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Due to rapid industrialization and consequent heavy metal contamination in environment, there is an urgent need to develop cheap approaches for removal of harmful heavy metals. In this work, a simple cheap efficient paper-based technology has been developed for the removal of heavy metals from aqueous solution. For removal of heavy metals, for the first time one step green synthesis of chitosan carbon dots (CD) is reported here, via in-situ approach directly on paper using thermal assisted process. The functional paper with the embedded chitosan carbon dots (CD) has been characterized with UV–visible spectroscopy, Fourier-transformed infra-red spectroscopy (FT-IR), photoluminescence spectroscopy (PL), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The efficiency of the chitosan carbon dots paper (CDP) for the removal of heavy metals such as Cr, Sn and Hg were tested by immersing a carbon dot paper in a heavy metals solutions viz. Cr (0.1 mM), Sn (0.1 mM), and Hg (0.25 mM). It was observed that with this approach, we were able to effectively remove (80–100)% of these metals from solution and at the same time worked better than normal paper as well as normal chitosan coated paper. The mechanistic insight of adsorption is also discussed in the paper. Such paper-based separation system of heavy metals will lead to development of simple, facile, green and cost-effective separation system.

Anaerobic treatment of sedimented fibers collected from bottom of a bay that had been receiving pulp and paper mill wastewater for about 70 years were studied for the first time in semi-continuously fed continuously stirred tank reactors (CSTR). Anaerobic treatment of the fiber sediment was shown to be feasible, without dilution and with nitrogen and buffer supplement, at organic loading rates (OLR) up to 2.5 kg VS/m3d and hydraulic retention times (HRT) of 60 d resulting in methane yields of 201 ± 18 L CH4/kg VS. Co-digestion of sedimented fiber with sewage sludge at an OLR of 1.5 kg VS/m3d and HRT of 20 d resulted in a methane production of 246 ± 10 L CH4/kg VS. The techno-economic feasibility of mono and co-digestion process together with several case dependent factors such as maximum operable OLR, digestate utilization needs to be evaluated before making further conclusions for larger scale remediation applications. acceptedVersion

Contamination and associated risks posed by cadmium (Cd) and chromium (Cr) were characterized in the soils being continuously exposed by paper mill waste discharge in Assam, India. Soil samples from 20 (S-1 to S-20) sites surrounding a paper mill were analyzed by sequential extraction technique for Cd and Cr to assess the potential mobility and bioavailability of these heavy metals in the soils. Cadmium was mostly found in its carbonate fraction (37.14%) whereas; Cr was mostly available in Fe-Mn oxide bound fraction (34.72%). Relatively low amounts of Cd and Cr were associated with the water soluble fractions. The pollution load index (P i) values of Cd exceeded the maximum permissible limit i.e. 1 in all the sites but, for Cr it exceeded in all sites but S-7, S-13 and S-16. The mobility factor values ranged from 47.4% to 87.1% for Cd and 12.8–67.2% for Cr. High mobility factor values represent relatively higher biological availability in the soil samples and thus could pose environmental threats in the area surrounding the paper mill. The high values of other contamination factors, viz. individual and global contamination factors, potential ecological risk factor, ecological risk index and geo-accumulation index indicated that the studied area was widely polluted by Cd and Cr as a result of the effluents discharged from the paper mill.

This paper presents the first estimate of global water use in the forestry sector related to roundwood production for lumber, pulp, paper, fuel and firewood. For the period 1961–2010, we estimate forest evaporation at a high spatial resolution level and attribute total water consumption to various forest products, including ecosystem services. Global water consumption for roundwood production increased by 25% over 50 years to 961 × 109 m3/y (96% green; 4% blue) in 2001–2010. The water footprint per m3 of wood is significantly smaller in (sub)tropical forests compared to temperate/boreal forests, because (sub)tropical forests host relatively more value next to wood production in the form of other ecosystem services. In terms of economic water productivity and energy yield from bio-ethanol per unit of water, roundwood is rather comparable with major food, feed and energy crops. Recycling of wood products could effectively reduce the water footprint of the forestry sector, thereby leaving more water available for the generation of other ecosystem services. Intensification of wood production can only reduce the water footprint per unit of wood if the additional wood value per ha outweighs the loss of value of other ecosystem services, which is often not the case in (sub)tropical forests. The results of this study contribute to a more complete picture of the human appropriation of water, thus feeding the debate on water for food or feed versus energy and wood.

The pulp and paper industry wastewater treatment processes produce large volumes of biosludge. Limited anaerobic degradation of lignocellulose has hindered the utilization of biosludge, but the processing of biosludge using anaerobic digestion has recently regained interest. In this study, biosludge was used as a sole substrate in long-term (400 d) mesophilic laboratory reactor trials. Nine biosludge batches collected evenly over a period of one year from a pulp and paper industry wastewater treatment plant had different solid and nutrient (nitrogen, phosphorus, trace elements) characteristics. Nutrient characteristics may vary by a factor of 2-11, while biomethane potentials (BMPs) ranged from 89 to 102 NL CH4 kg(-1) VS between batches. The BMPs were enhanced by 39-88% with thermal pretreatments at 105-134 °C. Despite varying biosludge properties, stable operation was achieved in reactor trials with a hydraulic retention time (HRT) of 14 d. Hydrolysis was the process limiting step, ceasing gas production when the HRT was shortened to 10 days. However, digestion with an HRT of 10 days was feasible after thermal pretreatment of the biosludge (20 min at 121 °C) due to enhanced hydrolysis. The methane yield was 78 NL CH4 kg(-1) VS for untreated biosludge and was increased by 77% (138 NL CH4 kg(-1) VS) after pretreatment.

Pulp and paper mills generate large amounts of waste organic matter that may be converted to renewable energy in form of methane. The anaerobic treatment of mill wastewater is widely accepted however, usually only applied to few selected streams. Chemical oxygen demand (COD) removal rates in full-scale reactors range between 30 and 90%, and methane yields are 0.30-0.40 m(3) kg(-1) COD removed. Highest COD removal rates are achieved with condensate streams from chemical pulping (75-90%) and paper mill effluents (60-80%). Numerous laboratory and pilot-scale studies have shown that, contrary to common perception, most other mill effluents are also to some extent anaerobically treatable. Even for difficult-to-digest streams such as bleaching effluents COD removal rates range between 15 and 90%, depending on the extent of dilution prior to anaerobic treatment, and the applied experimental setting. Co-digestion of different streams containing diverse substrate can level out and diminish toxicity, and may lead to a more robust microbial community. Furthermore, the microbial population has the ability to become acclimated and adapted to adverse conditions. Stress situations such as toxic shock loads or temporary organic overloading may be tolerated by an adapted community, whereas they could lead to process disturbance with an un-adapted community. Therefore, anaerobic treatment of wastewater containing elevated levels of inhibitors or toxicants should be initiated by an acclimation/adaptation period that can last between a few weeks and several months. In order to gain more insight into the underlying processes of microbial acclimation/adaptation and co-digestion, future research should focus on the relationship between wastewater composition, reactor operation and microbial community dynamics. The potential for engineering and managing the microbial resource is still largely untapped. Unlike in wastewater treatment, anaerobic digestion of mill biosludge (waste activated sludge) and primary sludge is still in its infancy. Current research is mainly focused on developing efficient pretreatment methods that enable fast hydrolysis of complex organic matter, shorter sludge residence times and as a consequence, smaller sludge digesters. Previous experimental studies indicate that the anaerobic digestibility of non-pretreated biosludge from pulp and paper mills varies widely, with volatile solids (VS) removal rates of 21-55% and specific methane yields ranging between 40 and 200 mL g(-1) VS fed. Pretreatment can increase the digestibility to some extent, however in almost all reported cases, the specific methane yield of pretreated biosludge did not exceed 200 mL g(-1) VS fed. Increases in specific methane yield mostly range between 0 and 90% compared to non-pretreated biosludge, whereas larger improvements were usually achieved with more difficult-to-digest biosludge. Thermal treatment and microwave treatment are two of the more effective methods. The heat required for the elevated temperatures applied in both methods may be provided from surplus heat that is often available at pulp and paper mills. Given the large variability in specific methane yield of non-pretreated biosludge, future research should focus on the links between anaerobic digestibility and sludge properties. Research should also involve mill-derived primary sludge. Although biosludge has been the main target in previous studies, primary sludge often constitutes the bulk of mill-generated sludge, and co-digestion of a mixture between both types of sludge may become practical. The few laboratory studies that have included mill primary sludge indicate that, similar to biosludge, the digestibility can range widely. Long-term studies should be conducted to explore the potential of microbial adaptation to lignocellulosic material which can constitute more than half of the organic matter in pulp and paper mill sludge.

Pulp and paper wastewater (PPW) contains significant concentrations of phytosterols, suspected of inducing endocrine disruption in aquatic species. Aerated stabilization basins (ASBs) are commonly used for the treatment of PPW, but phytosterol removal varies among treatment systems. The objective of this study was to better understand the removal processes and biotransformation of phytosterols within an ASB treatment system fed with untreated PPW. PPW settled solids and supernatant fractions showed that phytosterols are primarily associated with settleable solids, which carry phytosterols to ASB sediment where anoxic/anaerobic conditions prevail. Bioassays with supernatant and settled PPW fractions of the raw wastewater conducted under aerobic and anaerobic conditions, respectively, showed that solids disintegration and hydrolysis results in phytosterol release in ASBs. A simulated ASB, fed with PPW and operated for 2.4 years at three hydraulic retention times (HRTs; 22.2, 11.1 and 5.6 d) with total phytosterol and solids loading rates from 10 to 42 μg/L-d and 44-178 mg/L-d, respectively, was used to determine the steady-state effluent quality and sediment characteristics. Although effluent COD and phytosterol concentrations were relatively low and stable (84-88% total COD removal; 82-94% total phytosterol removal) across the range of HRTs tested, sediment COD and phytosterol concentrations increased with increasing loading rate. On average, 51% of the phytosterols entering the ASB were removed via biotransformation, 40% were retained in the sediment, and the remaining 9% exited with the effluent. This study demonstrates the role of sediment as a source of phytosterol release in ASBs and highlights the importance of HRT and the PPW characteristics for predicting phytosterol fate in ASBs.

Capacitive deionization (CDI) has emerged as an attractive approach for desalination and water treatment for its high energy efficiency, low cost, and easy regeneration. Here, we report the preparation and application of villiform carbon fiber paper (v-CFP) as the current collector for CDI device with high areal electrosorption capacity. The v-CFP was prepared by thermal annealing and subsequent O2 plasma etching of the commercial pristine carbon fiber paper (p-CFP). With greatly improved surface area and hydrophilicity, the v-CFP itself showed an areal capacitance as high as 0.70 F·cm−2 in 0.5 M NaCl solution, and delivered an areal electrosorption capacity up to 122 and 400 mg·m−2 when feeding a NaCl solution with initial concentration of 50 and 3500 mg·L−1, respectively. Upon loading with additional electrode materials (EMs), e.g., graphene hydrogel, activated carbon, carbon nanotubes, and porous carbon spheres, the v-CFP/EM electrodes exhibited further improved areal electrosorption capacities, generally outperforming the corresponding p-CFP/EM electrodes by >2 times. Our studies demonstrate that proper surface treatment can largely improve the capacitance of the commonly used p-CFP current collector, making it greatly attractive in CDI devices.

There have been limited studies on the potential use of enzymes for enhancing the dewaterability of biosludge. The mechanisms for such enhancement have not been investigated despite the environmental advantages of using enzymes over synthetic polymers for biosludge conditioning. In order to find enzymes with this potential, a screening of commercially available enzymes was carried out using capillary suction time to assess biosludge dewaterability. The only enzyme that showed dewatering improvements in the screening tests was a lysozyme which reduced the capillary suction time by 36% and increased the cake solids content from 5.6 to 8.9 DS%. Lysozyme aided in the flocculation of particles reducing the polymer demand from 11% to 6%. Active and inactive lysozyme exhibited a similar ability for enhancing sludge dewatering, indicating that the conditioning mechanism of lysozyme is similar to that of a flocculant.

As a cost-effective alternative to silver nanoparticles, we have investigated the use of copper nanoparticles in paper filters for point-of-use water purification. This work reports an environmentally benign method for the direct in situ preparation of copper nanoparticles (CuNPs) in paper by reducing sorbed copper ions with ascorbic acid. Copper nanoparticles were quickly formed in less than 10 minutes and were well distributed on the paper fiber surfaces. Paper sheets were characterized by x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectroscopy, and atomic absorption spectroscopy. Antibacterial activity of the CuNP sheets was assessed for by passing Escherichia coli bacteria suspensions through the papers. The effluent was analyzed for viable bacteria and copper release. The CuNP papers with higher copper content showed a high bacteria reduction of log 8.8 for E. coli. The paper sheets containing copper nanoparticles were effective in inactivating the test bacteria as they passed through the paper. The copper levels released in the effluent water were below the recommended limit for copper in drinking water (1 ppm).

Recently, new technologies regarding water and wastewater treatment have been developed and among these processes, the fixed bed biofilm reactor combined with membrane bioreactor is the recent alternative solution to conventional technologies. In this research, an integrated fixed bed membrane bioreactor (FBMBR) with a hydraulic retention time (HRT) of 36 h was developed to remove pollutants from real paper-recycling wastewater. The removal efficiencies of chemical oxygen demand (COD), ammonium, nitrite, nitrate and total nitrogen (TN) for permeate and supernatant were in the range of 92–99%, 59–97%, 78–97%, 59–98% and 68–92%, respectively. In addition, the membrane fouling was evaluated by transmembrane pressure (TMP) monitoring during experimental period at a constant flux of 12 l m−2.h−1, and the TMP increasing rate was 2 mbar/day. The results as a whole indicated that the FBMBR can be applied effectively to removal of pollutants from real paper-recycling wastewater. Keywords: Fixed bed membrane bioreactor (FBMBR), Membrane fouling, Transmembrane pressure (TMP)

The preparation of nanocrystalline cellulose from waste printed papers as adsorbent was conducted using organic solvent. The synthesize of nanocrystalline cellulose is characterized by Fourier transform-infra red (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Hydroxynaphtol blue and congo red in aqueous solutions are used as sorbate in this study to test the single system adsorption capacity of nanocrystalline cellulose using Langmuir and Freundlich isotherm models at 30, 40, and 50 °C. Kinetic study are quantified using pseudo-first order and pesudo-second order models. The adsorption of both azo dyes resulted in negative value of ΔG° which shows spontaneous adsorption of both azo dyes onto adsorbent active sites. Higher temperature increase the adsorption of dyes represents the endothermic nature of adsorption and randomness of adsorbent-solution interface.

Transformation plays a significant role in solving hydrological problems. In response to the comment on Singh and Das (2015) by Deng et al. (2015) regarding the transformation, boundary conditions and subsequent analytical solution of advection dispersion equation in semi-infinite heterogeneous porous media, it is argued that the transformation used by Singh and Das (2015) for finding the analytical solution is correct and mathematically valid. Also, the different expression of f ( mt ) used to obtain the solution are explained with their physical relevance in the field.

Capacitive deionization (CDI) based on the principle of electrochemical double layers has emerged as a prospective water treatment technology to challenge the water scarcity. Herein, a novel integrated CDI electrode comprised of large-scale and vertically aligned Co(OH)2 nanosheets on the GP matrix (Co(OH)2@GP) has been prepared successfully via a facile hydrothermal strategy for the first time. The texture analyses such as TEM, SEM, XPS, XRD and N2 adsorption indicated that well-grown and interconnected Co(OH)2 nanosheets on the GP matrix ensured the electrode a high specific surface area (207.62 m2/g) and superior open pore network. The electrochemical performance investigated by the CV, EIS and GC techniques revealed that the Co(OH)2@GP electrode combing the merits of Co(OH)2 nanomaterial and GP efficiently obtained the amazing specific capacitance of 411.02 F/g, good electric conductivity and favourable cyclability. Moreover, the CDI behaviour of Co(OH)2@GP electrode evaluated by the batch mode experiments in the 300 mg/L of NaCl solution demonstrated an ultrahigh salt removal capacity of 48.21 mg/g and excellent regeneration ability. The highly simplified electrode processing, free binder and outstanding CDI performance render the Co(OH)2@GP electrode a promising candidate in the highly efficient CDI application.

Hereby, two mistakes of writing and applying pseudo-first order kinetic and Brunauer-Emmett-Teller (BET) isotherm models for adsorption systems have been pointed out. In this discussion, it is recommended and suggested to cite any kind of model e.g. kinetic, thermodynamic, isotherm, and so on from original papers of the mentioned models as well as a careful writing in order to prevent from repeating such inadvertent mistakes to publish more valuable and readable papers.

The present quasi-experimental research investigated the growth ability and removal efficiency of Hydrilla verticillata in freshwater from Nong Han Lake (NHL), domestic wastewater from constructed wetlands (CW) and wastewater from university canteen wastewater (UCW) in Sakon Nakhon, a north-east province in Thailand. The growth rate was measured by evaluating the fresh mass of H. verticillata and comparing the removal efficiency of the biochemical oxygen demand (BOD), the chemical oxygen demand (COD) and phosphate at the hydraulic retention time on days 7, 14, 21 and 28. The efficiency of BOD removal of H. verticillata in UCW, NHL and CW was 26, 80 and 84%, respectively, whereas the COD removal efficiency was 25, 72 and 63%, respectively, and that of phosphate was 6, 44 and 87%, respectively. No difference was found in growth rates between H. verticillata from NHL and CW. Further, CW provided a good growth rate of H. verticillata, and the domestic wastewater discharges could provide a rapid growth of H. verticillata. Finally, H. verticillata might be used in aquatic ecosystems.

The presence of antibiotic resistant bacteria in municipal wastewater treatment plants represents a real risk to human health. For the first time, this paper shows that the inactivation rate of cefotaxime resistant bacteria is the same as total bacteria when secondary effluents are treated by the solar photo-Fenton process. To obtain this result, an exhaustive and comparative kinetic study on the inactivation of both total and cefotaxime resistant bacteria (Total coliform, Escherichia coli and Enterococcus sp) was carried out, taking into account the effects of the main operation conditions, such as solar irradiance and iron concentration, and operation mode (batch and continuous). In all the operation conditions studied, no significant differences were found between the first order inactivation rate constants, ki, of total and cefotaxime resistant bacteria. Additionally, ki increased with solar irradiance and iron concentration. As for the effect of the operation mode, the main finding of this work is much quicker inactivation in continuous flow mode than in batch mode, pointing out its potential application at large scale. The best continuous operation condition to inactivate the bacteria to the detection limit (1 CFU mL−1), was at 22.4 min of hydraulic residence time with 5 mg Fe2+ L−1 and 30 mg H2O2·L−1. This treatment time is approximately a third of that reported in batch mode. The efficiency, in terms of figure of merits, of the continuous flow operation was 2.7 m2 of solar collector area to reduce one log of E. coli concentration per m3 of treated water and per hour, in comparison with 2137 m2 calculated for batch operation under the same solar UVA irradiance, 30 W m−2. This paper encourages research into continuous solar disinfection processes due to its enhanced efficiency with regard to the commonly used batch wise operation and shows that efficient removal of total bacteria ensures the removal of antibiotic resistant bacteria.

Mixotrophic denitrification processes have a great potential in nitrogen removal in biological wastewater treatment processes. However, so far, few studies have focused on the mixotrophic denitrification system using Fe(II) as an exclusively assisted electron donors and the underlying mechanisms in such a process remain unclear. Furthermore, the mechanisms by which microorganisms cover carbon, nitrogen, phosphorus and iron in an iron-assisted mixotrophic system remain unrevealed. In this work, we explore the feasibility of using Fe(II) as an assisted electron donor for enhancing simultaneous nitrogen and phosphorus removal via long-term reactor operation and batch tests. The results show that Fe(II) could provide electrons for efficient nitrate reduction and that biological reactions played a predominant role in these systems. In these systems Thermomonas, a strain of nitrate-reduction Fe(II)-oxidation bacterium, was enriched and accounted for a maximum abundance of 60.2%. These findings indicate a great potential of the Fe(II)-assisted mixotrophic denitrification system for practical use as an efficient simultaneous nitrogen and phosphorus removal process.

Up-flow anaerobic sludge blanket (UASB) processes treating purified terephthalic acid (PTA) wastewater often face challenges associated with biomass loss. As excessive biomass loss could lead to deterioration of PTA removal, biostimulation and bioaugmentation were often practiced without understanding the microbial impact in UASB. Three laboratory-scale UASB reactors were operated with synthetic PTA wastewater as the feed, with two added with co-substrate (glucose or molasses) on Day 170 for 90 days, and one with external granules on Day 118. Throughout the operation, treatment performance was measured together with the analysis of microbial communities of biomass samples using 16S rRNA-based gene Illumina sequencing. Glucose amendment destabilized both terephthalic acid and para-toluic acid removal, while molasses amendment improved para-toluic acid removal. Both substrate addition generally led to decreases in the abundances of syntrophs and methanogens and increases in carbohydrate-fermenting bacteria in the granular sludge. Regarding bioaugmentation, paper mill granule addition led to a temporary crash of terephthalic acid removal for 42 days, and deterioration of para-toluic acid removal throughout the operation. Syntrophs and methanogens were observed to colonize on the paper mill granules after three months, meanwhile growth of methanogens were stimulated on the PTA granules added initially. Overall, proper level of molasses amendment and external granule inoculation could be promising strategies to make up for biomass loss during the operation of PTA-degrading UASB.

Secondary disinfectants, such as chlorine and chloramine, have been widely applied to minimise microbial risks in drinking water during distribution. Key challenges have included the maintenance of stable concentrations of disinfectant residuals and the control of disinfection by-products that may form as a consequence of residual decay processes. Many factors may influence disinfectant residual stability and the consequential formation of by-products. Thus predictions of disinfectant stability and by-product formation are multifactorial problems, complete with numerous complications of parameter co-dependence and feedback amplification of some key parameters. The aim of this review was to derive an understanding of how disinfectant residual stability in drinking water distribution systems is impacted by various influencing factors such as water quality and operational parameters. Factors known to influence disinfectant stability and by-product formation were critically reviewed. A systematic review method was applied to identify 1809 journal articles published in the two decades from January 1998 to December 2017. From the initial screening, 161 papers were selected for detailed assessment. Important factors were identified to include temperature, water age, piping material, corrosion products, pH, hydraulic condition, disinfectant residual type and dosage and microbial activity. Microbial activity is a particularly complex parameter on which to base predictions since many factors are known to influence the degree and nature of such activity. These include temperature, water age, piping material, corrosion products, nutrients, natural organic matter, hydraulic condition and disinfectant residual type and dosage. Disinfectant types and dosages were found to be among the most important factors. Many knowledge gaps and research needs still remain, including the need for a more complete understanding of the factors that influence the production of nitrogenous disinfection by-products.

Fouling in membrane filtration processes is problematic. Causes are often specific depending on feed water constituents, the membrane and the chemical products used. Some fouling will badly affect membrane performance and cleaning will therefore be necessary. Cleaning can be supported by antiscalant treatments to reduce the risk of membrane fouling. However, some antiscalants may also lead to fouling. This paper presents the major problems of reverse osmosis plant in Jerba Island, namely the influence of antiscalant type on the water characteristics and membrane fouling. This was related to the increase of pressure drop, permeate conductivity and cleaning frequency. To identify the causes of membrane fouling, different investigations were carried out. Membrane autopsy, chemical analysis of feed water, follow-up of the operation parameters. The objective of membrane autopsy, by means of SEM/EDS, was to carry out a destructive analysis on a fouled membrane in order to identify the major causes of fouling. The results show that the film was composed mostly of organic matter, with significant presence of nitrogen, iron and silicates. These findings demonstrate how the antiscalants altered the water characteristics. Thus, the selection of the type of antiscalant should take into account the associated contribution to membrane fouling development.

This paper suggests a bio-inspired system that simultaneously addresses water and food shortages. In this system, saline water is desalinated using forward osmosis (FO) process to deliver fresh water to a hydroponic culture, without the need for recovery of draw agent. Inspiring from in-vivo blood vessel functionality within biological tissues, ultrafiltration hollow fiber membranes (HF) were exploited to deliver nutrients to plants without compromising FO driving force. A copolymer of N‑isopropylacrylamide and sodium acrylate hydrogel particles were used as both draw solution and hydroponic culture. As a proof of concept, cress and basil seeds were used as the model plant in the hydroponic culture. Although the low water flux of FO desalination process is known as its major drawback, here we take advantage of this low flux to design a new sustainable system to produce fresh water and grow plants. It was observed that the addition of seeds regardless of their type increases the water flux higher than that of hydrogel only. Also, the release of hydroponic nutrient from HFs is essential for the system to function. The parallel configuration of hollow fiber membranes with seeds placed adjacent to the fibers exhibited the best growth pattern.

© 2021 Elsevier B.V. Minimal liquid discharge (MLD) in greenhouses minimizes the volume of discharged wastewater, thereby increasing the volume of effluent that may be reused. Sodium accumulation in wastewater is often considered the main bottleneck to achieving 100% reuse. Consequently, greenhouses have begun adopting reverse osmosis (RO), the most commonly used desalination technology for wastewater treatment. RO removes ions from wastewater indiscriminately, including multivalent nutrients to crops (Ca[superscript 2+], Mg[superscript 2+], SO[subscript 4][superscript 2−], PO[subscript 4][superscript 3−]). In contrast, monovalent selective electrodialysis (MSED) selectively removes monovalent sodium while retaining multivalent nutrients in solution. For greenhouses that have not achieved MLD, MSED has an alternative application of reducing levels of nitrate, a monovalent ion and agricultural pollutant, in wastewater for disposal. This paper investigates the monovalent selectivity and potential of the widely-used Neosepta MSED membranes and the new Fujifilm MSED membranes to treat wastewater in greenhouses for reuse or discharge. Eight effluent compositions are tested as feedwater in a laboratory MSED system. Both membranes demonstrate selectivity towards sodium and nitrate across the tested compositions. Fujifilm cation-exchange membranes remove two to six sodium ions, compared to Neosepta's two to eight, for every magnesium ion. Fujifilm anion-exchange membranes remove two to seven nitrate ions, compared to Neosepta's two to six, for every sulfate ion.

Process optimization is a popular strategy to improve efficiency, reduce the energy consumption and total cost of the seawater reverse osmosis (SWRO). Forward osmosis (FO) process with a nanofiltration (NF)-like membrane has emerged as a cost-effective technology for seawater desalination pretreatment, due to its high water permeability and low energy consumption compared to RO-like FO membrane. The present work comprehensively evaluated the potential of using an NF-like FO membrane for SWRO pretreatment and analyzed the feasibility of the NF-like membrane-based FO-NF-RO process for seawater desalination. The performance of the FO-NF-RO integrated process was investigated with MgSO4, Na2SO4, and Mg(CH3COO)2 as draw solute, respectively. Besides, the energy consumption and total cost of the hybrid process were also estimated on the laboratory and large scale. The NF-like membrane-based FO process could effectively remove organic molecules and divalent ions effectively. The hybrid process product water could reach the drinking water standard in China (TDS ≤ 1000 mg/L). When water recovery was 42.0%, the hybrid process could produce freshwater with specific energy consumption of 2.99 kWh/m3 and specific water cost of 0.92 $/m3, which were comparable with the conventional SWRO process. Overall, our study revealed the feasibility of the FO-NF-RO process for seawater desalination.

Intermittent water supplies (IWS) are routinely experienced by drinking water distribution systems around the world, either due to ongoing operational practices or due to one off interruptions. During IWS events changing conditions may impact the endemic biofilms leading to hydraulic mobilisation of organic and inorganic materials attached to pipes walls with a resulting degradation in water quality. To study the impact of IWS on the microbiological and physico-chemical characteristics of drinking water, an experimental full-scale chlorinated pipe facility was operated over 60 days under realistic hydraulic conditions to allow for biofilm growth and to investigate flow resumption behaviour post-IWS events of 6, 48 and 144 hours.\ud \ud \ud \ud Turbidity and metal concentrations showed significant responses to flow restarting, indicating biofilm changes, with events greater than 6 hours generating more turbidity responses and hence discolouration risk. The increase in pressure when the system was restarted showed a substantial increase in total cell counts, while the subsequent increases in flow led to elevated turbidity and metals concentrations. SUVA254 monitoring indicated that shorter times of non-water supply increased the risk of aromatic organic compounds and hence risk of disinfection-by-products formation. DNA sequencing indicated that increasing IWS times resulted in increased relative abundance of potential pathogenic microorganisms, such as Mycobacterium, Sphingomonas, and the fungi Penicillium and Cladosporium.\ud \ud \ud \ud Overall findings indicate that shorter IWS result in a higher proportion of aromatic organic compounds, which can potentially react with chlorine and increase risk of disinfection-by-products formation. However, by minimising IWS times, biofilm-associated impacts can be reduced, yet these are complex ecosystems and much remains to be understood about how microbial interactions can be managed to best ensure continued water safe supply.

Soil contamination, due to the leakage of petroleum or its by-products, is a reason for concern nowadays. Technologies, such as bioremediation, have been developed to remove these pollutants from the environment. This paper aims to evaluate the bioremediation of clayey acid soils contaminated with diesel oil, comparing the effect of aeration use and the addition of different sawdust ratios (5% and 10%) as bulking material. This research was developed in three phases, with experiments of (a) natural attenuation (exclusively natural processes), (b) sawdust-amended soil and (c) aeration combined with sawdust addition. The manometric respirometry test was applied to monitor CO2 production during biodegradation experiments and sodium hydroxide (NaOH) was used as an absorbent solution. The contamination of the samples was carried out by the addition of diesel oil (5% w/w (gg−1)) into the soil. The results indicated that natural attenuation presented a slower bioremediation process when compared to the treatments with sawdust addition. The addition of 5% of sawdust was beneficial to the microbial activity of the soil, but a proportion above 5% caused a negative effect on the samples, reducing the microbial activity. Statistical analysis (Kruskal-Wallis test) showed significant oil removals on experiments with the combination of sawdust and aeration. The aeration was considered the main agent in increasing oil biodegradation in the soil. The degradation rate reactions followed a zero-order linear model. The highest contaminant degradation rate was observed in the samples with 5% of sawdust and aeration (24.79 mgO2 kg−1dry soil day−1), which also improved microbial activity and diesel oil removal. Keywords: Bioremediation, Diesel oil, Contaminated soil, Sawdust, Aeration

In cold areas, nitrogen removal performance of wastewater treatment plants (WWTP) declines greatly in winter. This paper systematically describes the enhancement effect of a periodic reverse electrocoagulation technology on biological nitrogen removal at low temperatures. The study showed that in the lab-scale systems, the electrocoagulation technology improved the biomass amount, enzyme activity and the amount of nitrogen removal bacteria (Nitrosomonas, Nitrobacter, Paracoccus, Thauera and Enterobacter). This enhanced nitrification and denitrification of activated sludge at low temperatures. In the pilot-scale systems, the electrocoagulation technology increased the relative abundance of cold-adapted microorganisms (Luteimonas and Trueperaceae) at low temperatures. In a full-scale industrial WWTP, comparison of data from winter 2015 and winter 2016 showed that effluent chemical oxygen demand (COD), NH4+-N, and NO3−-N reduced by 10.37, 3.84, and 136.43 t, respectively, throughout the winter, after installation of electrocoagulation devices. These results suggest that the electrocoagulation technology is able to improve the performance of activated sludge under low-temperature conditions. This technology provides a new way for upgrading of the performance of WWTPs in cold areas.

The paper analyses the extrapolation of the results obtained in a pilot plant to a full-scale seawater desalination plant. A technological system was implemented in the pre-treatment line of Las Palmas III seawater reverse osmosis (RO) desalination plant with a capacity of 36,000 m3/d. This system is aimed to control membrane fouling. It consists in the non-dosing of sodium hypochlorite or another biocide to seawater in order to minimize RO membrane biofouling. The pH regulation at 6.5 controls the scaling and the 12.5 ppm dosage of FeCl3 as a coagulant maximizes the coagulation efficiency of colloidal particles and controls the fouling process.

Cellulose from used toilet paper is a major untapped resource embedded in municipal wastewater which recovery and valorization to valuable products can be optimized. Cellulosic primary sludge (CPS) can be separated by upstream dynamic sieving and anaerobically digested to recover methane as much as 4.02 m3/capita·year. On the other hand, optimal acidogenic fermenting conditions of CPS allows the production of targeted short-chain fatty acids (SCFAs) as much as 2.92 kg COD/capita·year. Here propionate content can be more than 30% and can optimize the enhanced biological phosphorus removal (EBPR) processes or the higher valuable co-polymer of polyhydroxyalkanoates (PHAs). In this work, first a full set of batch assays were used at three different temperatures (37, 55 and 70 °C) and three different initial pH (8, 9 and 10) to identify the best conditions for optimizing both the total SCFAs and propionate content from CPS fermentation. Then, the optimal conditions were applied in long term to a Sequencing Batch Fermentation Reactor where the highest propionate production (100–120 mg COD/g TVSfed·d) was obtained at 37 °C and adjusting the feeding pH at 8. This was attributed to the higher hydrolysis efficiency of the cellulosic materials (up to 44%), which increased the selective growth of Propionibacterium acidopropionici in the fermentation broth up to 34%. At the same time, around 88% of the phosphorus released during the acidogenic fermentation was recovered as much as 0.15 kg of struvite per capita·year. Finally, the potential market value was preliminary estimated for the recovered materials that can triple over the conventional scenario of biogas recovery in existing municipal wastewater treatment plants.

During algal bloom, it's a challenge to provide good quality feed water, and ensure sustainable RO plant operations without an adequate pre-treatment of seawater. In this paper, the effectiveness of the coagulation process with the individual and dual coagulants, using alum, FeCl3 and chitosan, were explored aiming to remove microalgae from seawater. The coagulation-flocculation-sedimentation (C-F-S) experiments were conducted by optimizing multiple process strategies to reduce the amounts of coagulants and also to shorten the sedimentation process time. The coagulation-flocculation-dissolved air flotation (C-F-D) experiments were performed to generate the process data in order to evaluate the dual coagulation process performance of the C-F-S system. C-F-S experiments using FeCl3 coagulant gave better process performance (20 ppm FeCl3 dose, 8.2 pH, 30 min sedimentation time and 98% microalgae removal efficiency) when compared to alum and chitosan based individual coagulations. The process time of the coagulation process was significantly reduced by the addition of chitosan as a flocculent aid. For dual coagulation using alum (10 ppm) as coagulant and chitosan (1 ppm) as flocculent aid improved microalgae removal efficiency to 98% at a reduced process time of 5 min, making C-F-S process as attractive as C-F-D process.

Since the 1980s, the pulp and paper industry in Finland has resulted in the accumulation of fibres in lake sediments. One such site in Lake Näsijärvi contains approximately 1.5 million m3 sedimented fibres. In this study, the methane production potential of the sedimented fibres (on average 13% total solids (TS)) was determined in batch assays. Furthermore, the methane production from solid (on average 20% TS) and liquid fractions of sedimented fibres after solid-liquid separation was studied. The sedimented fibres resulted in fast methane production and high methane yields of 250 ± 80 L CH4/kg volatile solids (VS). The main part (ca. 90%) of the methane potential was obtained from the solid fraction of the sedimented fibres. In addition, the VS removal from the total and solid sedimented fibres was high, 61–65% and 63–78%, respectively. The liquid fraction also contained a large amount of organics (on average 8.8 g COD/L), treatment of which also has to be considered. The estimations of the methane production potentials in the case area showed potential up to 40 million m3 of methane from sedimented fibres. acceptedVersion

One of the serious problems found in desalination using reverse osmosis (RO) is concentrate or brine management. This concentrate can actually be used as a raw material for salt production. However, antiscalants added during RO process should be removed before salt crystallization. This paper presents the separation of antiscalants from RO concentrate solution using nanofiltration (NF) membrane. Sodium hexametaphosphate (SHMP) and disodium ethylenediaminetetraacetate (Na2EDTA) were used as models of antiscalants. The effect of antiscalants concentration and addition of natural organic matters on both flux behavior and rejection were investigated. The results showed that the permeate flux behavior was influenced by the sodium chloride solution itself as a solution background, antiscalant type and antiscalant concentration. Osmotic pressure, concentration polarization and fouling or scaling contributed to flux decline during nanofiltration of antiscalants. NF membrane demonstrated very high rejection for both SHMP and Na2EDTA.

Capsid integrity quantitative PCR (qPCR), a molecular detection method for infectious viruses combining azo dye pretreatment with qPCR, has been widely used in recent years; however, variations in pretreatment conditions for various virus types can limit the efficacy of specific protocols. By identifying and critically synthesizing forty-one recent peer-reviewed studies employing capsid integrity qPCR for viruses in the last decade (2009–2019) in the fields of food safety and environmental virology, we aimed to establish recommendations for the detection of infectious viruses. Intercalating dyes are effective measures of viability in PCR assays provided the viral capsid is damaged; viruses that have been inactivated by other causes, such as loss of attachment or genomic damage, are less well detected using this approach. Although optimizing specific protocols for each virus is recommended, we identify a framework for general assay conditions. These include concentrations of ethidium monoazide, propidium monoazide or its derivates between 10 and 200 μM; incubation on ice or at room temperature (20 - 25 °C) for 5–120 min; and dye activation using LED or high light (500–800 Watts) exposure for periods ranging from 5 to 20 min. These simple steps can benefit the investigation of infectious virus transmission in routine (water) monitoring settings and during viral outbreaks such as the current COVID-19 pandemic or endemic diseases like dengue fever., Graphical abstract Image 1, Highlights • PMA/PMAxx have higher efficiency removing false negatives from qPCR for DNA/RNA viruses than EMA. • One size fits all pretreatment approaches are possible but lead to lower virus signal reduction. • Capsid integrity qPCR is a valuable tool to adapt existent workflows for improving risk assessment. • Azo dye pretreatment can help refine significance of qPCR during virus outbreaks.

In this paper, the performance and effectiveness of combined sequencing batch reactor (SBR) and reverse osmosis (RO), as well as differences in treating young and matured landfill leachate, was investigated. Samples of young and stabilized leachate were collected from a municipal landfill in north-eastern Poland. The general pollution parameters, organic and inorganic indicators were determined in raw leachate and after each step of leachate treatment. The performance characteristics of the reverse osmosis system were made based on permeate flux, electroconductivity removal rate, concentration factor and removal rate. The use of biological pre-treatment had a good efficiency (>98% for both leachate) in ammonia nitrogen removal. The SBR treatment effectiveness for BOD (64%), Fe (29%), Cl− (0.2%) and Total Organic Carbon (-5.3%) was lower for young leachate compared to a stabilized. Pretreated leachate was directed to a RO system which was characterized by better operational parameters during the filtration of stabilized leachate: the average permeate flux was higher by 3.3 L/m2⋅s⋅10−6 and the filtration time was shorter by 110 min compared to the young leachate. The main reason of membrane clogging during young leachate filtration was a higher content of organic matter and its neutralization by Ca2+ and N-NH4+ presented in leachate, causing clogging of negatively charged RO membrane. Another reason could be complex formation between iron and natural organic matter that may precipitate on the membrane surface or inside the pores. This study has shown a high removal efficiency (over 80%) of the integrated SBR-RO method for all analyzed parameters.

Seawater desalination has two major negative environmental impacts: brine production/discharge and a large carbon footprint arising from energy consumption. Sequential CO2 mineralization is a promising technology to address both issues. This paper reports the effects of key reaction parameters in this process, namely additional agitation of the reactant phases, presence of electrolytes, and CO2 microbubble injection rate. It was found that enhanced mass transport of reactants under agitation and an appropriate CO2 microbubble injection rate are necessary for effective CO2 mineralization by precipitating carbonate minerals. Compared to deionized water, various electrolytes in the brine reduced the amount of CO2 required to achieve the same Mg conversion ratio. However, deionized water led to a much higher purity (98%) of the precipitated hydromagnesite, a valuable product of sequential CO2 mineralization. This report provides useful guidelines for the design of systems for sequential CO2 mineralization with seawater desalination brine.

Biological activated carbon (BAC) filters can be used to remove residual total organic carbon (TOC) from greywater after a membrane bioreactor. The two main TOC removal processes are adsorption to the granular activated carbon (GAC) and biological degradation. Biodegradation leads to the growth of microorganisms in the filter bed, which can lead to increased pressure loss over the filter bed. However, the roles of sorption and biodegradation in long-term TOC removal and how they complement each other are unclear. We monitored TOC removal from greywater in a BAC filter installed following a membrane bioreactor over more than 900 days. Removal performance depended on the operational time of the BAC filter, the influent TOC concentration, and in the upper part of the filter on the empty bed contact time (EBCT). Across the overall filter, the EBCT did not significantly influence TOC removal, showing that the filter was sufficiently large for the range of flow rates observed. Analysis of the long-term data revealed the equal importance of sorption and biodegradation over the whole operation period and the whole filter bed. Most of the TOC was removed in the upper part of the filter, where biodegradation was the dominant mechanism. In the lower part of the filter, sorption capacity remained and allowed high influent TOC concentrations to be buffered. The generous filter design with low average filtration rates ensured long-term TOC removal. The only maintenance needed was backwashing, which was required only after more than 800 days of operation. Backwashing effectively reduced the pressure loss but had no significant influence on the effluent water quality. Our study shows that BAC filters are a suitable post-treatment step for the treatment of greywater with highly variable flow and TOC concentrations., Water Research X, 13, ISSN:2589-9147

The textile industry causes massive water pollution. As far as the color of textile wastewater is the most visible source of this pollution, it is the most studied. However, could the color of textile wastewater be only the top of the issue? Could the problem be recognized as an iceberg effect? Why is color removal not comparable to mineralization? This review paper tries to summarize the recent experience in the field of enhanced textile wastewater treatment. The enhancement through catalytic action for dye removals and their by-products was widely discussed. The basis of catalytic effects was studied for ozone-, H2O2, electro-, photo- and plasma-based processes. The synergistic effects in hybrid AOPs were discussed. The authors’ ambition was to highlight the by-products accumulation problem and emphasize the need for more advanced textile wastewater treatment, hoping to avoid the occurrence of a new group of dye-sourced micropollutants in the environment.

The evaluation of fouling behavior, including biofouling, is crucial to increase efficiency in the reverse osmosis (RO) seawater desalination process (SDP). This paper reports on biofouling behavior in seawater in the SDP, detected by monitoring intracellular, extracellular, and total adenosine triphosphates (ATPs) in the cross-flow RO filtration system as bacterial activity tracers. The first-stage ultrafiltration (UF) treatment of raw seawater reduced the ATP range to approximately 25%, while the ATP concentration in seawater did not decrease significantly on average between the subsequent four stages until the RO membrane treatment. The results demonstrated temporal variation of ∆ATPs, the deference in ATPs between in RO concentrated water and in RO feed water, occurs randomly, as the membrane fouling index, evaluated from pressure measurements, increases to the level of fouling that requires cleaning. The significant increase in ∆ATPs despite a residence time of only approximately fifteen seconds over the RO module reflects bacteria cell detachment from biofilm. The large reduction in ∆ATPs reflects bacteria cell adhesion and biofilm growth on RO membrane surfaces. It is concluded that the temporal increase and decrease in ∆ATP in RO concentrated water capture the dynamic biofouling behavior and the formation process of biofilm on RO membrane surfaces.

Nitrous oxide (N2O) emitted from biological nutrient removal activated sludge systems contributes significantly to the total carbon footprint of modern wastewater treatment plants. In the present study, N2O production and emissions were experimentally determined in a large-scale plant (220,000 PE) employing combined nitrogen (N) and phosphorus (P) removal. As a modelling tool, the Activated Sludge Model 2d (ASM2d) was extended with modules describing multiple N2O production pathways and N2O liquid-gas transfers. The new model was calibrated and validated using the results of laboratory experiments and full-scale measurements. Different operational strategies were evaluated following the proposed model-based procedure. Heterotrophic denitrification was found to be the predominant pathway of N2O production under both anoxic and aerobic conditions. This behaviour could primarily be attributed to the predominant abundance of heterotrophic denitrifiers over nitrifiers. Simulations revealed that the optimal solution for minimizing liquid N2O production is to set the dissolved oxygen concentration in the aerobic zone from 1 to 2 mg O2/L and to enhance the mixed liquor recirculation rate (MLR) (>500% of the influent flowrate) while not compromising effluent standards. Regarding the actual conditions, the potential reduction in the carbon footprint was estimated to be 10% by applying the proposed operational strategy. The results suggest that considerable improvements can be achieved without substantial upgrades and increased costs.

A partial nitritation (PN)/anaerobic ammonium oxidation (ANAMMOX) process in sequencing batch reactor (SBR) was successfully developed to treat high-strength ammonium wastewater. The feed distribution in the SBR cycle and sub-cycles was considered as the main operating strategy, and was optimized using a response surface methodology (RSM)-based optimization technique. In the SBR cycle, the maximum nitrogen removal rate (NRR) of 0.79 ± 0.01 kg m−3 d−1 was achieved by applying a feed distribution strategy that considered the kinetic characteristics of ANAMMOX and ammonia oxidizing bacteria (AOB). However, this strategy negatively affected the nitrogen removal efficiency (NRE) due to alkalinity loss. Therefore, the feed distribution in the SBR sub-cycles with respect to the NRE and the NRR was further studied. The nitrogen removal performance was optimized in the optimum region and an NRE of 88% and an NRR of 0.84 kg m−3 d−1 were achieved. The optimized model was verified in confirmation test. The RSM-based optimization results provide insights into the feed distribution strategy for achieving single-stage PN/ANAMMOX SBR operation.

Sidestream sludge treatment approaches have been developed in recent years to achieve mainstream nitrite shunt or partial nitritation, where NOB are selectively inactivated by biocidal factors such as free nitrous acid (FNA) or free ammonium (FA) in a sidestream reactor. The existence of NOB in raw wastewater has been increasingly realized and could pose critical challenge to stable NOB suppressions in those systems. This study, for the first time, evaluated the impact of influent NOB on the NOB suppressions in a mainstream nitrite shunt system achieved through sidestream sludge treatment. An over 500-day sequential batch reactor operation with six experimental phases rigorously demonstrated the negative effects of influent NOB on mainstream NOB control. Continuously seeding of NOB contained in influent stimulated NOB community shifts, leading to different extents of ineffective NOB suppression. The role of primary wastewater treatment in NOB removal from raw wastewater was also investigated. Results suggest primary settling and High Rate Activated Sludge system could remove a large part of NOB contained in raw wastewater. Primary treatment for raw wastewater is necessary for ensuring stable mainstream NOB suppressions.

Biofouling of seawater reverse osmosis (SWRO) membranes is a major problem that SWRO freshwater production facilities face worldwide. A three-step pretreatment scheme, initially designed to assist the SWRO process in boron rejection, was examined as a potential membrane biofouling inhibitor. The conventional pretreatment procedure in this study includes acidification, CO2 stripping and pH elevation, and its effect on planktonic cell mortality and biofilm formation on the membrane was analyzed. An in-situ electrolytic production of free chlorine in seawater, during the low pH phase, was suggested as an additional pretreatment step, with the goal of serving as an aggressive disinfection course. In addition, 48-hour enhanced biofouling experiments using an RO membrane cell assembly were conducted in order to observe the flux decline pattern as affected by the various treatments. The conventional pretreatment scheme was found to have a moderate effect on membrane biofouling, increasing the membrane permeability by 25% relative to an untreated experimental run. Moreover, the conventional pretreatment did not significantly promote cell mortality; however, it caused an increase in extracellular polysaccharide production during biofilm formation. The additional chlorination step increased the biofouling phenomenon, causing the production of particulate matter, likely due to cell wall oxidation.