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A novel system was used for nitrogen removal from reject water. This system includes one anoxic/oxic reactor for nitrification and a special reactor for denitrification in which primary sludge was added intermittently as electron donor. In denitrification reactor, sludge fermentation and denitrification reaction took place simultaneously and promoted each other. It was found that effluent recycle could improve nitrogen removal efficiency due to reclaiming of alkalinity. Under steady state conditions, the average solid retention time (SRT) in denitrification reactor was 12-15 d, a total nitrogen loading rate was 0.2 kg N/(m³ day) and TN removal efficiency was more than 90% without extra carbon source addition. Primary sludge was degraded so that volatile suspended solid (VSS) decreased by 50%. Further investigation showed that ORP could be taken as a control parameter for sludge addition. [ABSTRACT FROM AUTHOR]

Natural resources are under worldwide pressure, water and sustainable energy being the paramount issues. Haemodialysis, a water-voracious and energy-hungry healthcare procedure, thoughtlessly wastes water and leaves a heavy carbon footprint. In our service, 100 000 L/week of previously discarded reverse osmosis reject water – water which satisfies all World Health Organisation criteria for potable (drinking) water – no longer drains to waste but is captured for reuse. Reject water from the hospital-based dialysis unit provides autoclave steam for instrument sterilization, ward toilet flushing, janitor stations and garden maintenance. Satellite centre reject water is tanker-trucked to community sporting fields, schools and aged-care gardens. Home-based nocturnal dialysis patient reuse reject water for home domestic utilities, gardens and animal watering. Although these and other potential water reuse practices should be mandated through legislation for all dialysis services, this is yet to occur. In addition, we now are piloting the use of solar power for the reverse osmosis plant and the dialysis machines in our home dialysis training service. If previously attempted, these have yet to be reported. After measuring the power requirements of both dialytic processes and modelling the projected costs, a programme has begun to solar power all dialysis-related equipment in a three-station home haemodialysis training unit. Income-generation with the national electricity grid via a grid-share and reimbursement arrangement predicts a revenue stream back to the dialysis service. Dialysis services must no longer ignore the non-medical aspects of their programmes but plan, trial, implement and embrace ‘green dialysis’ resource management practices. [ABSTRACT FROM AUTHOR]

Abstract: Reject water, which is the liquid fraction produced after dewatering of anaerobically digested activated sludge on the municipal wastewater treatment plants (MWWTPs), contributes up to 80% of the nitrogen and phosphorus loads to the MWWTP. It was proposed to combine the removal of nitrogen from reject water using the sequential biooxidation of and bioreduction of with precipitation of phosphate by Fe2+ ions produced due to bioreduction of Fe3+ in iron ore. Bioreduction of decreased Fe3+ bioreduction rate in reject water from 37 to 21mg Fe2+/Ld due to competition between and Fe3+ for electron donors. Addition of acetate as electron donor increased both bioreduction rates of Fe3+ and but acetate interfered with the competition between nitrate and phosphate anions reacting with ferrous cations decreasing efficiency of the phosphate removal from reject water. The stages of denitrification and ferric bioreduction/phosphate precipitation must be performed sequentially. [Copyright &y& Elsevier]

The Olburgen sewage treatment plant has been upgraded to improve the effluent quality by implementing a separate and dedicated treatment for industrial (potato) wastewater and reject water. The separate industrial treatment has been realized within a beneficial public-private partnership. The separate treatment of the concentrated flows of industrial wastewater and sludge treatment effluent proved to be more cost-efficient and area and energy efficient than a combined traditional treatment process. The industrial wastewater was first treated in a UASB reactor for biogas production. The UASB reactor effluent was combined with the reject water and treated in a struvite reactor (Phospaq process) followed by a one stage granular sludge nitritation/anammox process. For the first time both reactors where demonstrated on full scale and have been operated stable over a period of 3 years. The recovered struvite has been tested as a suitable substitute for commercial fertilizers. Prolonged exposure of granular anammox biomass to nitrite levels up to 30 mg/l did not result in inhibition of the anammox bacteria in this reactor configuration. The chosen option required a 17 times smaller reactorvolume (20,000 m3 less volume) and saves electric power by approximately 1.5 GWh per year. [ABSTRACT FROM AUTHOR]

Deammonification involves the combined application of aerobic and anoxic ammonium-oxidizing bacteria (AerAOB & AnAOB) and allows to treat wastewaters with a high ammonium concentration in a sustainable and cost-efficient way. So far, it could take more than one year to start up the process, even with the addition of AnAOB enriched inocula. In contrast, we started up a deammonifying reactor for the treatment of sludge digestate in less than four months without any AnAOB enriched inoculum. In a single sequencing batch reactor (SBR) of 3m3, nitritation and anammox were performed without nitrite accumulation. Larger biomass aggregates (>1.0mm) had a typical reddish colour, but FISH also showed that small aggregates (>0.25mm) contained a considerable amount of AnAOB. The AerAOB were related to Nitrosomonas halophila, N. eutropha and N. halophila, and the AnAOB to "Candidatus Kuenenia & Brocadia", as shown by FISH. Our results show that the deammonification inoculum does not play an important role, and that the AnAOB can quickly develop under the proper aerational conditions. Nitrogen was removed stably at high nitrogen loading rates (740mgN/L/d) and removal efficiency (90%). [ABSTRACT FROM AUTHOR]

Abstract: Impact of reject brine chemical composition on soils in Riyadh Saudi Arabia, was evaluated. Soil samples at three depths along transect on both sides of the pond were taken, in addition to, water samples from feed, product, reject and pond. Results showed that, the salinity of the brine reached up to, 5500mgl−1. The concentrations of soluble ions were exceeding the allowable limits in most water samples. The ratio of major ions and concentration factor was higher. The concentrations of heavy metals were in the allowable limits for drinking water standards especially, in the feed, and product waters. Results pertaining soil properties indicated that the soil pH, ECe values and, the concentrations of soluble ions were higher in soils closed to the pond. Also, the concentrations of heavy metals were negatively correlated with CaCO3 content and soil pH (expect for Pb; Zn; Cd and Cr), while it was highly correlated with clay content of the soil. Generally, higher ESP and ECe values in the studied soils can lead to lower permeability, poor aeration and consequently soil deterioration. [Copyright &y& Elsevier]

In view of the well recognized need of reject water treatment in MWWTP (municipal wastewater treatment plant), this paper outlines two strategies for P removal from reject water using alum sludge, which is produced as by-product in drinking water treatment plant when aluminium sulphate is used for flocculating raw waters. One strategy is the use of the alum sludge in liquid form for co-conditioning and dewatering with the anaerobically digested activated sludge in MWWTP. The other strategy involves the use of the dewatered alum sludge cakes in a fixed bed for P immobilization from the reject water that refers to the mixture of the supernatant of the sludge thickening process and the supernatant of the anaerobically digested sludge. Experimental trials have demonstrated that the alum sludge can efficiently reduce P level in reject water. The co-conditioning strategy could reduce P from 597--675mgP/L to 0.14--3.20mgP/L in the supernatant of the sewage sludge while the organic polymer dosage for the conditioning of the mixed sludges would also be significantly reduced. The second strategy of reject water filtration with alum sludge bed has shown a good performance of P reduction. The alum sludge has P-adsorption capacity of 31 mg-P/g-sludge, which was tested under filtration velocity of 1.0 m/h. The two strategies highlight the beneficial utilization of alum sludge in wastewater treatment process in MWWTP, thus converting the alum sludge as a useful material, rather than a waste for landfill [ABSTRACT FROM AUTHOR]

A laboratory-scale bioreactor study was conducted to characterize differences in nitrification function in main-stream reactors due to bioaugmentation from side-stream reactors treating reject water. The objective was to evaluate how configuration of a suspended growth side-stream bioreactor impacts nitrification function in the main-stream bioreactor. A bioaugmentation effect was not observed in main-stream reactors operated at warm temperatures. Complete oxidation of ammonia to nitrate was observed in the bioaugmented and control main-stream reactors although nitrite accumulation was observed in each case. Furthermore, respirometry did not reveal superior kinetics in bioaugmented reactors operated at warm temperatures. At cold temperatures bioaugmentation may have stabilized ammonia oxidation in main-stream reactor B2 bioaugmented from a PFR side-stream. Complete ammonia oxidation was observed for most of cold period of operation in the main-stream bioreactor B2. Furthermore, respirometry revealed a higher rate of ammonia oxidation and more stable nitrite oxidation compared with the control bioreactor. [ABSTRACT FROM AUTHOR]

Abstract: The removal of phosphorus from reject water, which is the liquid fraction produced after dewatering of anaerobically digested activated sludge on the municipal wastewater treatment plants (MWWTPs), can significantly reduce the phosphorus load to the main stream of the MWWTPs. Ferric or ferrous reagents can be used for this removal but the significantly cheaper option could be the production of ferrous reagent using bioreduction of iron ore. The removal of phosphorus from reject water using anoxic bioreduction of iron ore was studied in the rotating reactor, which was selected to avoid the clogging of the pores between iron ore particles. The highest phosphorus removal rate from reject water in the rotating reactor, i.e. the parameter which can be used in the design of the continuous process, was 25mg P/Lday. Significant role in the iron ore bioreduction is playing the formation of the fine particles from initially loaded coarse particles of iron ore during rotation of the reactor. [Copyright &y& Elsevier]

This study investigated the performance of a one-stage partial nitritation-anammox (PN/A) system for the treatment of reject water from high-solid-sludge anaerobic digestion with thermal hydrolysis pretreatment (THP-AD). The proportion of reject water was gradually increased (10.8%, 23.2%, 36.4%, 73.7% and 100%) during the 90-day operation. The nitrogen loading rate (NLR) reached 0.44 kg N/m3/d using 73.7% reject water as influent, while it decreased to only 0.15 kg N/m3/d with 100% reject water. Meanwhile, sludge particles with diameters < 180 µm became the largest granulometric fraction. Microbial community structure analysis indicated that the relative abundances of functional microorganisms became extremely low; e.g., 0.05% and 0.5% for Nitrosomonas and Candidatus Brocadia, respectively. An additional 47-day experiment was performed using only the anammox stage to evaluate the inhibition impacts of organics. This was fed with reject water with partial ammonia nitrogen stripping and nitrite nitrogen addition for the first 38 days and PN-treated reject water for days 39–47. Reject water with an 80% raw organic content demonstrated severe inhibition, with the NLR dropping from 1.27 kg N/m3/d to 0.27 kg N/m3/d. This, could be partially restored to 0.93 kg N/m3/d when the influent was pretreated by PN. It appears that the biodegradable organic matter inhibited the one-stage PN/A system more than the non-biodegradable fraction. After removal of biodegradable organics, the NRR of the anammox system recovered, indicating that two-stage PN/A has greater advantages in THP-AD reject water treatment than a one-stage PN/A system. [Display omitted] • Decreasing dilution of THP-AD reject water in the influent reduced one-stage PN/A activity. • Degranulation of granular anammox sludge occurred when treating THP-AD reject water. • The abundance of AOB and AMX bacteria was low when treating undiluted THP-AD. • PN pretreatment alleviated inhibition of anammox activity. • SCOD value couldn't directly explain the inhibition of anammox activity. [ABSTRACT FROM AUTHOR]

Recycling vital macronutrients, such as nitrogen, from wastewaters back to fertiliser use is becoming essential to ensure sustainable agricultural practices. Technologies developed for such purposes are typically evaluated for their capacity to recover nutrients; however, the presence of contaminants of emerging concern (CECs) in these waste-derived nutrient products must not be overlooked. In this study, nitrogen was recovered from real anaerobically digested municipal sewage sludge reject water using a novel set-up combining membrane-based electroconcentration (EC) with electrochemical advanced oxidation processes (EAOPs). Simultaneously, the fate of five spiked pharmaceuticals (carbamazepine, ciprofloxacin, diclofenac, erythromycin and metoprolol) as well as ten indigenous perfluoroalkyl substances (PFASs) was investigated. The EC-EAOP system was effective in up-concentrating nitrogen ca. 13 times to a final concentration of 12.7 ± 0.8 g L−1 in the nutrient product. At the same time, no up-concentration was observed for the pharmaceuticals and their concentrations in the recovered concentrated remained at ≤ 3.4 ± 1.3 µg L−1. The EAOPs were the main transformation mechanism for all the pharmaceuticals at 33–88% efficiency, while diclofenac also notably adsorbed in the system (30 ± 1.4%). Out of the ten studied PFASs, only three were found in the recovered nutrient concentrate, albeit at very limited concentrations of ≤ 0.024 ± 0.013 µg L−1. The EAOPs were found to degrade longer-chain PFASs into their shorter-chain counterparts. The low contaminant concentrations in the nutrient product pose a reduced risk for soil contamination compared to, e.g., biosolids that are more typically used as fertilisers. [Display omitted] • The fate of pharmaceuticals and PFASs was studied during nitrogen recovery. • Ion-exchange membranes efficiently retained all studied contaminants. • 33–88% of pharmaceuticals were transformed by electrochemical advanced oxidation. • Long-chain PFASs were oxidised to their shorter-chain counterparts. • The nutrient product contained less contaminants than, e.g., biosolids. [ABSTRACT FROM AUTHOR]

Despite a global focus on resource conservation, most hemodialysis (HD) services still wastefully or ignorantly discard reverse osmosis (R/O) “reject water” (RW) to the sewer. However, an R/O system is producing the highly purified water necessary for dialysis, it rejects any remaining dissolved salts from water already prefiltered through charcoal and sand filters in a high-volume effluent known as RW. Although the RW generated by most R/O systems lies well within globally accepted potable water criteria, it is legally “unacceptable” for drinking. Consequently, despite being extremely high-grade gray water, under current dialysis practices, it is thoughtlessly “lost-to-drain.” Most current HD service designs neither specify nor routinely include RW-saving methodology, despite its simplicity and affordability. Since 2006, we have operated several locally designed, simple, cheap, and effective RW collection and distribution systems in our in-center, satellite, and home HD services. All our RW water is now recycled for gray-water use in our hospital, in the community, and at home, a practice that is widely appreciated by our local health service and our community and is an acknowledged lead example of scarce resource conservation. Reject water has sustained local sporting facilities and gardens previously threatened by indefinite closure under our regional endemic local drought conditions. As global water resources come under increasing pressure, we believe that a far more responsible attitude to RW recycling and conservation should be mandated for all new and existing HD services, regardless of country or region. [ABSTRACT FROM AUTHOR]

This paper presents benefits and potential drawbacks of thermal pre-hydrolysis of sewage sludge from an operator's prospective. The innovative continuous Thermo-Pressure-Hydrolysis Process (TDH) has been tested in full-scale at Zirl wastewater treatment plant (WWTP), Austria, and its influence on sludge digestion and dewatering has been evaluated. A mathematical plant-wide model with application of the IWA Activated Sludge Model No.1 (ASM1) and the Anaerobic Digestion Model No.1 (ADM1) has been used for a systematic comparison of both scenarios— operational plant performance with and without thermal pre-hydrolysis. The impacts of TDH prehydrolysis on biogas potential, dewatering performance and return load in terms of ammonia and inert organic compounds (Si) have been simulated by the calibrated model and are displayed by Sankey mass flow figures. Implementation of full scale TDH process provided higher anaerobic degradation efficiency with subsequent increased biogas production (+75-80%) from waste activated sludge (WAS). Both effects—enhanced degradation of organic matter and improved cake's solids content from 25.2 to 32.7% TSS—promise a reduction in sludge disposal costs of about 25%. However, increased ammonia release and generation of soluble inerts Si was observed when TDH process was introduced. [ABSTRACT FROM AUTHOR]

An efficient biological treatment to treat reject water from anaerobic digestion of wastewater sludge is the SHARON denitrification process, which takes place in a chemostat reactor, where aerobic/anoxic periods are alternated under specific hydraulic retention time (HRT) and temperature conditions that favor ammonium oxidizers growth and ensure the total washout of nitrite oxidizers, achieving the biological nitrogen removal over nitrite. An optimized performance of this process to treat Spanish reject water was obtained using methanol and working at an HRT of 2 days, 33°C, and cycle length of 2 hours. Supernatant of hydrolyzed primary sludge was tested to denitrify. Because biochemical oxygen demand was not extremely high in the primary sludge, the fluid dynamics of the system were changed, with respect to the strategy with methanol, but maintaining the reject water influent flowrate. The use of hydrolyzed primary sludge improved the process efficiency, because the alkalinity present in the primary sludge buffered the process until an optimum pH range. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this study was the operation and model description of a sequencing batch reactor (SBR) for biological nitrogen removal (BNR) from a reject water ) from a municipal wastewater treatment plant (WWTP). The SBR was operated with three cycles per day, temperature 30°C, SRT 11days and HRT 1day. During the operational cycle, three alternating oxic/anoxic periods were performed to avoid alkalinity restrictions. Oxygen supply and working pH range were controlled to achieve the BNR via nitrite, which makes the process more economical. Under steady state conditions, a total nitrogen removal of 0.87kg N (m3 day)−1 was reached. A four-step nitrogen removal model was developed to describe the process. This model enlarges the IWA activated sludge models for a more detailed description of the nitrogen elimination processes and their inhibitions. A closed intermittent-flow respirometer was set up for the estimation of the most relevant model parameters. Once calibrated, model predictions reproduced experimental data accurately. [Copyright &y& Elsevier]

Abstract: A comparative study to produce the correct influent for Anammox process from anaerobic sludge reject water (700–800mg NH4 +-NL−1) was considered here. The influent for the Anammox process must be composed of NH4 +-N and NO2 −-N in a ratio 1:1 and therefore only a partial nitrification of ammonium to nitrite is required. The modifications of parameters (temperature, ammonium concentration, pH and solid retention time) allows to achieve this partial nitrification with a final effluent only composed by NH4 +-N and NO2 −-N at the right stoichiometric ratio. The equal ratio of HCO3 −/NH4 + in reject water results in a natural pH decrease when approximately 50% of NH4 + is oxidised. A Sequencing batch reactor (SBR) and a chemostat type of reactor (single-reactor high activity ammonia removal over nitrite (SHARON) process) were studied to obtain the required Anammox influent. At steady state conditions, both systems had a specific conversion rate around 40mg NH4 +-Ng−1 volatile suspended solids (VSS)h−1, but in terms of absolute nitrogen removal the SBR conversion was 1.1kgNday−1 m−3, whereas in the SHARON chemostat was 0.35kgNday−1 m−3 due to the different hydraulic retention time (HRT) used. Both systems are compared from operational (including starvation experiments) and kinetic point of view and their advantages/disadvantages are discussed. [Copyright &y& Elsevier]

Nitrification is the rate-limiting process in the design of activated sludge process. It is especially unstable during the winter season (when the temperature of activated sludge mixed liquor drops below 13°C). It is therefore difficult to meet the ammonia effluent standards in winter. The common way to compensate for low nitrification rates at low temperatures is to increase sludge retention time (SRT). However, the increase of SRI is accompanied by negative factors such as elevated sludge concentration, higher sludge loading of secondary clarifiers, formation of unsettleable microflocs, etc. The low performance of nitrification at low temperatures can also be compensated for by enhancing the nitrification population in activated sludge. This paper describes such a method called bioaugmentation of nitrification in situ. This procedure takes place in a so-called regeneration tank, which is situated in the return activated sludge stream. The results of the operation of two wastewater treatment plants with regeneration zones are described in this paper, together with some economic evaluation of the bioaugmentation method. [ABSTRACT FROM AUTHOR]

Reject water from sewage sludge processing may contain high concentrations of nutrients and organic pollutants and cause internal pollution load at a sewage treatment plant (STP) if circulated to the headworks of an STP. In the present study removal of nitrogen and bis (2-ethylhexyl) phthalate (DEHP) from reject water was studied in two sequencing batch reactors (SBRs) with different aerobic/anoxic periods during a 6-h total cycle period. Ammonia-nitrogen (NH4-N) was almost totally removed in both reactors, apparently by nitrification throughout the run, while denitrification declined with decreasing SCOD in the influent resulting in an increase in the effluent nitrate-nitrogen (NO3-N) concentration. DEHP removals from the water phases were above 95% in both reactors, while the average total removals were 36 and 42%, calculated on a mass basis. Much higher removals occurred in the experiment where one of the systems was spiked with a given amount of DEHP. The spiking experiment suggested that SBRs had the potential to remove DEHP biologically from reject water but that the removal was restricted by the poor bioavailability of DEHP as a result of sorption to solids. This study showed that SBR has the potential to cut the internal load of nitrogen and hydrophobic organic pollutants in cases where reject water is circulated to the headworks of an STP. [Copyright &y& Elsevier]

The increase of the hydraulic loading of a municipal wastewater treatment plant caused by the sludge dewatering process is of minor importance. However, the rejected nitrogen load accounts for up to 25% of the nitrogen load in the raw sewage. As a result, the process water significantly influences the stage volume of the biological treatment steps. Rejection management can prevent critical nitrogen concentrations in the effluent of the plant. In some cases, the treating capacity must be increased. Separate treatment of the process water can be an alternative to the enlargement of the main wastewater treatment stages. This article describes the compositions of the process waters from different sludge treatment steps, the influence on the main wastewater treatment steps, possible strategies to handle the rejection problem, and processes for separate treatment of the sludge liquor. Some results of a German case study on large wastewater treatment plants illustrate the situation concerning separate process water treatment in Germany. These results suggest that side stream treatment can be a practical alternative to a classic increase in the length of the main stream stages. Moreover, they prove that many different processes are useful for the separate treatment of sludge liquor. [ABSTRACT FROM AUTHOR]

Separate biological elimination of nitrogen from the digester supernatant of a municipal wastewater treatment plant (WWTP) was investigated in pilot and full-scale plants. Denitrification mainly via nitrite was achieved in a sequencing batch reactor (SBR) and a continuous flow reactor (CSTR or SHARON). Suppression of nitrite oxidation in the SBR was feasible at short aerobic/anaerobic intervals allowing for immediate denitrification of the produced nitrite. Nitrate production could also be stopped by exposing the biomass to anaerobic conditions for 11 days. Temporarily high concentrations (up to 80 gNH3-Nm-3>>>>>>>>>>>>>>>>>>>>) of free ammonia could not be considered as the major reason for inhibiting nitrite oxidation. In a fullscale SBR plant 90% of the nitrogen load was denitrified in a total hydraulic retention time (HRT) of 1.6 days and with a sludge age between 15 and 20 days. Ethanol and methanol were used for denitrification. The specific average substrate consumption was 2.2 gCODdosedg-1N removed with an effective biomass yield of 0.2 gCODbiomassg-1CODdosed>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>. No dosing with base was required. In the SHARON process full nitrogen elimination was achieved only with a total HRT greater than 4 days at 29°C. The overall costs were estimated at €1.4 kg-1Nremoved>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> for the SBR and €1.63 kg-1Nremoved>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> in SHARON mode, respectively. The SHARON process is simple in operation (CSTR) but the tank volume has to be significantly greater than in SBR. [ABSTRACT FROM AUTHOR]

Reject water separated from digested sludge may be a potential source of nutrients due to its high content. However, most often, reject water after sludge dewatering is directed to sewage lines at wastewater treatment plants, negatively affecting their operation, especially in the biological part. The activities related to sludge conditioning before dewatering have a direct impact on the quality of the reject water. The reject water of raw digested sludge is characterized by very high concentrations of ammonium nitrogen, at 1718 mgN-NH4+/dm3; phosphates, at 122.4 mgPO43−/dm3; and chemical oxygen demand (COD), at 2240 mgO2/dm3. The objective of the research was to determine the impact of selected sludge conditioning methods on the quality of reject water obtained after sludge dewatering. The following parameters were analyzed in the reject water: the chemical oxygen demand (COD), phosphates, ammonium nitrogen, and total suspended solids (TSS). It has been observed that the sludge sonification process increases the content of impurities (COD, phosphates) in reject water with an increase in the amplitude of the ultrasonic field. On the other hand, the chemical reagents cause a decrease in the concentration of the pollutants with an increase of the chemical dose. It has been found that the inorganic coagulant PIX 113 gives much better results regarding the reduction of contamination than the polyelectrolyte Zetag 8180. [ABSTRACT FROM AUTHOR]

Conventional two stages partial nitritation - anammox (C-PN-A) process is an energy-efficient and sustainable technology for sludge anaerobic reject water treatment, which has usually reported with system instability and limited total nitrogen removal rate (TNRR). Overgrowth of flocculent heterotrophic bacteria in Anammox stage induced negative effects on anammox activity. To prevent direct transportation of flocculent heterotrophic bacteria from PN stage to Anammox stage, novel partial nitritation - microfiltration - anammox (PN-MF-A) process was proposed in this research. More stabilized operation was achieved for PN-MF-A process with higher TNRR of 0.80–0.96 kgN/(m3·d) than C-PN-A of 0.53–0.57 kgN/(m3·d). There was a great deal of overlaps in genus level of microbial community structure between floc sludge in PN and Anammox reactor, indicating flocculent microorganism in anammox reactor came from PN reactor, which probably could survive both in aerobic and anaerobic conditions. The in-between membrane of PN-MF-A process removed nearly 100% suspended solid (SS) and 15.31–37.83% COD, accordingly preventing the microorganism transfer from PN stage to Anammox stage and reducing the inhibitory effects of the anaerobic reject water on the anammox. Although same inoculum was used for the two sets anammox reactors, genus level shift was observed that Candidatus Brocadia (abundance 10%) in C-PN-A and Candidatus Kuenenia (1.4%) in PN-MF-A process. Higher anammox activity in PN-MF-A process was illustrated with less abundance (1.4%) than C-PN-A process. This research initially illustrated feasibility and advantages of proposed novel PN-MF-A process for high inhibitory reject water treatment. [Display omitted] • Novel partial nitritation - microfiltration - anammox (PN-MF-A) process was proposed. • More stabilized operation was achieved for PN-MF-A with higher TNRR of 0.80–0.96 kgN/(m3 d). • The in-between membrane removed nearly 100% suspended solid and 15.31–37.83% COD. • PN-MF-A prevented the microorganism transfer from PN stage to Anammox stage and reducing the inhibitory effects. • Although same inoculum was used, anammox genus level shift was observed. [ABSTRACT FROM AUTHOR]

Steam stripping and nitrification/denitrification for the elimination of nitrogen from sludge treatment reject water from the Central Sludge Treatment Facilities (CSTF) of the Emschergenossenschaft in Bottrop were tested in half-scale pilot plants. More than 90% efficiency could be achieved with both systems; the nitrification/dealtrification process also removed organic nitrogen. Operational experience has shown that full scale application of both systems is possible. The design surface load of the stripping column has been evaluated as 10 m³/(m²*h) and the steam/water ratio as 0.12 t/m³. The nitrification/denitrification process can be designed for 0.07 kgN/(kg MLSS*d) and 1.4 days hydraulic retention time. Total treatment costs are estimated to be between 5 and 7.5 DM/kg N. [ABSTRACT FROM AUTHOR]

Water after sludge dewatering, also known as reject water from anaerobic digestion, is recycled back to the main wastewater treatment inlet in the wastewater treatment plant Porsgrunn, Norway, causing periodic process disturbance due to high ammonium of 568 (±76.7) mg/L and total chemical oxygen demand (tCOD) of 2825 (±526) mg/L. The main aim of this study was the simultaneous treatment of reject water ammonium and COD using two pilot-scale sequential moving bed biofilm reactors (MBBR) implemented in the main wastewater treatment stream. The two pilot MBBRs each had a working volume of 67.4 L. The biofilm carriers used had a protected surface area of 650 m 2 /m 3 with a 60% filling ratio. The results indicate that the combined ammonia removal efficiency (ARE) in both reactors was 65.9%, while the nitrite accumulation rate (NAR) and nitrate production rate (NPR) were 80.2 and 19.8%, respectively. Over 28% of the reject water's tCOD was removed in both reactors. The heterotrophic nitrification and oxygen tolerant aerobic denitrification were the key biological mechanisms found for the ammonium removal in both reactors. The dominant bacterial family in both reactors was Alcaligenaceae , capable of simultaneous heterotrophic nitrification and denitrification. Moreover, microbial families that were found with equal potential for application of simultaneous heterotrophic nitrification and aerobic denitrification including Cloacamonaceae , Alcaligenaceae , Comamonadaceae , Microbacteriaceae , and Anaerolinaceae .

[Display omitted] • Nitrogen was bioelectroconcentrated from reject water in a 3-chamber set-up. • Nitrogen recovery was optimised based on nitrogen loading rate. • High nitrogen recovery efficiencies up to 75.5 ± 4.6% were obtained. • Energy needed for nitrogen recovery from real reject water was ≤8.2 ± 3.1 kWh kg N −1. • Enriched bioanode communities were dominated by phyla Bacteroidetes and Firmicutes. With the growing demand for macronutrients, such as nitrogen, and environmental issues related to their production, there is increasing need for efficient nutrient recycling. Reject waters from the dewatering of anaerobically digested sewage sludge are potential sources for nutrient recovery due to their high ammonium nitrogen (NH 4 -N) concentration (ca. 1 g NH4-N L−1) and low volume (ca. 1% of incoming sewage). In this study, a 3-chamber bioelectroconcentration cell was used for NH 4 -N recovery into a liquid concentrate from both synthetic and real reject water. NH 4 -N recovery efficiency and rate were optimised based on NH 4 -N loading rate, varying from 1.4 to 9.4 g NH4-N L−1 d−1 with synthetic reject water. The obtained NH 4 -N recovery efficiencies are the highest reported to date for bioelectroconcentration, peaking at 75.5 ± 4.6% (recovery rate of 728 ± 117 g N m−3 d−1) at loading rate 1.9 g NH4-N L−1 d−1. A loading rate of 2.9 g NH4-N L−1 d−1 led to the most optimal ratio between NH 4 -N recovery efficiency (68.2 ± 11.6%) and recovery rate (965 ± 66 g N m−3 d−1), with NH 4 -N up-concentrated 7.4 ± 0.9 times to 7483 ± 625 mg L−1 in the concentrate. With real reject water, NH 4 -N recovery efficiency of 53.2 ± 4.0% and recovery rate of 556 ± 37 g N m−3 d−1 were obtained at loading rate 2.5 g NH4-N L−1 d−1, with a specific energy consumption of 6.1 ± 1.1 kWh kg N −1. 16S rRNA amplicon analysis showed the dominance of phyla Bacteroidetes and Firmicutes in the anodic biofilms, with a significant change in the enriched microbial communities after transitioning from synthetic to real reject water. This study indicates the potential of bioelectroconcentration for nitrogen recovery from reject water without the need for an external organic carbon source or other chemical additions. [ABSTRACT FROM AUTHOR]

• SPNA system combined a novel ICCOMBR for reject water treatment was developed. • SPNA system could maintained stable operation under FA < 5.75 mg/L and FNA < 4 μg/L. • Nitrogen removal efficiency of SPNA system was 82%, with a NLR of 0.6 gN/L/d. • NO 2 −/NH 4 + ratio of 1.15 in PN was achieved by reducing AR from 1.65 to 0.8 L/min. • Anammox abundance in biofilm (22.2%) was equal to that in suspended sludge (20.77%). A novel internal circulation contact oxidation membrane bioreactor (ICCOMBR) was constructed to investigate a three steps startup strategy of single-stage partial nitritation-anammox (SPNA) system. A stable nitrite accumulation rate (NAR) of 86.60% was achieved with NH 4 +-N over 250 mg/L in nitritation process. The partial nitritation process could be effectively achieved by reducing the aeration rate (AR) by about 50% in the nitritation process, with an effluent NO 2 −-N/NH 4 +-N ratio of 1.15 ± 0.04. The SPNA system was started up in 27 days following the inoculated anammox granular sludge. A total nitrogen removal efficiencies of 82% was achieved at a NLR of 0.60 gN/L/d and dissolved oxygen (DO) concentration below 0.55 mg/L. Anammox function genus (Ca.Kuenenia and Ca. Anammoximicrobium) abundance accounted for 20.77% in the biofilm, which is approximately equal to 22.2% in the suspended sludge. Nitrosomon as the dominant AOB genera, was detected in the biofilm (6.5%) and suspended sludge (13.3%). [ABSTRACT FROM AUTHOR]

• Two-stage PN-anammox processes were efficient to treat reject water. • 53% COD was removed in PN process including oxygen-containing volatile organics, proteins and humic acids. • The effluent COD consisted mainly of recalcitrant hydrocarbons. • Organics in reject water stimulated the growth of denitrifying bacteria, Ottowia and Denitratisoma. Reject water contains complex components of organic compounds, which have significant influences on the nitrogen removal performance when treated using biological autotrophic nitrogen removal technology. In this study, a two-stage partial nitritation (PN)-anammox (floc-granule) system was established to treat reject water (COD/NH 4 +-N = 0.97 ± 0.15), and the evolution of organic compounds along PN and annamox bioreactors was investigated using gas chromatography–mass spectrometry and excitation-emission matrix. Also, the variation of PN and anammox sludge properties relating to COD reduction was examined. The PN-anammox system removed approximately 80% of total inorganic nitrogen and COD with hydraulic reaction time of 16 h. The influent organics (330–600 mg COD/L) in reject water were primarily composed of volatile, protein-like and humic acid-like organic compounds. PN process contributed 53 ± 18% of the overall COD removal, primarily including oxygen-containing organics (e.g. phenol), proteins and humic acids. Anammox process contributed 22 ± 15% of the overall COD removal, but large molecule acids (e.g. lactic acid) and small molecule alcohols (e.g. glycerol) were reoccurred, contributing to the effluent COD with recalcitrant hydrocarbons (e.g. n -Octadecane). Reject water increased the extracellular proteins/polysaccharides ratio of PN and anammox sludge, promoting the adsorption and degradation of organic compounds. High-throughput sequencing results showed that denitrifying bacteria of Ottowia increased from 0.03% to 14.4% in PN reactor, and of Denitratisoma increased from 9.6% to 15.4% in anammox reactor. The occurrence of these denitrifiers might mitigate the negative impact of organics to functional organisms. This study highlights the organics fate during PN-anammox treatment system, which is important to maintain the robust nitrogen removal when treating organics-containing and high ammonium concentration wastewater. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Technologies to remove nitrogen from wastewater are employed to preserve drinking water and prevent environmental damage. Nitrification/denitrification and partial nitrification-anammox are two accepted nitrogen removal techniques for wastewater treatment plants. These processes require energy for aeration and can release fugitive greenhouse gases in the form of nitrous oxide. Electrodialysis could potentially be used as an alternative to remove ammonium from waste streams, but previous experimentation has concluded that concentrate streams experience rapid scaling and fouling of membranes. This analysis compiles literature values to compare the state-of-the-art of municipal nitrogen removal to the new electrodialysis technique on an economic basis. Results show that nitrogen removal and recovery by electrodialysis is estimated to lower both initial capital costs and subsequent operation costs than traditional N removal technologies. Image 1 • Modeled electrodialysis ammonium recovery on municipal sludge digester reject water. • Developed optimization method based on stack cost and influent conditions. • Electrodialysis estimated to be less expensive than existing N removal technologies. • Cost differences come primarily from inexpensive and compact installation. [ABSTRACT FROM AUTHOR]

This study proposes a novel method to directly treat reject water with a high ammonium content, without relying on dilution. The originality of this method resides in leveraging the coordinated action of a methane- and methanol-dependent bacterial consortium and the biogas generated from wastewater treatment facilities. Specifically, ammonium is removed through autotrophic assimilation in the glutamate cycle of methanotrophs and Methylophilus while, simultaneously, methanol generated by methanotrophs is treated through formaldehyde assimilation as Methylophilus undergo the same ribulose monophosphate cycle as methanotrophs. Using this method, the backflow of high-concentration ammonium into the wastewater treatment process was reduced to 59% in a single operation using a sequencing batch reactor at a mean influent concentration of 877.3 mg L−1. However, the removal rate temporarily declined to an average of 37.6% at a concentration of 800 mg L−1 or above, which was imputed to the influence of toxic intermediates. Image 1 • A novel treatment method for reject water with high-concentration ammonium. • First nitrogen removal method using a CH 4 and CH 3 OH-dependent bacterial consortium. • Simultaneous methanol production and ammonia oxidation by methanotrophs. • Denitrification via RumP and glutamate cycles of methanotrophs and Methylophilus. [ABSTRACT FROM AUTHOR]

Water from anaerobic sludge dewatering (reject water that is recycled to the inlet main process treatment) from the Knarrdalstrand municipal wastewater treatment plant in Porsgrunn, Norway, contains 2.4 g/L of total chemical oxygen demand (TCOD) and 550 mg/L NH4-N (annual average). The high concentration of ammonium causes disturbances in the mainstream physical and chemical processes, while only a small fraction of the organics is biodegradable. A pilot-scale hybrid vertical anaerobic biofilm (HyVAB) reactor combining anaerobic and aerobic treatment was tested for reject water treatment to reduce process disturbances. The pilot HyVAB was prepared for the study with continuous aeration of the aerobic part of the reactor for 200 days, while two intermittent aeration schemes were applied during the three-month test period. Ammonium removal efficiency increased from 8% during the continuous aeration period to 50% at the end of the test when a short (7 min) aeration cycle was applied. COD removal was close to 20%, which was mainly obtained in the anaerobic stage and not significantly influenced by the aerations schemes. Simultaneous partial nitrification and denitrification were established in the biofilm that alternated between aerobic and anoxic conditions. The observed high ammonium removal is explained by two alternative shortcut processes via nitrite. The lack of biodegradable organics in the aerated stage suggests that most of the nitrogen removal was via the anammox pathway (autotrophic denitrification). The HyVAB, combining an anaerobic sludge bed and an intermittently aerated biofilm, appears to be an efficient process to treat high ammonium containing reject water. [ABSTRACT FROM AUTHOR]

The reject water from anaerobic digestion with high (Total Nitrogen) TN concentration was treated by a demonstration plant combining the anammox process and SOD (SOD®; Sulfur Oxidation Denitrification) process. The anaerobic digestion was a co-digestion of livestock wastewater, food waste water, and sewage sludge so that the TN concentration and conductivity of the reject water were very high. This anammox plant was the first anammox demonstration plant in South Korea. The maximum TN removal efficiency of 80% was achieved for the anammox reactor under nitrogen loading rate (NLR) of 0.45 kg-N/m3·d. As a result of decreasing the dilution of the reject water, the influent conductivity and NLR values were increased to 7.8 mS/cm and 0.7 kg/m3·d, causing a rapid decrease in the TN removal efficiency. The sludge concentration from the hydro-cyclone overflow was about 40 mg-MLVSS/L in which small sized anammox granules were detected. It was proven that the increase in (Mixed Liquor Volatile Suspended Solids) MLVSS concentration in the anammox reactor was not easy under high influent conductivity and NLR. 97% of NO2−-N+NO3−-N generated from the anammox process could be treated successfully by the SOD reactor. A TN removal efficiency of 35% under poor annamox treatment could increase to 67% by applying the SOD reactor post treatment for the removal of NO3−-N. The dominant anammox bacteria in the anammox reactor was identified as Brocadia fulgida and 9.3% (genus level) of the bacteria out of the total bacteria were anammox bacteria. [ABSTRACT FROM AUTHOR]