-cultural/religious beliefs and bad odour were the key factors influencing the negative perceptions of urban households practising kitchen gardening (UHPKG). Fear of infection and bad odour were the key factors influencing fertiliser retailers’ negative perceptions, while inadequate information, unavailability, and lack of government policy on FS co-compost reuse were the key factors influencing Farmer Producer Organisations’ negative perceptions. The majority of farmers (95%) and UHPKG (72%) were unwilling to consume food crops grown with FS co-compost, mainly because of feelings of disgust, fear of infection, and religious and socio-cultural beliefs.

The aerobic granular sludge (AGS) process is an effective wastewater treatment technology for organic matter and nutrient removal that has been introduced in the market rapidly. Until now, limited information is available on AGS regarding the removal of bacterial and viral pathogenic organisms present in sewage. This study focussed on determining the relation between reactor operational conditions (plug flow feeding, turbulent aeration and settling) and physical and biological mechanisms on removing two faecal surrogates, Escherichia coli and MS2 bacteriophages. Two AGS laboratory-scale systems were separately fed with influent spiked with 1.0 × 106 CFU/100 mL of E. coli and 1.3 × 108 PFU/100 mL of MS2 bacteriophages and followed during the different operational phases. The reactors contained only granular sludge and no flocculent sludge. Both systems showed reductions in the liquid phase of 0.3 Log10 during anaerobic feeding caused by a dilution factor and attachment of the organisms on the granules. Higher removal efficiencies were achieved during aeration, approximately 1 Log10 for E. coli and 0.6 Log10 for the MS2 bacteriophages caused mainly by predation. The 18S sequencing analysis revealed high operational taxonomic units (OTUs) of free-living protozoa genera Rhogostoma and Telotrochidium concerning the whole eukaryotic community. Attached ciliates propagated after the addition of the E. coli, an active contribution of the genera Epistylis, Vorticella, and Pseudovorticella was found when the reactor reached stability. In contrast, no significant growth of predators occurred when spiking the system with MS2 bacteriophages, indicating a low contribution of protozoa on the phage removal. Settling did not contribute to the removal of the studied bacterial and viral surrogates. M.L. Barrios-Hernández acknowledges the Technological Institute of Costa Rica for providing the fellowship (Grant Number 007-2014-M) to pursue her PhD programme (2016-2020) at IHE-Delft, the Netherlands. K. Mora-Cabrera acknowledges the Generalitat Valenciana (GRISOLIAP/2017/173) and the European Social Funds (BEFPI/2019/065) for their financial support.

The provision of effective sanitation strategies has a significant impact on public health. However, the treatment of septic sludge still presents some challenges worldwide. Consequently, innovative technologies capable of an effective and efficient sludge treatment, mostly at a decentralized level, are in high demand to improve sanitation provision. To address this problem, this study evaluates a novel semi-decentralised mobile faecal sludge treatment system, the pilot-system for which consists of a combination of several individual processes including mechanical dewatering (MD), microwave (MW) drying, and membrane filtration (ultrafiltration [UF] and reverse osmosis [RO]). The system evaluation was carried out by treating raw, partially digested faecal sludge (FS) from septic tanks—hence, septic sludge (SS)—in the Jordan Valley, Jordan. The pilot-scale system exhibited an effective and flexible treatment performance for (i) sanitizing faecal sludge and related liquid streams (MW and UF); (ii) reducing the treated sludge mass (and sludge volume) (MD and MW); and (iii) producing a high-quality treated liquid stream ideal for water reclamation applications (UF and RO). The MD process removed approximately 99% of the initial SS water content. The MW drying system completely removed E. coli and dehydrated the dewatered sludge at low energy expenditures of 0.75 MJ kg−1 and 5.5 MJ kg−1, respectively. Such energy expenditures can be further reduced by approximately 40% by recovering energy in the condensate and burning the dried sludge, which can then be reused inland applications. The membrane filtration system (UF and RO) was able to produce high-quality treated water that is ideal for the water reuse applications that irrigation requires, as well as meeting the Jordanian standard 893/2006. In addition, the system can also be powered by renewable energy sources, such as photovoltaic energy. Therefore, this research demonstrates that the evaluated semi-decentralised mobile system is technically feasible for the in situ treatment of SS (sanitization and dehydration), while also being effective for simultaneously recovering valuable resources, such as energy, water, and nutrients.

In this study, the impact of applied solids retention time (SRT) on the biological performance of an anaerobic membrane bioreactor (AnMBR) treating synthetic dairy wastewater with high lipid content was assessed. Two side-stream AnMBR systems were operated at an SRT of 20 and 40 days (R20 and R40, respectively), equipped with an inside-out tubular membrane operated in cross-flow mode under full-scale operational conditions, i.e. crossflow velocity, transmembrane pressure, membrane flux. Successful operation was achieved and removal efficiencies of both reactors were up to 99% applying an organic loading rate (OLR) of 4.7 g COD L−1 d−1. No precipitation of lipids was observed throughout the operational period, keeping the lipids available for the anaerobic degradation. Long chain fatty acid (LCFA) accumulation was very modest and amounted 148 and 115 mg LCFA-COD per gram of volatile suspended solids (VSS) for R20 and R40, respectively. At an SRT of 40 days, a slightly better biological conversion was obtained. Periodically performed specific methanogenic activity (SMA) tests showed stabilization of the SMA for R40 sludge, whereas for R20 sludge the SMA continued to decrease. This study revealed a more stable reactor performance operating the AnMBR at an SRT of 40 days compared to 20 days.

A majority of the world's population use onsite sanitation systems, which store or treat excreta close to where it is generated. Sludge from these systems needs to be managed through a series of stages, known as the sanitation value chain. There is a huge diversity of service providers, not only within each part of the chain, but also along the chain bridging the different components. These service providers are linked not only by the flow of materials, but also by the transfer of money. Therefore for this system to be considered financially sustainable all services from the toilet to reuse or disposal need to be considered. A tool has been developed (eSOSView™) to simulate, evaluate, and optimise the financial flows along and within the sanitation value chain. In this paper eSOSView™ was tested, validated (using existing data), and piloted (including data collection). This paper demonstrates how eSOSView ™ can be used to evaluate different financial flow models, to assess financial sustainability in different parts of the sanitation value chain and optimise the financial sustainability along the sanitation value chain.

In Khulna, Bangladesh, mechanical faecal sludge (FS) emptying and transport (E&amp, T) service is provided by community development committees (CDCs) and the Khulna City Corporation (KCC). Without considering capital expenditure and depreciation, financial analysis for one year revealed that a CDC-1 m3 vacutug made a profit of Bangladeshi taka (BDT) 145,780 (USD $1746) whereas a KCC-2 m3 vacutug was in the loss of BDT 218,179 (USD $2613). There is a need to engage the private sector for sustainable service provision. Some of the key elements of enabling the environment for private sector engagement are policy/strategy, institutional and regulatory framework, implementation capacity, and financial viability. Existing policy/strategy/frameworks acknowledged the need and suggested plans for private sector engagement, and decentralised authority to city corporations. With increasing private–public partnership projects and collaboration in the sanitation sector, capacity of the KCC and the private sector are increasing. Financial viability of the FS E&amp, T business is primarily dependent on the number of trips and the emptying fee. For the E&amp, T business to be financially viable, a 2 m3 vacutug should make six trips/day (internal rate of return (IRR)—13%, discount rate—6.5%) with an emptying fee of BDT 750 (USD $9)/m3. Despite the lack of operative guidelines for faecal sludge management (FSM), enabling the environment for private sector engagement in FS E&amp, T business in Khulna seems favourable.

Photo-activated sludge (PAS) systems are an emerging wastewater treatment technology where microalgae provide oxygen to bacteria without the need for external aeration. There is limited knowledge on the optimal conditions for enhanced biological phosphorus removal (EBPR) in systems containing a mixture of polyphosphate accumulating organisms (PAOs) and microalgae. This research aimed to study the effects of substrate composition and light intensity on the performance of a laboratory-scale EBPR-PAS system. Initially, a model-based design was developed to study the effect of organic carbon (COD), inorganic carbon (HCO3) and ammonium-nitrogen (NH4-N) in nitrification deprived conditions on phosphorus (P) removal. Based on the mathematical model, two different synthetic wastewater compositions (COD:HCO3:NH4-N: 10:20:1 and 10:10:4) were examined at a light intensity of 350 µmol m−2 sec−1. Add to this, the performance of the system was also investigated at light intensities: 87.5, 175, and 262.5 µmol m−2 sec−1 for short terms. Results showed that wastewater having a high level of HCO3 and low level of NH4-N (ratio of 10:20:1) favored only microalgal growth, and had poor P removal due to a shortage of NH4-N for PAOs growth. However, lowering the HCO3 level and increasing the NH4-N level (ratio of 10:10:4) balanced PAOs and microalgae symbiosis, and had a positive influence on P removal. Under this mode of operation, the system was able to operate without external aeration and achieved a net P removal of 10.33 ±1.45 mg L−1 at an influent COD of 100 mg L−1. No significant variation was observed in the reactor performance for different light intensities, indicating the EBPR-PAS system can be operated at low light intensities with a positive influence on P removal.

The implementation of near-infrared (NIR) spectroscopy in the wastewater treatment has been continuously expanding. As an alternative to the conventional analytical methods for monitoring constituents in wastewater treatment processes, the use of NIR spectroscopy is considered cost-effective and less time- consuming. NIR spectroscopy does not in any way adulterate measured sample as no prior treatment is needed thus making it a waste-free technique. On the negative side, one must be very well acquainted with chemometric techniques to interpret results. In this study, filtered and centrifuged wastewater and sludge samples obtained from a lab-scale membrane bioreactor (MBR) were analysed. Essential wastewater constituents were determined and compared, employing two analytical methods (conventional and NIR spectroscopy). Special attention was given to the soluble microbial products (SMP) and the extracellular polymeric substances (EPS) which are known to promote membrane fouling. The measured parameters through NIR spectroscopy were analysed and processed by partial least squares regression (PLSR) and artificial neural networks (ANN) models to assess whether the evaluated wastewater constituents could be monitored by NIR spectroscopy. Very good results were obtained with PLSR models except for the determination of SMP thus limiting the model for their monitoring to qualitative rather than quantitative. ANN exhibited a better performance in terms of correlating NIR spectra with all the measured parameters, resulting in correlation coefficients in most cases higher than 0.97 for training, test, and validation. Based on the results achieved by this research, the combination of NIR spectra and chemometric modelling offers advantages compared to conventional analytical methods.

Conventional diffused aeration systems (such as fine-bubble diffusers) exhibit a poor oxygen transfer in wastewater treatment plants (WWTPs), particularly when operating at sludge concentrations higher than 15 g L−1. The supersaturated dissolved oxygen (SDOX) system has been proposed as an alternative for supplying dissolved oxygen (DO) at high mixed liquor suspended solids (MLSS) concentrations. The advantages introduced by such technology include the possibility of operating WWTPs at much higher than usual MLSS concentrations, increasing the treatment capacity of WWTPs. Recent studies have demonstrated that the SDOX system has higher oxygen transfer rates (OTRs) and oxygen transfer efficiencies (OTEs) relative to fine-bubble diffusers. However, it is unknown if the high-pressure conditions introduced by SDOX may possibly impact the biological performance of WWTPs. In this study, the effects of SDOX technology on the biological performance of a membrane bioreactor (MBR) were evaluated. The MBR was operated at an MLSS concentration of approximately 15 g L−1 in four phases as follows: (P1) with bubble diffusers, (P2) with an SDOX unit, (P3) with the bubble diffusers, and (P4) with the SDOX unit. The performance of the MBR was assessed by monitoring the sludge concentration, as well as changes in the particle size distribution (PSD), sludge activity, organic matter removal and nitrification performance, and changes in the microbial community within the MBR. The operational conditions exerted by the SDOX technology did not affect the concentration of active biomass during the study period. The biological performance of the MBR was not affected by the introduction of the SDOX technology. Finally, the microbial community was relatively stable although some variations at the family and genus level were evident during each of the study phases. Therefore, the SDOX system can be proposed as an alternative technology for DO supply in WWTPs increasing the overall treatment capacity.

In the last decade, flooding has caused the death of over 60,000 people and affected over 900 million people globally. This is expected to increase as a result of climate change, increased populations and urbanisation. Floods can cause infections due to the release of water-borne pathogenic microorganisms from surcharged combined sewers and other sources of fecal contamination. This research contributes to a better understanding of how the occurrence of water-borne pathogens in contaminated shallow water bodies is affected by different environmental conditions. The inactivation of fecal indicator bacteria Escherichia coli was studied in an open stirred reactor, under controlled exposure to simulated sunlight, mimicking the effect of different latitudes and seasons, and different concentrations of total suspended solids (TSS) corresponding to different levels of dilution and runoff. While attachment of bacteria on the solid particles did not take place, the decay rate coefficient, k (d−1), was found to depend on light intensity, I (W m−2), and duration of exposure to sunlight, T (h d−1), in a linear way (k = kD+ 0.03·I and k = kD+ 0.65·T, respectively) and on the concentration of TSS (mg L−1), in an inversely proportional exponential way (k = kD+ 14.57·e−0.02·[TSS]). The first-order inactivation rate coefficient in dark conditions, kD= 0.37 d−1, represents the effect of stresses other than light. This study suggests that given the sunlight conditions during an urban flood, and the concentration of indicator organisms and TSS, the above equations can give an estimate of the fate of selected pathogens, allowing rapid implementation of appropriate measures to mitigate public health risks. Electronic supplementary material The online version of this article (10.1007/s41742-018-0160-5) contains supplementary material, which is available to authorized users., Article Highlights It was demonstrated under controlled conditions that the inactivation of fecal indicator bacteria E. coli is higher under higher solar irradiance, longer duration of daylight and low TSS concentrations.The results indicate that under high TSS concentrations the bacteria, even if not attached on particles, are protected from photo-inactivation for a period of a few days, as the decay rate decreases exponentially with an increase in TSS concentration. Electronic supplementary material The online version of this article (10.1007/s41742-018-0160-5) contains supplementary material, which is available to authorized users.

An eSOS (emergency Sanitation Operation System) Smart Toilet experimental prototype, aimed at improving the provision of safe sanitation in emergency settings, was field tested in a temporary settlement in Tacloban City, Philippines. The design, usage, and user acceptance of the toilet were all evaluated. Quantitative and qualitative data were collected through interviews and questionnaires, supported by the research-team's observations. The survey results indicated that 98% of users (both first-time users and those who tried it a few times) intended to use the toilet again. There were more features that the users liked than disliked. The in-built water supply and user-operated smart toilet features were liked, but the bad smell was disliked. User-operated smart features were an important factor in user acceptance although they were not the main incentives. Key recommendations are to improve the toilet's design to address the odor and cleanliness issues, make handwashing more convenient, and lower the height of the toilet bowl.

Sulfate rich wastewaters can be generated from industry, use of seawater in urban environments, or by saline water infiltration into the sewerage. Under anaerobic conditions sulfate can be converted to sulfide, which may affect micro-organisms performing biological nutrient removal. The objective of this study was to evaluate the effect of sulfide on the activity of polyphosphate-accumulating organisms (PAO) in the anaerobic stage of the enhanced biological phosphorus removal process (EBPR). In this regard, a highly enriched culture of PAO was exposed in short-term activity tests to a range of sulfide concentrations at different operational pH values. The PAO activity was mainly affected by un-dissociated H2S. The specific acetate uptake rate was inhibited by 50% at around 60 mg H2S.L−1. With increasing H2S concentrations, higher phosphate release rate to acetate uptake rate ratios were observed, possibly due to increased energy requirements for cell detoxification. Mathematical expressions were developed, which satisfactorily described the sulfide effects on the acetate uptake rate and phosphate release rate. The results show that, dependent on the pH, EBPR might be negatively affected by total sulfide concentrations exceeding 275 mg SO4.L−1 at pH 6.5 or 1200 mg SO4.L−1 at pH 7.8 mg SO4.L−1 or when freshwater is partially replaced by seawater more than 45% (pH 7.8) or 10% (pH 6.5) used as secondary quality water. The findings of this study imply that sulfide, which is commonly found in different type of wastewaters, affects the anaerobic metabolism of PAO and may play an important role in the process performance of treatment plants treating wastewaters with high sulfide content.

Eutrophication episodes have been recently observed in the Santa Lucia river basin (SLRB) in Uruguay, the main drinking water source for approximately 60% of the Uruguayan population. The local environmental authorities have been strengthening the discharge standards for that particular river basin. There are several industries currently discharging their wastewater directly into the SLRB; some of these industries are required to upgrade their current wastewater treatment systems to comply with the new regulations. This study evaluated the performance of a membrane bioreactor (MBR) on dairy wastewater as a potential treatment technology for fulfilling the new discharge standards. A pilot MBR was placed at the dairy industry wastewater treatment system at two different locations: (i) receiving the wastewater from the industrial process after passing through a grease removal pond (high load stream); and (ii) receiving the wastewater after passing through the grease removal pond and an anaerobic pond (low load stream). The pilot MBR was operated at the following conditions for approximately four months: total sludge retention, hydraulic retention time (HRT) of 25 h, an average influent flow rate of 1.3 m3 day−1, and at two different average chemical oxygen demand (COD) influent concentrations: 1300 mg L−1 (high load stream) and 385 mg L−1 (low load stream). The average reported removal efficiencies on COD, biological oxygen demand (BOD), and ammonium (NH4-N) were 94.1, 98.1, and 99.6%, respectively. In addition, it was observed that for a COD/N ratio above 10, total nitrogen (TN) and total phosphorous (TP) were well removed with average removal efficiencies of 93.1 and 91.0%, respectively. The MBR effluent met the new Uruguayan standards for discharging into the SLRB, and it can be further considered for water reuse at the industrial process. Moreover, a financial feasibility study was carried out for the implementation of a full scale MBR at the existing dairy facility. The results of the feasibility study suggested to accept the investment for the implementation of the MBR technology at the dairy industry. The results of the feasibility analysis considered the high impact of penalties and fines imposed by the local government to the industry when not complying with the effluent discharge standards, as well as the critical situation regarding eutrophication of the SLRB while being the most important source for drinking water in Uruguay.

Reducing the footprint requirements of membrane bioreactors (MBR)s can both decrease the surface area needs for new wastewater treatment plants (WWTP)s, and increase the treatment capacities of existing WWTPs at a given surface area. In addition, it may promote the development of movable/portable containerized MBRs for a diverse range of wastewater treatment applications. Applications may include the provision of municipal/industrial wastewater treatment in remote areas without sewerage, and the provision of sanitation services under challenging site-specific conditions such as after the occurrence of a human-made or a natural disaster. The reduction of the footprint requirements of MBRs is constrained by the maximum amount of biomass that can be accommodated in the aerobic basin. The biomass concentration is mainly limited by the extremely low oxygen transfer efficiency (OTE) experienced by conventional aeration bubble diffuser systems at mixed liquor total suspended solids (MLSS) concentrations higher than 20 g L−1. Another potential limitation for the operation of MBRs at such high MLSS concentrations is the reduction on the membrane permeability due to excessive fouling. A pilot MBR with a treatment capacity of one m3 d−1 was installed at the research hall facilities at the Harnaschpolder wastewater treatment plant in Delft, The Netherlands. The MBR was operated at MLSS concentrations of up to 28 g L−1 at sludge retention times (SRT)s ranging from 30 to 35 days. The MBR was provided with a Speece cone concentrated oxygen delivery system to overcome the oxygen transfer limitations of conventional bubble diffuser aeration systems at high MLSS concentrations. The MBR performance was evaluated by monitoring the influent and effluent water quality, the membrane permeability, the sludge filterability, the dissolved oxygen (DO) concentration, and the oxygen uptake rate (OUR). The Speece cone proved to be effective in delivering enough oxygen to maintain DO concentrations in the MBR of approximately 2 mg L−1 at MLSS concentrations of up to 22 g L−1. OUR values above 200 mg L−1 h−1 were observed at 14 g L−1 MLSS and higher than 300 mg L−1 h−1 at 22 g L−1 MLSS. The MBR exhibited chemical oxygen demand (COD) removal efficiencies of up to 99% even at a hydraulic retention time (HRT) as low as 3.7 h. A reduction in permeability from 33 to 11 lmh bar−1 was observed when the MLSS concentrations increased from 18.7 to 27.8 g L−1. Sludge filterability values expressed as the added resistance (ΔR20) fell in the range of “poor filterability” for all the evaluated operational conditions; however, a lower filtration resistance in the range of “moderate filterability” at approximately 23 g L−1 MLSS was noticed. The experimental results suggest that at the evaluated experimental conditions the existent limitations on poor oxygen transfer and low permeability when operating a MBR at high MLSS concentrations can be overcome; therefore, the footprint requirements of MBR systems may be further reduced.

The co-treatment of two synthetic faecal sludges (FS-1 and FS-2) with municipal synthetic wastewater (WW) was evaluated in an aerobic granular sludge (AGS) reactor. After characterisation, FS-1 showed the following concentrations, representative for medium-strength FS: 12,180 mg TSS L−1, 24,300 mg total COD L−1, 93.8 mg PO3-P L−1, and 325 mg NH4-N L−1. The NO3-N concentration was relatively high (300 mg L−1). For FS-2, the main difference with FS-1 was a lower nitrate concentration (18 mg L−1). The recipes were added consecutively, together with the WW, to an AGS reactor. In the case of FS-1, the system was fed with 7.2 kg total COD m−3d−1 and 0.5 kg Nitrogen m−3d−1. Undesired denitrification occurred during feeding and settling resulting in floating sludge and wash-out. In the case of FS-2, the system was fed with 8.0 kg total COD m−3d−1 and 0.3 kg Nitrogen m−3d−1. The lower NO3-N concentration in FS-2 resulted in less floating sludge, a more stabilised granular bed and better effluent concentrations. To enhance the hydrolysis of the slowly biodegradable particulates from the synthetic FS, an anaerobic stand-by period was added and the aeration period was increased. Overall, when compared to a control AGS reactor, a lower COD consumption (from 87 to 35 mg g−1 VSS h−1), P-uptake rates (from 6.0 to 2.0 mg P g VSS−1 h−1) and NH4-N removal (from 2.5 to 1.4 mg NH4-N g VSS−1 h−1) were registered after introducing the synthetic FS. Approximately 40% of the granular bed became flocculent at the end of the study, and a reduction of the granular size accompanied by higher solids accumulation in the reactor was observed. A considerable protozoa Vorticella spp. bloom attached to the granules and the accumulated particles occurred; potentially contributing to the removal of the suspended solids which were part of the FS recipe.

Sewage sludge management and treatment can represent up to approximately 30% of the overall operational costs of a wastewater treatment plant. Microwave (MW) drying has been recognized as a feasible technology for sludge treatment. However, MW drying systems exhibit high energy expenditures due to: (i) unnecessary heating of the cavity and other components of the system, (ii) ineffective extraction of the condensate from the irradiation cavity, and (iii) an inefficient use of the microwave energy, among others issues. This study investigated the performance of a novel pilot-scale MW system for sludge drying, specifically designed addressing the shortcomings previously described. The performance of the system was assessed drying municipal centrifuged wasted activated sludge at MW output powers from 1 to 6 kW and evaluating the system's drying rates and exposure times, specific energy outputs, MW generation efficiencies, overall energy efficiencies, and specific energy consumption. The results indicated that MW drying significantly extends the duration of the constant rate drying period associated with the evaporation of the unbound sludge water, a phase associated with low energy input requirement for evaporating water. Moreover, the higher the MW output power, the higher the sludge power absorption density, and the MW generation efficiency. MW generation efficiencies of up to 70% were reported. The higher the power absorption density, the lower the chances for energy losses in the form of reflected power and/or energy dissipated into the MW system. Specific energy consumptions as low as 2.6 MJ L−1 (0.74 kWh L−1) could be achieved, well in the range of conventional thermal dryers. The results obtained in this research provide sufficient evidence to conclude that the modifications introduced to the novel pilot-scale MW system mitigated the shortcomings of existing MW systems, and that the technology has great potential to effectively and efficiently drying municipal sewage sludge.

Populations of “Candidatus Accumulibacter”, a known polyphosphate-accumulating organism, within clade IC have been proposed to perform anoxic P-uptake activity in enhanced biological phosphorus removal (EBPR) systems using nitrate as electron acceptor. However, no consensus has been reached on the ability of “Ca. Accumulibacter” members of clade IC to reduce nitrate to nitrite. Discrepancies might relate to the diverse operational conditions which could trigger the expression of the Nap and/or Nar enzyme and/or to the accuracy in clade classification. This study aimed to assess whether and how certain operational conditions could lead to the enrichment and enhance the denitrification capacity of “Ca. Accumulibacter” within clade IC. To study the potential induction of the denitrifying enzyme, an EBPR culture was enriched under anaerobic–anoxic–oxic (A2O) conditions that, based on fluorescence in situ hybridization and ppk gene sequencing, was composed of around 97% (on a biovolume basis) of affiliates of “Ca. Accumulibacter” clade IC. The influence of the medium composition, sludge retention time (SRT), polyphosphate content of the biomass (poly-P), nitrate dosing approach, and minimal aerobic SRT on potential nitrate reduction were studied. Despite the different studied conditions applied, only a negligible anoxic P-uptake rate was observed, equivalent to maximum 13% of the aerobic P-uptake rate. An increase in the anoxic SRT at the expenses of the aerobic SRT resulted in deterioration of P-removal with limited aerobic P-uptake and insufficient acetate uptake in the anaerobic phase. A near-complete genome (completeness = 100%, contamination = 0.187%) was extracted from the metagenome of the EBPR biomass for the here-proposed “Ca. Accumulibacter delftensis” clade IC. According to full-genome-based phylogenetic analysis, this lineage was distant from the canonical “Ca. Accumulibacter phosphatis”, with closest neighbor “Ca. Accumulibacter sp. UW-LDO-IC” within clade IC. This was cross-validated with taxonomic classification of the ppk1 gene sequences. The genome-centric metagenomic analysis highlighted the presence of genes for assimilatory nitrate reductase (nas) and periplasmic nitrate reductase (nap) but no gene for respiratory nitrate reductases (nar). This suggests that “Ca. Accumulibacter delftensis” clade IC was not capable to generate the required energy (ATP) from nitrate under strict anaerobic-anoxic conditions to support an anoxic EBPR metabolism. Definitely, this study stresses the incongruence in denitrification abilities of “Ca. Accumulibacter” clades and reflects the true intra-clade diversity, which requires a thorough investigation within this lineage.

The high frequency and intensity of urban floods caused by climate change, urbanisation and infrastructure failures increase public health risks when the flood water contaminated from combined sewer overflows (CSOs) or other sources of faecal contamination remains on urban surfaces. This study contributes to a better understanding of the effects of urban and recreational surfaces on the occurrence of waterborne pathogens. The inactivation of selected indicator organisms was studied under controlled exposure to artificial sunlight for 6 h followed by 18 h in dark conditions. Concrete, asphalt, pavement blocks and glass as control were inoculated with artificial floodwater containing, as indicator organisms, Escherichia coli bacteria, which are common faecal indicator bacteria (FIB) for water quality assessment, Bacillus subtilis spores chosen as surrogates for Cryptosporidium parvum oocysts and Giardia cysts, and bacteriophages MS2 as indicators for viral contamination. On practically all the surfaces in this study, E. coli had the highest inactivation under light conditions followed by MS2 and B. subtilis, except asphalt where MS2 was inactivated faster. The highest inactivation under light conditions was seen with E. coli on a concrete surface (pH 9.6) with an inactivation rate of 1.85 h−1. However, the pH of the surfaces (varying between 7.0 and 9.6) did not have any influence on inactivation rates under dark conditions. MS2 bacteriophage had the highest inactivation under light conditions on asphalt with a rate of 1.29 h−1. No die-off of B. subtilis spores was observed on any of the surfaces during the experiment, neither in light nor in dark conditions. This study underpins the need to use different indicator organisms to test their inactivation after flooding. It also suggests that given the sunlight conditions, concentration of indicator organisms and type of surface, the fate of waterborne pathogens after a flood could be estimated.

Sulphate-rich wastewaters can be generated due to (i) use of saline water as secondary-quality water for sanitation in urban environments (e.g. toilet flushing), (ii) discharge of industrial effluents, (iii) sea and brackish water infiltration into the sewage and (iv) use of chemicals, which contain sulphate, in drinking water production. In the presence of an electron donor and absence of oxygen or nitrate, sulphate can be reduced to sulphide. Sulphide can inhibit microbial processes in biological wastewater treatment systems. The objective of the present study was to assess the effects of sulphide concentration on the anaerobic and aerobic physiology of polyphosphate-accumulating organisms (PAOs). For this purpose, a PAO culture, dominated by Candidatus Accumulibacter phosphatis clade I (PAO I), was enriched in a sequencing batch reactor (SBR) fed with acetate and propionate. To assess the direct inhibition effects and their reversibility, a series of batch activity tests were conducted during and after the exposure of a PAO I culture to different sulphide concentrations. Sulphide affected each physiological process of PAO I in a different manner. At 189 mg TS-S/L, volatile fatty acid uptake was 55% slower and the phosphate release due to anaerobic maintenance increased from 8 to 18 mg PO4-P/g VSS/h. Up to 8 mg H2S-S/L, the decrease in aerobic phosphorus uptake rate was reversible (Ic60). At higher concentrations of sulphide, potassium (>16 mg H2S-S/L) and phosphate (>36 mg H2S-S/L) were released under aerobic conditions. Ammonia uptake, an indicator of microbial growth, was not observed at any sulphide concentration. This study provides new insights into the potential failure of enhanced biological phosphorus removal sewage plants receiving sulphate- or sulphide-rich wastewaters when sulphide concentrations exceed 8 mg H2S-S/L, as PAO I could be potentially inhibited.

A laboratory-scale microwave (MW) unit was applied to treat fresh blackwater sludge that represented fecal sludge (FS) produced at heavily used toilet facilities. The sludge was exposed to MW irradiation at different power levels and for various durations. Variables such as sludge volume and pathogen reduction were observed. The results demonstrated that the MW is a rapid and efficient technology that can reduce the sludge volume by over 70% in these experimental conditions. The concentration of bacterial pathogenic indicator E. coli also decreased to below the analytical detection levels. Furthermore, the results indicated that the MW operational conditions including radiation power and contact time can be varied to achieve the desired sludge volume and pathogen reduction. MW technology can be further explored for the potential scaling-up as an option for rapid treatment of FS from intensively used sanitation facilities such as in emergency situations., Graphical abstract, Highlights • There is lack of fast and efficient fecal sludge treatment options in emergencies. • Microwave treatment is rapid and efficient in sludge volume and pathogen reduction. • Power and contact time can be varied to reach diverse levels of sludge treatment.

Sanitation infrastructure are not able to cope with the increasing population in low-income countries, which leaves populations exposed to faecal contamination from multiple pathways. This study evaluated public health risk (using SaniPath) in a low-income community during the dry season, to identify the dominant exposure pathways, and compare this data to existing data for the rainy season, questioning the assumption that risk of faecal contamination is higher in the rainy season. SaniPath was used to collect and assess exposure and environmental data, and to generate risk profiles for each pathway. In the dry season the highest exposure frequency was for bathing and street food, exposure frequency generally increased, and seasonal variation was found in five pathways. The highest hazards in the dry season were through contact with drains, soil, and street food. Seasonal variation was found in the contamination of open drains and street food, with higher levels of Escherichia coli (E. coli) in the dry season. Open drains were identified as the most dominant risk pathway in both seasons, but risk was higher in the dry season. This highlights the complex nature of seasonal variation of faecal risk, and questions the assumption that risk is higher in the rainy season.

Candidatus Accumulibacter phosphatis is in general presented as the dominant organism responsible for the biological removal of phosphorus in activated sludge wastewater treatment plants. Lab-scale enhanced biological phosphorus removal (EBPR) studies, usually use acetate as carbon source. However, the complexity of the carbon sources present in wastewater could allow other potential poly-phosphate accumulating organism (PAOs), such as putative fermentative PAOs (e.g., Tetrasphaera), to proliferate in coexistence or competition with Ca. Accumulibacter. This research assessed the effects of lactate on microbial selection and process performance of an EBPR lab-scale study. The addition of lactate resulted in the coexistence of Ca. Accumulibacter and Tetrasphaera in a single EBPR reactor. An increase in anaerobic glycogen consumption from 1.17 to 2.96 C-mol/L and anaerobic PHV formation from 0.44 to 0.87 PHV/PHA C-mol/C-mol corresponded to the increase in the influent lactate concentration. The dominant metabolism shifted from a polyphosphate-accumulating metabolism (PAM) to a glycogen accumulating metabolism (GAM) without EBPR activity. However, despite the GAM, traditional glycogen accumulating organisms (GAOs; Candidatus Competibacter phosphatis and Defluvicoccus) were not detected. Instead, the 16s RNA amplicon analysis showed that the genera Tetrasphaera was the dominant organism, while a quantification based on FISH-biovolume indicated that Ca. Accumulibacter remained the dominant organism, indicating certain discrepancies between these microbial analytical methods. Despite the discrepancies between these microbial analytical methods, neither Ca. Accumulibacter nor Tetrasphaera performed biological phosphorus removal by utilizing lactate as carbon source.

Emergency sanitation technologies make up some of the most significant gaps in the water, sanitation and hygiene sector. Major initiatives to address identified gaps may be characterised as donor-funded, top-down processes driven by international or European-based non-governmental organisations. However, local organisations also innovate. To better understand how local organisations innovate for emergency sanitation, the paper presents a case study of an Indonesian NGO who had developed a toilet for use in emergencies. The NGO developed the toilet by modifying an existing non-emergency toilet. The process was unstructured and informal. When testing ideas, for instance, the NGO used their own methods rather than referring to testing protocols recognised by the industry. The NGO surveyed end users, but the respondents did not come from post-disaster settings. Compared to designs developed through international initiatives, the NGO's design deviated somewhat from internationally recognised standards, for instance, the size of the latrine slab. The paper also discusses differences between the way local and international organisations develop emergency sanitation products. Each approach has advantages and disadvantages in terms of methodology and access to resources and expertise. Therefore, there are potential benefits to the different organisations working more closely.

In this research, three faecal sludge sanitizing methods—lactic acid fermentation, urea treatment and lime treatment—were studied for application in emergency situations. These methods were investigated by undertaking small scale field trials with pit latrine sludge in Blantyre, Malawi. Hydrated lime was able to reduce the E. coli count in the sludge to below the detectable limit within 1 h applying a pH &gt, 11 (using a dosage from 7% to 17% w/w, depending faecal sludge alkalinity), urea treatment required about 4 days using 2.5% wet weight urea addition, and lactic acid fermentation needed approximately 1 week after being dosed with 10% wet weight molasses (2 g (glucose/fructose)/kg) and 10% wet weight pre-culture (99.8% pasteurised whole milk and 0.02% fermented milk drink containing Lactobacillus casei Shirota). Based on Malawian prices, the cost of sanitizing 1 m3 of faecal sludge was estimated to be €32 for lactic acid fermentation, €20 for urea treatment and €12 for hydrated lime treatment.

Activated sludge systems have been applied for 100 years now. Over the course of the years, researchers have developed various models to describe activated sludge processes. The main aim has been to gain a better understanding of the conditions that favour the conversions of carbon, nitrogen and phosphorus present in wastewater, and associated oxygen consumption and sludge production. The current paper presents a reflection on the historical developments, state-of-the-art of activated sludge modelling and future trends. Over the years, many wastewater research groups have benefitted greatly from the development of activated sludge models (ASMs). On one hand, modelling has been expanded through the development of novel theoretical concepts and their application in new fields. On the other hand, models have been used for practical projects. Although, scientists are still searching for the ideal model, one can say that ASMs are developed to the extent that they can be applied in practice with confidence. New developments are expected to be seen regarding plant-wide modelling, integration with other models at the (urban) system level, organizational and computational infrastructure, and interface and communication with various stakeholders and users.

The concentration of sulphate present in wastewater can vary from 10 to 500 mg SO4 2−/L. During anaerobic conditions, sulphate is reduced to sulphide by sulphate-reducing bacteria (SRB). Sulphide generation is undesired in wastewater treatment plants (WWTPs). Previous research indicated that SRB are inhibited by the presence of electron acceptors (such as O2, NO3 and NO2). However, the contact times and concentrations used in those studies are by far higher than occur in WWTPs. Since sulphide can influence the biological nitrogen and phosphorus removal processes, this research aimed to understand how the different electron acceptors commonly present in biological nutrient removal (BNR) systems can affect the proliferation of SRB. For this purpose, a culture of SRB was enriched in a sequencing batch reactor (approx. 88% of the total bacteria population). Once enriched, the SRB were exposed for 2 h to typical concentrations of electron acceptors like those observed in BNR systems. Their activity was assessed using three different types of electron donors (acetate, propionate and lactate). Oxygen was the most inhibiting electron acceptor regardless the carbon source used. After exposure to oxygen and when feeding acetate, an inactivation time in the sulphate reduction activity was observed for 1.75 h. Once the sulphate reduction activity resumed, only 60% of the original activity was recovered. It is suggested that the proliferation of SRB is most likely to occur in BNR plants with an anaerobic fraction higher than 15% and operating at sludge retention times higher than 20 days (at a temperature of 20 °C). These results can be used to implement strategies to control the growth of sulphate reducers that might compete for organic carbon with phosphate-accumulating organisms. Electronic supplementary material The online version of this article (doi:10.1007/s00253-017-8340-3) contains supplementary material, which is available to authorized users.

The aim of this study was to evaluate the effectiveness of the novel aerobic granular sludge (AGS) wastewater treatment technology in removing faecal indicator organisms (FIOs) compared to the conventional activated sludge (CAS) treatment system. The work was carried out at two full-scale wastewater treatment plants (WWTP) in the Netherlands, Vroomshoop and Garmerwolde. Both treatment plants have a CAS and AGS system operated in parallel. The parallel treatment lines are provided with the same influent wastewater. The concentrations of the measured FIOs in the influent of the two WWTPs were comparable with reported literature values as follows: F-specific RNA bacteriophages at 106 PFU/100 mL, and Escherichia coli (E. coli), Enterococci, and Thermotolerant coliforms (TtC) at 105 to 106 CFU/100 mL. Although both systems (CAS and AGS) are different in terms of design, operation, and microbial community, both systems showed similar FIOs removal efficiency. At the Vroomshoop WWTP, Log10 removals for F-specific RNA bacteriophages of 1.4 ± 0.5 and 1.3 ± 0.6 were obtained for the AGS and CAS systems, while at the Garmerwolde WWTP, Log10 removals for F-specific RNA bacteriophages of 1.9 ± 0.7 and 2.1 ± 0.7 were found for the AGS and CAS systems. Correspondingly, E. coli, Enterococci, and TtC Log10 removals of 1.7 ± 0.7 and 1.1 ± 0.7 were achieved for the AGS and CAS systems at Vroomshoop WWTP. For Garmerwolde WWTP Log10 removals of 2.3 ± 0.8 and 1.9 ± 0.7 for the AGS and CAS systems were found, respectively. The measured difference in removal rates between the plants was not significant. Physicochemical water quality parameters, such as the concentrations of organic matter, nutrients, and total suspended solids (TSS) were also determined. Overall, it was not possible to establish a direct correlation between the physicochemical parameters and the removal of FIOs for any of the treatment systems (CAS and AGS). Only the removal of TSS could be positively correlated to the E. coli removal for the AGS technology at the evaluated WWTPs., Graphical abstract Image 1, Highlights • No difference in removal efficiencies (α = 5%) of FIOs was found for the studied AGS and CAS systems. • 1.3 to 2.1 Log10 removals for F-specific RNA bacteriophages were found for the CAS and AGS systems. • 1.1 to 2.3 Log10 removals for E. coli, Enterococci, and TtC were obtained for the AGS and CAS systems. • The two stage CAS performed better than the carrousel CAS in removing F-specific RNA bacteriophages. • A positive correlation was found between the TSS and E. coli removal, and COD and TtC removal in the AGS systems.

The use of saline water in urban areas for non-potable purposes to cope with fresh water scarcity, intrusion of saline water, and disposal of industrial saline wastewater into the sewerage lead to elevated salinity levels in wastewaters. Consequently, saline wastewater is generated, which needs to be treated before its discharge into surface water bodies. The objective of this research was to study the effects of salinity on the aerobic metabolism of phosphate-accumulating organisms (PAO), which belong to the microbial populations responsible for enhanced biological phosphorus removal (EBPR) in activated sludge systems. In this study, the short-term impact (hours) of salinity (as NaCl) was assessed on the aerobic metabolism of a PAO culture, enriched in a sequencing batch reactor (SBR). All aerobic PAO metabolic processes were drastically affected by elevated salinity concentrations. The aerobic maintenance energy requirement increased, when the salinity concentration rose up to a threshold concentration of 2 % salinity (on a W/V basis as NaCl), while above this concentration, the maintenance energy requirements seemed to decrease. All initial rates were affected by salinity, with the NH4- and PO4-uptake rates being the most sensitive. A salinity increase from 0 to 0.18 % caused a 25, 46, and 63 % inhibition of the O2, PO4, and NH4-uptake rates. The stoichiometric ratios of the aerobic conversions confirmed that growth was the process with the highest inhibition, followed by poly-P and glycogen formation. The study indicates that shock loads of 0.18 % salt, which corresponds to the use or intrusion of about 5 % seawater may severely affect the EBPR process already in wastewater treatment plants not exposed regularly to high salinity concentrations.

Aims Sulphate-reducing bacteria (SRB) activity is generally considered as inconvenience in domestic wastewater treatment plants (WWTP), but could also be applied beneficially. The competition between SRB and methanogens is a point of concern for stable process design. As limited attention was given to the effect of varying acetate and propionate concentrations on SRB activity, this study focused specially on these substrates. Methods and results The research was performed in sequencing batch reactors operated at 20°C and an SRT of 15 days. In the acetate-fed reactor, methanogens became dominant, while in the propionate reactor, SRB were the dominant population. In the mixed-substrate-fed reactor, both substrates were converted by SRB. The dominant SRB population in the mixed-substrate-fed reactor was different from the propionate-fed reactor, but all operational characteristics such as the substrate consumption rate, yield and growth rate were similar. The sludge adapted to propionate could easily switch to an acetate feed procedure. Conclusions These results indicate that under wastewater temperature of 20°C, the SRB are likely to outcompete methanogens more easily as inferred from pure substrate studies on acetate solely. Significance and impact of the study The present results show that the natural presence of propionate in wastewater allows stable sulphate reduction, which decreases the biogas production, but provides an opportunity for using SRB beneficially in wastewater treatment.

The use of saline water as secondary quality water in urban environments for sanitation is a promising alternative towards mitigating fresh water scarcity. However, this alternative will increase the salinity in the wastewater generated that may affect the biological wastewater treatment processes, such as biological phosphorus removal. In addition to the production of saline wastewater by the direct use of saline water in urban environments, saline wastewater is also generated by some industries. Intrusion of saline water into the sewers is another source of salinity entering the wastewater treatment plant. In this study, the short-term effects of salinity on the anaerobic metabolism of phosphate-accumulating organisms (PAO) and glycogen-accumulating organisms (GAO) were investigated to assess the impact of salinity on enhanced biological phosphorus removal. Hereto, PAO and GAO cultures enriched at a relatively low salinity level (0.02 % W/V) were exposed to salinity concentrations of up to 6 % (as NaCl) in anaerobic batch tests. It was demonstrated that both PAO and GAO are affected by higher salinity levels, with PAO being the more sensitive organisms to the increasing salinity. The maximum acetate uptake rate of PAO decreased by 71 % when the salinity increased from 0 to 1 %, while that of GAO decreased by 41 % for the same salinity increase. Regarding the stoichiometry of PAO, a decrease in the P-release/HAc uptake ratio accompanied with an increase in the glycogen consumption/HAc uptake ratio was observed for PAO when the salinity increased from 0 to 2 % salinity, indicating a metabolic shift from a poly-P-dependent to a glycogen-dependent metabolism. The anaerobic maintenance requirements of PAO and GAO increased as the salinity concentrations risen up to 4 % salinity.

Seawater toilet flushing, seawater intrusion in the sewerage, and discharge of sulfate-rich industrial effluents elevates sulfate content in wastewater. The application of sulfate-reducing bacteria (SRB) in wastewater treatment is very beneficial; as for example, it improves the pathogen removal and reduces the volume of waste sludge, energy requirement and costs. This paper evaluates the potential to apply biological sulfate reduction using acetate and propionate to saline sewage treatment in moderate climates. Long-term biological sulfate reduction experiments at 10 and 20 °C were conducted in a sequencing batch reactor with synthetic saline domestic wastewater. Subsequently, acetate and propionate (soluble organic carbon) conversion rate were determined in both reactors, in the presence of either or both fatty acids. Both acetate and propionate consumption rates by SRB were 1.9 times lower at 10 °C than at 20 °C. At 10 °C, propionate was incompletely oxidized to acetate. At 10 °C, complete removal of soluble organic carbon requires a significantly increased hydraulic retention time as compared to 20 °C. The results of the study showed that biological sulfate reduction can be a feasible and promising process for saline wastewater treatment in moderate climate.

The occurrence of Accumulibacter Type I (a known phosphorus-accumulating organism, PAO) has received increased attention due to the potential operating benefits associated with their denitrifying activity in enhanced biological phosphorus removal (EBPR) wastewater treatment plants. In this study, after a shift from an enriched glycogen-accumulating organism (GAO) culture (competitors of PAO) to a PAO-enriched system, Accumulibacter Type I (PAO I) became dominant in an anaerobic-aerobic EBPR system fed with acetate and operated at 10°C with a net aerobic solids retention time (SRT) of 6 d. Since Accumulibacter Type II (PAO II) were not detected, the low temperature in combination with the net aerobic SRT applied appeared to have suppressed their growth as well. The stoichiometry of PAO I was in agreement with previous metabolic models, suggesting that it was the main PAO organisms present in previous studies operated under similar conditions. Moreover, under poly-P limiting conditions, PAO I were unable to switch to a GAO-like metabolism at low temperatures. These results contribute to increase the understanding of the physiology, microbial metabolism and microbial ecology of PAO I.

The overall performance of the Anjana wastewater treatment plant (WWTP) located in Surat, India, was assessed by coupling the Activated Sludge Model No. 3 (ASM3) and the Anaerobic Digestion Model No. 1 (ADM1). Guidelines developed by the Dutch Foundation for Applied Water Research (STOWA) were successfully applied for the determination of wastewater characteristics. Concerning the fractionation of primary and secondary sludge, the approach proved to be adequate for the application of ADM1. A satisfactory description of the performance of the plant was obtained in terms of effluent quality, biogas generation and sludge production. This was achieved through coupling ASM3 with ADM1 and adjusting four default values (the growth of autotrophic bacteria from 1 to 0.46 day−1, influent fraction of unbiodegradable particulate chemical oxygen demand (COD) to 0.14 gCOD/gCOD, and the anaerobic disintegration factors for soluble and particulate unbiodegradable COD in ADM1 to 0.01 and 0.29 gCOD/gCOD, respectively). The model was applied to optimise the plant performance and to assess the potential influence of the return of high strength reject effluents through the implementation of an ADM1-ASM3 interface. This study underlines the feasibility, advantages and benefits of mathematical modelling as a reliable tool for process optimisation, plant upgrade and resource recovery in developing countries.

The objective of this study was to investigate the ability of a culture highly enriched with the polyphosphate-accumulating organism, 'Candidatus Accumulibacter phosphatis' clade IIC, to adjust their metabolism to different phosphate availabilities. For this purpose the biomass In six different experimental phases, the biomass was cultivated in a sequencing batch reactor with acetate and exposed to at different phosphate/carbon influent ratios during six experimental phases. Activity tests were conducted to determine the anaerobic kinetic and stoichiometric parameters as well as the composition of the microbial community. Increasing influent phosphate concentrations led to increased poly-phosphate content and decreased glycogen content of the biomass. In response to higher biomass poly-phosphate content, the biomass showed higher Faster active biomass specific phosphate release rates were observed as biomass poly-phosphate content increased. Together with the phosphate release rates, acetate uptake rates also increased up to an optimal poly-phosphate/glycogen ratio of 0.3 P-mol/C-mol at which the organisms were most competitive. At higher poly-phosphate/glycogen ratios (obtained at influent P/C ratios above 0.051 P-mol/C-mol)ratios, the acetate uptake rates started to decrease. The stoichiometry of the anaerobic conversions clearly demonstrated a metabolic shift from a glycogen dominated to a poly-phosphate dominated metabolism as the biomass poly-phosphate content increased. FISH and DGGE analyses confirmed that no significant changes occurred in the microbial community, suggesting that the changes in the biomass activity were due to different metabolic behavior, allowing the organisms to proliferate under conditions with fluctuating phosphate levels.

Although simultaneous P-removal and nitrate reduction has been observed in laboratory studies as well as full-scale plants, there are contradictory reports on the ability of PAO I to efficiently use nitrate as electron acceptor. Such discrepancy could be due to other microbial groups performing partial denitrification from nitrate to nitrite. The denitrification capacities of two different cultures, a highly enriched PAO I and a PAO I-GAO cultures were assessed through batch activity tests conducted before and after acclimatization to nitrate. Negligible anoxic phosphate uptake coupled with a reduction of nitrate was observed in the highly enriched PAO I culture. On the opposite, the PAO I-GAO culture showed a higher anoxic phosphate uptake activity. Both cultures exhibited good anoxic phosphate uptake activity with nitrite (8.7 ± 0.3 and 9.6 ± 1.8 mgPO4-P/gVSS.h in the PAO I and PAO I-GAO cultures, respectively). These findings suggest that other microbial populations, such as GAOs, were responsible to reduce nitrate to nitrite in this EBPR system, and that PAO I used the nitrite generated for anoxic phosphate uptake. Moreover, the simultaneous denitrification and phosphate removal process using nitrite as electron acceptor may be a more sustainable process as can: i) reduce the carbon consumption, ii) reduce oxygen demand of WWTP, and iii) due to a lower growth yield contribute to a lower sludge production.

Toilet facilities in highly dense areas such as the slum and emergency settlements fill up rapidly; thus, requiring frequent emptying. Consequently, big quantities of fresh faecal sludge (FS) containing large amounts of pathogens are generated. Fast and efficient FS treatment technologies are therefore required for safe treatment and disposal of the FS in such conditions. This study explores the applicability of a microwave (MW) technology for the treatment of fresh FS obtained from urine-diverting dry toilets placed in slum settlements in Nairobi, Kenya. Two sample fractions containing 100 g and 200 g of FS were exposed to MW irradiation at three input MW power levels of 465, 1085 and 1550 W at different exposure times ranging from 0.5 to 14 min. The variation in the FS temperature, pathogen reduction via the destruction of E. coli and Ascaris lumbricoides eggs, and vol/wt reduction were measured during the MW treatment. It was demonstrated that the MW technology can rapidly and efficiently achieve complete reduction of E. coli and Ascaris lumbricoides eggs, and over 70% vol/wt reduction in the fresh FS. Furthermore, the successful evaluation of the MW technology under real field conditions demonstrated that MW irradiation can be applied for rapid treatment of fresh FS in situations such as urban slum and emergency conditions., Graphical abstract Image 1, Highlights • There is lack of appropriate options to treat sludge from intensively used toilets. • Microwave treatment is fast and efficient in sludge volume and pathogen reduction. • Microwave technology can be applied to treat fecal sludge in slums and emergencies.

Providing safe excreta disposal following disasters is important for disease prevention and the safety and dignity of the affected population. This is challenging because every emergency varies due to the nature of the disaster, local conditions and the characteristics of the affected population. This paper investigates the impact of the 2006 Java earthquake on excreta disposal needs and the response to those needs. Relevant documents were retrieved from the ReliefWeb database, complemented by a literature search. The case study highlights gaps in rapidly providing latrines on a large scale. Three months after the disaster, only 57% of the latrines targeted had been provided. One way to address this problem is to better understand the factors affecting excreta disposal needs and response, allowing appropriate solutions to be identified more effectively.

"Plus d'un milliard de personnes dans les zones urbaines et periurbaines d'Afrique, d'Asie et d'Amerique latine sont desservies par des dispositifs d'assainissement a la parcelle. La gestion des boues extraites de ces dispositifs, les « boues de vidange », a ete jusqu'a present grandement negligee. Les ressources financieres sont souvent insuffisantes et les dispositifs d'assainissement a la parcelle ont tendance a etre consideres comme des solutions temporaires, dan l'attente de la mise en place de reseaux d'egouts. Cependant , force est de constater que l'assainissement a la parcelle est la pour durer, soit en tant que solution autonome permanente, soit en association avec des systemes egouts-station. La gestion adequate des boues de vidange issues des dispositifs d'assainissement des menages est un imperatif pour la protection de Ia sante humaine et de l'environnement. Cet ouvrage est le premier a etre consacre a la gestion des boues de vidange. II rassemble l'etat actuel des connaissances de ce domaine qui evolue rapidement, et propose une approche integree qui lie les composantes technologiques, organisationnelles et de planification. II aborde la planification et l'organisation de l'ensemble de la filiere de gestion des boues de vidange depuis la collecte et l'evacuation des boues jusqu'aux solutions de traitement et a l'utilisation finale ou la mise en depot des boues traitees. En plus de fournir des elements fondamentaux sur le traitement et une description des technologies existantes, l'ouvrage presente en detail les aspects operationnels, institutionnels et financiers. II propose egalement une methode de planification d'un projet de gestion des boues de vidange a l'echelle d'une ville avec l'ensemble des parties prenantes."

In 1982 the International Association on Water Pollution Research and Control (IAWPRC), as it was then called, established a Task Group on Mathematical Modelling for Design and Operation of Activated Sludge Processes. The aim of the Task Group was to create a common platform that could be used for the future development of models for COD and N removal with a minimum of complexity. As the collaborative result of the work of several modelling groups, the Activated Sludge Model No. 1 (ASM1) was published in 1987, exactly 25 years ago. The ASM1 can be considered as the reference model, since this model triggered the general acceptance of wastewater treatment modelling, first in the research community and later on also in practice. ASM1 has become a reference for many scientific and practical projects, and has been implemented (in some cases with modifications) in most of the commercial software available for modelling and simulation of plants for N removal. The models have grown more complex over the years, from ASM1, including N removal processes, to ASM2 (and its variations) including P removal processes, and ASM3 that corrects the deficiencies of ASM1 and is based on a metabolic approach to modelling. So far, ASM1 is the most widely applied. Applications of Activated Sludge Models has been prepared in celebration of 25 years of ASM1 and in tribute to the activated sludge modelling pioneer, the late Professor G.v.R. Marrais. It consists of a dozen of practical applications for ASM models to model development, plant optimization, extension, upgrade, retrofit and troubleshooting, carried out by the members of the Delft modelling group over the last two decades. ISBN: 9781780404660 (eBook) ISBN: 9781780404639 (Print)