Improvement in municipal wastewater treatment alters lake nitrogen to phosphorus ratios in populated regions.

Large-scale and rapid improvement in wastewater treatment is common practice in developing countries, yet this influence on nutrient regimes in receiving waterbodies is rarely examined at broad spatial and temporal scales. Here, we present a study linking decadal nutrient monitoring data in lakes with the corresponding estimates of five major anthropogenic nutrient discharges in their surrounding watersheds over time. Within a continuous monitoring dataset covering the period 2008 to 2017, we find that due to different rates of change in TN and TP concentrations, 24 of 46 lakes, mostly located in China's populated regions, showed increasing TN/TP mass ratios; only 3 lakes showed a decrease. Quantitative relationships between in-lake nutrient concentrations (and their ratios) and anthropogenic nutrient discharges in the surrounding watersheds indicate that increase of lake TN/TP ratios is associated with the rapid improvement in municipal wastewater treatment. Due to the higher removal efficiency of TP compared with TN, TN/TP mass ratios in total municipal wastewater discharge have continued to increase from a median of 10.7 (95% confidence interval, 7.6 to 15.1) in 2008 to 17.7 (95% confidence interval, 13.2 to 27.2) in 2017. Improving municipal wastewater collection and treatment worldwide is an important target within the 17 sustainable development goals set by the United Nations. Given potential ecological impacts on biodiversity and ecosystem function of altered nutrient ratios in wastewater discharge, our results suggest that long-term strategies for domestic wastewater management should not merely focus on total reductions of nutrient discharges but also consider their stoichiometric balance.

Sugar beet industry process wastewater treatment using electrochemical methods and optimization of parameters using response surface methodology.

Sugar production is a water intensive process that produces a large amount of wastewaters with high concentration of chemical oxygen demand (COD), mostly consists of organic carbon compounds. Conventional treatment methods are limited to provide the necessary treatment of effluent COD to meet the regulatory limits prior to discharge. The treatment performance of electrooxidation (EO) and electrochemical peroxidation (ECP) for organic removal were investigated in a laboratory scale study. The experimental conditions were optimized for both EO and ECP using Box-Behnken Design (BBD) and the models provided highly significant quadratic models for both treatment methods. The effects of pH, H2O2 dosage, current density, and operation time were investigated using BBD. The results showed that EO could remove 75% of organics at optimum conditions of pH 5.3; current density of 48.5 mA cm-2; and operation time of 393 min. The predicted values were in reasonable agreement with measured values. ECP could remove total and soluble COD and total and dissolved organic carbon by 65, 64, 66, and 63%, respectively at optimum conditions of H2O2 dosage of 21 mL L-1; current density of 48 mA cm-2; and operation time of 361 min. The methods were compared based on removal efficiency and energy consumption during operation.

Defluoridation of synthetic and industrial wastewater by using acidic activated alumina adsorbent: characterization and optimization by response surface methodology.

Excessive contamination of fluoride in wastewater is the cause of several chronic health problems. For this purpose, an adsorbent was prepared from alumina by acidic activation using sulfuric acid. The current research aims to find the maximum fluoride adsorption (%) from synthetic and industrial wastewater at optimum process parameters by using response surface methodology (RSM). All batch scale experiments were carried out according to the statistical-design order. Central composite design (CCD) was applied to ascertain the effect of adsorbent dose, pH, initial fluoride concentration and temperature on fluoride adsorption (%). Maximum fluoride removal was predicted based on the quadratic model developed. Validation of the model was done with negligible error. The regression coefficient of the model was found to be 0.96. From the analysis of variance (ANOVA), the factors with the greatest effect on the adsorption of fluoride were identified. Under optimized condition, the adsorbent dose 13.89 g L-1, pH 5.52, temperature 25 °C and initial fluoride concentration 18.67 mg L-1 resulted in 96% of maximum fluoride adsorption. Under the same optimized parameters, the fluoride adsorption from industrial wastewater found to be 92.10%.

Multivariate analyses of the effect of an urban wastewater treatment plant on spatial and temporal variation of water quality and nutrient distribution of a tropical mid-order river.

Freshwater resources are increasingly scarce due to human activities, and the understanding of water quality variations at different spatial and temporal scales is necessary for adequate management. Here, we analyze the hypotheses that (1) the presence of a wastewater treatment plant (WWTP) and (2) a polluted tributary that drains downstream from the WWTP change the spatial patterns of physicochemical variables (pH, turbidity, dissolved oxygen, and electrical conductivity) and nutrient concentrations (reactive soluble phosphorus, total phosphorus, nitrogen series, total nitrogen, and total dissolved carbon) along a mid-order river in SE Brazil and that these effects depend on rainfall regime. Six study sites were sampled along almost 4 years to evaluate the impacts of human activities, including sites upstream (1-3) and downstream (5-6) from the WWTP. The impacts were observed presenting an increasing trend from the source (site 1) towards Água Quente stream (site 4, the polluted tributary), with signs of attenuation at site 5 (downstream from both WWTP and site 4) and the river mouth (site 6). Input of nutrients by rural and urban runoff was observed mainly at sites 2 and 3, respectively. At sites 4 and 5, the inputs of both untreated and treated wastewaters increased nutrient concentrations and changed physicochemical variables, with significant impacts to Monjolinho River. Seasonal variations in the measured values were also observed, in agreement with the pluviometric indexes of the region. Univariate analyses suggested no effect of the WWTP for most variables, with continued impacts at sites downstream, but non-parametric multivariate analysis indicated that these sites were recovering to chemical characteristics similar to upstream sites, apparently due to autodepuration. Therefore, multivariate methods that allow rigorous tests of multifactor hypotheses can greatly contribute to determine effects of both point and non-point sources in river systems, thus contributing to freshwater monitoring and management.

Optimization of operating parameters of novel composite adsorbent for organic pollutants removal from POME using response surface methodology.

The present work aimed to develop a novel composite material made up of activated cow bone powder (CBP) as a starting material for reducing chemical oxygen demand (COD) and ammonia-nitrogen (NH3N) from palm oil mill effluent (POME). The optimization of the reduction efficiency was investigated using response surface methodology (RSM). Six independent variables used in the optimization experiments include pH (4-10), speed (0.27-9.66 rcf), contact time (2-24 h), particle size (1-4.35 mm), dilution factor (100-500) and adsorbent dosage (65-125 g/L). The chemical functional groups were determined using Fourier transform irradiation (FTIR). The elemental composition were detected using SEM-EDX, while thermal decomposition was investigated using thermo gravimetric analysis (TGA) in order to determine the effects of carbonization temperature on the adsorbent. The results revealed that the optimal reduction of COD and NH3N from raw POME was observed at pH 10, 50 rpm, within 2 h and 3 mm of particle size as well as at dilution factor of 500 and 125 g L-1 of adsorbent dosage, the observed and predicted reduction were 89.60 vs. 85.01 and 75.61 vs. 74.04%, respectively for COD and NH3N. The main functional groups in the adsorbent were OH, NH, CO, CC, COC, COH, and CH. The SEM-EDX analysis revealed that the CBP-composite has a smooth surface with high contents of carbon. The activated CBP has very stable temperature profile with no significant weight loss (9.85%). In conclusion, the CBP-composite investigated here has characteristics high potential for the remediation of COD and NH3N from raw POME.

Determination of the priority substances regulated by 2000/60/EC and 2008/105/EC Directives in the surface waters supplying water treatment plants of Athens, Greece.

An investigation into the occurrence of priority substances regulated by 2000/60/EC Water Framework Directive and 2008/105/EC Directive was conducted for a period of one year in the surface water sources supplying the water treatment plants (WTPs) of Athens and in the raw water of WTPs. Samples from four reservoirs and four water treatment plants of Athens were taken seasonally. The substances are divided into seven specific groups, including eight volatile organic compounds (VOCs), diethylhexylphthalate, four organochlorine pesticides (OCPs), three organophosphorus/organonitrogen pesticides (OPPs/ONPs), four triazines and phenylurea herbicides, pentachlorophenol, and four metals. The aforementioned substances belong to different chemical categories, and different analytical methods were performed for their determination. The results showed that the surface waters that feed the WTPs of Athens are not burdened with significant levels of toxic substances identified as European Union (EU) priority substances. Atrazine, hexachlorocyclohexane, endosulfan, trifluralin, anthracene and 4-nonylphenol were occasionally observed at very low concentrations. Their presence in a limited number of cases could be attributed to waste disposal, agricultural activities, and to a limited industrial activity in the area nearby the water bodies.

Elimination of persistent emerging micropollutants in a suspended-bed photocatalytic reactor: influence of operating conditions and combination with aerobic biological treatment.

A larger, lab-scale photocatalytic suspended-bed reactor using TiO2 sol-gel-coated expanded clay granules as a bed material was evaluated for oxidative removal of the persistent pharmaceuticals doxycycline, prednisolone, amoxicillin, and sulfamethizole, as well as their mixture, in ppm concentrations. The photocatalytic degradation potential of drug molecules increases as their adsorption affinity increases towards TiO2-containing coatings. The performance of the photocatalytic reactor in the removal of drugs was improved by optimizing the fluidization process parameters. The reactor operation at high bed loadings is determined by the abrasion resistance of the catalyst coating. The long-term stability of the coated bed was enhanced by optimal loading, achieving a higher removal rate while placing moderate mechanical stress on the coated granules. The photocatalytic pretreatment decreased the toxicity of doxycycline solutions to several bacterial strains, including the environmental bacterium Pseudomonas putida and bacterial strains freshly isolated from the activated sludge. The treatment of doxycycline-containing water with a combination of photocatalytic treatment and bio-oxidation resulted in 98% removal of the target in the bioreactor outlet, with no deterioration in the operation of the biological process.

Review of soluble uranium removal by nanoscale zero valent iron.

Uranium (U) has been released to surface soil and groundwater through military and industrial activities. Soluble forms of U transferred to drinking water sources and food supplements can potentially threaten humans and the biosphere due to its chemical toxicity and radioactivity. The immobilization of aqueous U onto iron-based minerals is one of the most vital geochemical processes controlling the transport of U. As a consequence, much research has been focused on the use of iron-based materials for the treatment of U contaminated waters. One material currently being tested is nanoscale zero-valent iron (nZVI). However, understanding the removal mechanism of U onto nZVI is crucial to develop new technologies for contaminated water resources. This review article aims to provide information on the removal mechanism of U onto nZVI under different conditions (pH, U concentration, solution ion strength, humic acid, presence of O2 and CO2, microorganism effect) pertinent to environmental and engineered systems, and to provide risk or performance assessment results with the stability of nZVI products after removal of U in environmental restoration.

Managing Scarce Water Resources in China's Coal Power Industry.

Coal power generation capacity is expanding rapidly in the arid northwest regions in China. Its impact on water resources is attracting growing concerns from policy-makers, researchers, as well as mass media. This paper briefly describes the situation of electricity-water conflict in China and provides a comprehensive review on a variety of water resources management policies in China's coal power industry. These policies range from mandatory regulations to incentive-based instruments, covering water withdrawal standards, technological requirements on water saving, unconventional water resources utilization (such as reclaimed municipal wastewater, seawater, and mine water), water resources fee, and water permit transfer. Implementing these policies jointly is of crucial importance for alleviating the water stress from the expanding coal power industry in China.

The application of multi-objective optimization method for activated sludge process: a review.

The activated sludge process (ASP) is the most generally applied biological wastewater treatment approach. Depending on the design and specific application, activated sludge wastewater treatment plants (WWTPs) can achieve biological nitrogen (N) and phosphorus (P) removal, besides the removal of organic carbon substances. However, the effluent N and P limits are getting tighter because of increased emphasis on environmental protection, and the needs for energy conservation as well as the operational reliability. Therefore, the balance between treatment performance and cost becomes a critical issue for the operations of WWTPs, which necessitates a multi-objective optimization (MOO). Recent studies in this field have shown promise in utilizing MOO to address the multiple conflicting criteria (i.e. effluent quality, operation cost, operation stability), including studying the ASP models that are primarily responsible for the process, and developing the method of MOO in the wastewater treatment process, which facilitates better optimization of process performance. Based on a better understanding of the application of MOO for ASP, a comprehensive review is conducted to offer a clear vision of the advances, and potential areas for future research are also proposed in the field.

Anaerobic digestion of post-hydrothermal liquefaction wastewater for improved energy efficiency of hydrothermal bioenergy processes.

Hydrothermal liquefaction (HTL) is a promising process for converting wet biomass and organic wastes into bio-crude oil. It also produces an aqueous product referred to as post-hydrothermal liquefaction wastewater (PHWW) containing up to 40% of the original feedstock carbon, which reduces the overall energy efficiency of the HTL process. This study investigated the feasibility of using anaerobic digestion (AD) to treat PHWW, with the aid of activated carbon. Results showed that successful AD occurred at relatively low concentrations of PHWW (≤ 6.7%), producing a biogas yield of 0.5 ml/mg CODremoved, and ∼53% energy recovery efficiency. Higher concentrations of PHWW (≥13.3%) had an inhibitory effect on the AD process, as indicated by delayed, slower, or no biogas production. Activated carbon was shown to effectively mitigate this inhibitory effect by enhancing biogas production and allowing digestion to proceed at higher PHWW concentrations (up to 33.3%), likely due to sequestering toxic organic compounds. The addition of activated carbon also increased the net energy recovery efficiency of AD with a relatively high concentration of PHWW (33.3%), taking into account the energy for producing activated carbon. These results suggest that AD is a feasible approach to treat PHWW, and to improve the energy efficiency of the HTL processes.

Application of the QUAL2K model to design an ecological purification scheme for treated effluent of a wastewater treatment plant.

Treated effluent from wastewater treatment plants has become an important source of excess nutrients causing eutrophication in water. In this study, an ecological purification method was used to further treat eutrophic water. A three-season ecological purification scheme which comprised an emergent plant (Eme.), a submerged plant (Sub.) and a novel biological rope (Bio.), was designed for the treated effluent canal of a wastewater treatment plant. The removal parameters determined from the experiment were input into a QUAL2K model to simulate downstream water quality of the treated effluent canal. Respective removal rates of total nitrogen and total phosphorus of the Eme., Sub. and Bio. were 32.48-37.33% and 31.63-39.86% in summer, 14.12-33.61% and 17.74-23.80% in autumn, and 14.13-18.03% and 10.05-12.75% in winter, with 1-day reaction time. Optimal combinations for summer, autumn/spring, and winter are Eme. + Bio., Eme. + Bio. + Sub., and Sub. + Bio., respectively. Simulated load reduction rates of total nitrogen and total phosphorus for the treated effluent canal were 42.64-78.40% and 30.98-78.29%, respectively, year round with 2.5-day reaction time. This study provides an efficient evaluation and design method for ecological purification engineering.

Application of membrane processes in fractionation of elements in river water.

The influence of wastewater treatment plant (WWTP) effluents from one microelectronic industrial zone on element concentrations and partitioning in river water was investigated. The stepwise membrane filtration is used to distinguish different size fractions including large particulate (>18 µm), particulate (0.2-18 µm), colloidal/nanoparticle (10 kDa-0.2 µm) and truly dissolved fractions (<10 kDa) in river water samples and WWTP effluents. Results demonstrated that anthropogenic inputs (WWTP effluents and industrial area) had an important influence on concentrations and partitioning of some elements in river water. Mass balance results showed that membrane filtration processes could realize a good fractionation for many elements (good recoveries) in water samples. Flux decline during 0.2 µm and 10 kDa filtrations were analyzed, and corresponding fouling mechanisms are discussed.

Global and local health burden trade-off through the hybridisation of quantitative microbial risk assessment and life cycle assessment to aid water management.

Life cycle assessment (LCA) and quantitative risk assessment (QRA) are commonly used to evaluate potential human health impacts associated with proposed or existing infrastructure and products. Each approach has a distinct objective and, consequently, their conclusions may be inconsistent or contradictory. It is proposed that the integration of elements of QRA and LCA may provide a more holistic approach to health impact assessment. Here we examine the possibility of merging LCA assessed human health impacts with quantitative microbial risk assessment (QMRA) for waterborne pathogen impacts, expressed with the common health metric, disability adjusted life years (DALYs). The example of a recent large-scale water recycling project in Sydney, Australia was used to identify and demonstrate the potential advantages and current limitations of this approach. A comparative analysis of two scenarios - with and without the development of this project - was undertaken for this purpose. LCA and QMRA were carried out independently for the two scenarios to compare human health impacts, as measured by DALYs lost per year. LCA results suggested that construction of the project would lead to an increased number of DALYs lost per year, while estimated disease burden resulting from microbial exposures indicated that it would result in the loss of fewer DALYs per year than the alternative scenario. By merging the results of the LCA and QMRA, we demonstrate the advantages in providing a more comprehensive assessment of human disease burden for the two scenarios, in particular, the importance of considering the results of both LCA and QRA in a comparative assessment of decision alternatives to avoid problem shifting. The application of DALYs as a common measure between the two approaches was found to be useful for this purpose.

Environmental profile of typical anaerobic/anoxic/oxic wastewater treatment systems meeting increasingly stringent treatment standards from a life cycle perspective.

Stringent new legislation for wastewater treatment plants (WWTPs) is currently motivating innovation and optimization of wastewater treatment technologies. Evaluating the environmental performance of a wastewater treatment system is a necessary precursor before proposing implementation of WWTPs designed to address the global requirements for reduced resource use, energy consumption and environmental emissions. However, developing overly-sophisticated treatment methods may lead to negative environmental effects. This study was conducted to employ a process modeling approach from a life cycle perspective to construct and evaluate six anaerobic/anoxic/oxic wastewater treatment systems that include a water line, sludge line and bioenergy recovery system and was designed to meet different treatment standards in China. The results revealed that improved treatments optimized for local receiving watercourses can be realized at the cost of higher resource consumption and greenhouse gas emissions. Optimal Scenarios were also identified from different positive perspectives.

Performance and microbial community analysis of a novel bio-cord carrier during treatment of a polluted river.

The performance and microbial community structure of a novel bio-cord carrier during treatment of a polluted river at the laboratory scale was investigated. The bio-cord exhibited good filtration performance, with 87.2% SS removal and an 84.9% reduction in turbidity in 120 min, as well as 19.4-34.4%, 55.2-74.0%, 46.2-55.9% and 13.1-18.5% reductions in the COD, NH3-N, TN and TP, respectively, under three different hydraulic retention times. The bio-cord fibers also provided suitable conditions and support media for microbial growth. Additionally, 114 cloned 16S rDNA sequences were composed of Proteobacteria (57.9%), Bacteroidetes (17.5%) and other phyla (24.6%). There were great differences in bacterial quantity and composition between the surface and inside of the bio-cord. Furthermore, nitrifying and denitrifying bacteria were detected, suggesting that simultaneous nitrification and denitrification processes were occurring. Overall, the results of this study demonstrated that the carrier could attach microorganisms for polluted river treatment.

WEF/WERF study of BNR plants achieving very low N and P limits: evaluation of technology performance and process reliability.

The Water Environment Research Foundation (WERF) funded a two-year comprehensive study of nutrient removal plants designed and operated to meet very low effluent total nitrogen (TN) and total phosphorus (TP) concentrations. WERF worked with the Water Environment Federation (WEF) to solicit participation of volunteers and provide a forum for information exchange at workshops at its annual conferences. Both existing and new technologies are being adapted to meet requirements that are as low as 3.0 mg/L TN and 0.1 mg/L TP, and there is a need to define their capabilities and reliabilities in the real world situation of wastewater treatment plants. A concern over very low daily permits for ammonia caused the work to be extended to include nitrification reliability. This effort focused on maximizing what can be learned from existing technologies in order to provide a database that will inform key decision makers about proper choices for both technologies and rationale bases for statistical permit writing. To this end, managers of 22 plants, 10 achieving low effluent TP, nine achieving low effluent TN, and three achieving low effluent NH(3)-N, provided three years of operational data that were analyzed using a consistent statistical approach. Technology Performance Statistics (TPSs) were developed as three separate values representing the ideal, median, and reliably achievable performance. Technological conclusions can be drawn from the study in terms of what can be learned by comparing the different nutrient removal and nitrification processes employed at these 22 plants.

Recycled water: potential health risks from volatile organic compounds and use of 1,4-dichlorobenzene as treatment performance indicator.

Characterisation of the concentrations and potential health risks of chemicals in recycled water is important if this source of water is to be safely used to supplement drinking water sources. This research was conducted to: (i) determine the concentration of volatile organic compounds (VOCs) in secondary treated effluent (STE) and, post-reverse osmosis (RO) treatment and to; (ii) assess the health risk associated with VOCs for indirect potable reuse (IPR). Samples were examined pre and post-RO in one full-scale and one pilot plant in Perth, Western Australia. Risk quotients (RQ) were estimated by expressing the maximum and median concentration as a function of the health value. Of 61 VOCs analysed over a period of three years, twenty one (21) were detected in STE, with 1,4-dichlorobenzene (94%); tetrachloroethene (88%); carbon disulfide (81%) and; chloromethane (58%) most commonly detected. Median concentrations for these compounds in STE ranged from 0.81 µg/L for 1,4-dichlorobenzene to 0.02 µg/L for carbon disulphide. After RO, twenty six (26) VOCs were detected, of which 1,4-dichlorobenzene (89%); acrylonitrile (83%) chloromethane (63%) and carbon disulfide (40%) were the more frequently detected. RQ(max) were all below health values in the STE and after RO. Median removal efficiency for RO was variable, ranging from -77% (dichlorodifluoromethane) to 91.2% (tetrachloroethene). The results indicate that despite the detection of VOCs in STE and after RO, their human health impact in IPR is negligible due to the low concentrations detected. The results indicate that 1,4-dichlorobenzene is a potential treatment chemical indicator for assessment of VOCs in IPR using RO treatment.

Experiences on dual media filtration of WWTP effluent.

This research is legislation driven by the European Water Framework Directive (WFD) and the Dutch Fourth Memorandum on Water Management. The objective of this research is to achieve the removal of total nitrogen and total phosphorus by Dual Media Filtration. The target value during this research for total nitrogen is 2.2 mg/L and for total phosphorus 0.15 mg/L. The results show that for NOx-N concentrations in the WWTP effluent up to 10 mg/L, a stable operation of the process can be reached with removal rates of 80% to 90%. The maximum nitrogen removal rate was 3.5 kg N/(m3.d). Above 10 mg/L a risk of filter bed clogging occurred. When the orthophosphorus concentration in the WWTP effluent exceeds the maximum of 0.3 mg/L, the total phosphorus concentration in the filtrate water will exceed the target value of 0.15 mg P-total/L. Temperature has a large impact in the phosphorus removal; the optimum temperature range is within 13 degrees C-18 degrees C. In conclusion, Dual Media Filtration is capable of producing reusable water with total phosphorus concentrations of <0.15 mg/L, under the condition that the wastewater treatment plant produces WWTP effluent with steady concentrations for orthophosphorus (<0.3 mg PO4-P/L). To reach total nitrogen concentrations in the filtrate water of <2.2 mg/L a NOx-N removal efficiency of nearly 100% is required.

Performance of suspended and attached growth MBR systems in treating high strength synthetic wastewater.

The performance of laboratory-scale attached growth (AG) and suspended growth (SG) membrane bioreactors (MBRs) was evaluated in treating synthetic wastewater simulating high strength domestic wastewater. This study investigated the influence of sponge suspended carriers in AG-MBR system, occupying 15% reactor volume, on the removal of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP), and compared it to that of SG-MBR. Results showed that the removal efficiencies of COD, TN and TP in AG-MBR were 98%, 89% and 58%, respectively as compared to 98%, 74% and 38%, respectively in SG-MBR. Improved TN removal in AG-MBR systems was primarily based on simultaneous nitrification and denitrification (SND) process. These results infer that the presence of small bio-particles having higher microbial activity and the growth of complex biomass captured within the suspended sponge carriers resulted in improved TN and TP removal in AG-MBR.