Municipal Treatment Plant Research Articles

Removal of odors and VOCs in municipal solid waste comprehensive treatment plants using a novel three-stage integrated biofilter: Performance and bioaerosol emissions.

A novel three-stage integrated biofilter (TSIBF) composed of acidophilic bacteria reaction segment (ABRS), fungal reaction segment (FRS) and heterotrophic bacteria reaction segment (HBRS) was constructed for the treatment of odors and volatile organic compounds (VOCs)from municipal solid waste (MSW) comprehensive treatment plants. The performance, counts of predominant microorganisms, and bioaerosol emissions of a full-scale TSIBF system were studied. High and stable removal efficiencies of hydrogen sulfide, ammonia and VOCs could be achieved with the TSIBF system, and the emissions of culturable heterotrophic bacteria, fungi and acidophilic sulfur bacteria were relatively low. The removal efficiencies of different odors and VOCs, emissions of culturable microorganisms, and types of predominant microorganisms were different in the ABRS, FRS and HBRS due to the differences in reaction conditions and mass transfer in each segment. The emissions of bioaerosols from the TSIBF depended on the capture of microorganisms and their volatilization from the packing. The rational segmentation, filling of high-density packings and the accumulation of the predominant functional microorganisms in each segment enhanced the capture effect of the bioaerosols, thus reducing the emissions of microorganisms from the bioreactor.

Quantile regression with a metal oxide sensors array for methane prediction over a municipal solid waste treatment plant

Abstract Methane leakage is a crucial issue regarding its potential Green House effect. This study developed a quantile regression model for methane estimation over a municipal solid waste treatment plant (MSW) subject to biogas leakages and monitored with MOS gas sensors. Experimental data from 6 MOS gas sensors and a methane FID analyser taken during fourth months have been used for that purpose. The data processing consisted of (i) a drift correction, (ii) the addition of interactions, (iii) a principal component analysis (PCA) to extract new uncorrelated predictors, and (iv) a log transform of the methane data distribution. The forecast ability of the derived field calibrated model, compared with results from PLS regression, indicates well how helpful has been the data processing methods. Moreover, it highlighted, with some caution, the interest in using the quantile regression and interactions for models with MOS gas sensors considering the cross-sensitivity.

The Use of Chemical Sensors to Monitor Odour Emissions at Municipal Waste Biogas Plants

Municipal waste treatment plants are an important element of the urban area infrastructure, but also, they are a potential source of odour nuisance. Odour impact from municipal waste processing plants raises social concerns regarding the well-being of employees operating the plants and residents of nearby areas. Chemical methods involve the determination of the quantitative composition of compounds comprising odour. These methods are less costly than olfactometry, and their efficiency is not dependent on human response. The relationship between the concentration of a single odorant and its odour threshold (OT) is determined by the odour activity value (OAV) parameter. The research involved the application of a multi-gas detector, MultiRae Pro. Measurements by means of the device were conducted at three municipal waste biogas plants located in Poland. In this paper we describe the results obtained when using a detector during the technological processes, the unitary procedures conducted at the plants, and the technological regime. The determination of these relationships could be useful in the development of odour nuisance minimization procedures at treatment plants and the adjustment to them. This is of paramount importance from the viewpoint of the safety and hygiene of the employees operating the installations and the comfort of residents in the areas surrounding biogas plants. Monitoring of expressed odorant emissions allows the course of technological processes and conducted unit operations to be controlled.

Nanofiltration to Purify Drinking Water from Cyanobacteria and Microcystins in Water Supply Systems

The pollution of a surface water supply source (Kuibyshev reservoir) with cyanobacterial metabolites under the conditions of the increased biogenic load has been estimated. During the period of mass growth of Cyanobacteria, the reservoir water quality deteriorates in some indicators, including the smell, taste, and content of organic and toxic substances. Among the wide range of cyanotoxins, microcystin-LR, the permissible concentration of which in drinking water should not exceed 1 μg/dm3, poses the greatest threat to the population. Global warming creates favorable conditions for the rapid growth of Cyanobacteria, therefore, the issue of providing the population with high-quality drinking water will further become aggravated.Conventional process lines at municipal water treatment plants are ineffective in removing intracellular and extracellular cyanotoxins. The best and safest barrier against the ingress of cyanotoxins into drinking water can be membrane technologies that allow ultrafiltration of bacterial cells without mechanical damage and nanofiltration of cyanotoxins dissolved in water.

Investigation of effective factors on the ammonia removal efficiency in the wastewater treatment plants using the air stripping process

Removal of ammonia from wastewater in the wastewater treatment plants due to its dangerous and toxic effects on human health and biotic resources is essential. This study was aimed to investigate the effective operational parameters on the efficiency of the air stripping process, determine their priority and degree of effect on ammonia removal and compare the ammonia removal efficiency during the air stripping process in the municipal treatment plants using synthetic and real wastewater.In this study, the effect of each operating parameter on the ammonia removal efficiency including initial ammonia concentration, pH and temperature during the air stripping process for synthetic and real wastewater, respectively, based on standard methods (the Nesslerization method, preparation of standard solutions) using a spectrophotometer, pH meter and temperature module were evaluated.The results of this study showed that the maximum of ARE for synthetic wastewater with Air to water ratio 80 and an initial ammonia concentration of 59. 6 mg /l, pH 12.05 and temperature 46.3°C was %91. Also, the results of the study on the ARE during the air stripping process showed that the maximum of ARE (%91) for real wastewater (primary sedimentation tank effluent (PST)) with Air to water ratio 80 and an initial ammonia concentration of 61.04 mg/l, pH 12.53 and temperature 45.9 ° C was obtained.Based on the results of univariate regression model, initial ammonia concentration˃ temperature˃ pH have the greatest effect on the ammonia removal efficiency in synthetic wastewater and real wastewater, respectively. In the multivariate regression model, the effect of temperature and pH on the ammonia removal efficiency in synthetic and real wastewater is increasing and decreasing, respectively. Based on the findings of this study, the air stripping process can be successfully used to remove ammonia from wastewater in the municipal treatment plants, especially in the tropics.

Nonylphenol, Octylphenol, and Nonylphenol Ethoxylates Dissemination in the Canadian Freshwater Environment.

Nonylphenol, octylphenol, and nonylphenol ethoxylates are manmade compounds that are only discharged in the environment due to anthropogenic activities. The objectives of this study were to determine the current concentrations of these substances in the Canadian freshwater environment and to determine if past regulatory actions were beneficial to the environment. Freshwater samples (n = 241) were collected and analysed for 4-nonylphenols (NP), nonylphenol monoethoxylate (NP1EO), nonylphenol diethoxylate (NP2EO), and octylphenols at 35 sites in Canada from 2014 to 2019 with individual compound concentrations ranging from 1.29 to 477.22ng/L. In addition, 18-65% of the samples were reported to be under the laboratory detection limit, depending on the compound. Sampling sites were categorised into five groups based on the dominant activities present upstream in their watersheds: mixed use sites; municipal waste water treatment plant (MWWTP)-associated sites; textile mill-associated sites; urban; and reference sites. All four compounds in the study were detected more frequently in urban and MWWTP-associated sites than at other locations. Additionally, there is a statistically significant (p < 0.05) downward temporal trend in NP concentrations in Canadian surface waters from 2014 to 2019. There were no exceedances of the Canadian Water Quality Guideline of 1000ng/L.

Project specifics for the construction of a municipal solid waste treatment plant

Environmental trends and growing tendency to think about ecology play an important role in the development of modern industry. Significant role in this field takes a construction of plants for the processing of municipal solid waste, contributing to the neutralization of the harmful effects by different waste. This article represents development and stages of project implementation for the plant OOO «Kamskoye» that works with solid municipal waste in the city of Chaykovsky, Perm Territory. Investment efficiency of the construction of this facility was calculated. A model of interaction between business and government bodies, which regulate investment to waste disposal projects, is presented. The main structural elements of construction of a plant for processing municipal solid waste are shown. The project was developed using a public-private partnership model. The implementation of the project will ensure the production of secondary raw materials for its further use as an alternative source of heat and electricity generation, as well as the use of products necessary for the market in the production process. The main feature and advantage of the project is the possibility of using a principle «waste to income», which allows to provide your production with energy resources from reusable waste.

Cause of Failure of Municipal Waste Water Treatment Plant in Narayanghad

Constructed wetland (CW), combined with other physical treatment units, is considered as an environmentally friendly and sustainable option for waste water treatment of varying scale. The absence of mechanical system makes the CW a low maintenance system but not maintenance free. The maintenance free treatment plant concept was observed in municipal waste water treatment plant in Narayanghad, Nepal largely because of its poor maintenance. Due to the absence of maintenance for a long time, sludge from the primary treatment units started to flow to the wetlands which, in turn, caused the reed plant to wither. From different literatures it was found that high organic solid load was the prime cause for the clogging of the filter medium. Clogging triggered oxygen deficiency at the root of the plant and hindered its growth.

Applications of UV/H2O2, UV/persulfate, and UV/persulfate/Cu2+ for the elimination of reverse osmosis concentrate generated from municipal wastewater reclamation treatment plant: Toxicity, transformation products, and disinfection byproducts

Reverse osmosis concentrate (ROC) resulting from treatment of municipal wastewater reclamation involves high concentrations of recalcitrant pollutants. This study evaluated the toxicity of an ROC containing harmful biocides during representative UV synergistic oxidation processes (SOPs) (e.g., UV/hydrogen peroxide (H2O2), UV/persulfate (PS), and UV/PS/Cu2+). Treated ROC exhibited up to 1.3–2.3 times higher toxicity than the parent compounds such as dodecyl trimethyl ammonium chloride (DTAC) and dodecyl dimethyl benzyl ammonium chloride (DDBAC). Based on the intermediates identification, the major toxic intermediates were screened through silico assessment using the quantitative Ecological Structure-Activity Relationship (ECOSAR) tool. The transformation products (TPs) of hydroxylation and ketonization were the major formed reactions from the UV/PS/Cu2+. Also, some cytotoxic TPs were accumulated during the UV/H2O2 and UV/PS oxidations, where the carbonaceous-disinfection byproducts were more than the nitrogenous-disinfection byproducts. In the presence of chloride and bromide, chlorate and bromate could be formed during the UV-SOP; they were influenced by the different water matrix in comparison with the different ROC. Also, the formation of the total organic halogen species (TOX) was found to follow this order: UV/PS/Cu2+ < UV/H2O2 < UV/PS. In this study, the predicted cytotoxicity using the correlation between the TOX and the cytotoxicity was more acceptable than that of the cytotoxicity index method. Further, the R-square of the correlation between the TOX and the cytotoxicity for the UV/H2O2 and UV/PS was 0.82 and 0.79, respectively. The predicted cytotoxicity using the TOX correlation method in the ROC could also be used to monitor and prevent the application of different oxidations in municipal wastewater reclamation treatment plants.

Study of the Efficiency of Sludge Conditioning by the Method of Advanced Oxidation Process (AOP) During Dewatering of Excess Activated Sludge

The issue of sludge disposal is a complex task that needs to be addressed, taking into account not only economic indicators but also local conditions, such as: the availability of existing sewage treatment plant infrastructure, energy availability, climatic conditions and so on. Currently, more and more municipal enterprises in European countries are building sludge incineration plants. Preparation of sludge for incineration occupies a significant part of the budget since its humidity and caloric content have the greatest impact on the parameters of the sludge incineration unit and its energy balance. Chamber-membrane filter presses are one of the few types of equipment that allows to ensure the maximum reduction of sludge moisture, and the possibility of its completion with heat treatment systems in one closed housing make it an even more attractive solution for small and medium wastewater treatment plants. Of great interest at the present stage of development of wastewater treatment and sludge disposal technology is the technology of advanced oxidation of AOR, which allows to remove biologically stable organic pollutants and leads to inactivation of pathogenic microorganisms. The purpose of this stage was to evaluate the possibility of using the technology of advanced oxidation of AOP for conditioning sludge of municipal treatment plants before their mechanical dehydration and to determine the technological parameters of the sludge filtration process. The studies included laboratory and industrial tests. Based on the research, it was found that AOP technology can be used to reduce the consumption of reagents (iron, lime) in the conditioning of municipal sewage sludge in the case of filtration on a chamber-membrane filter press. The most economically and technologically optimal ratio of Fe / Ca / H2O2 is equal to 2/5/1 at the dosage of hydrogen peroxide H2O2 at the level of 1 g / l. At the proposed dosages of reagents, it is possible to obtain a filtration sludge with a residual moisture content of 64–65% compared to 72–73% using only iron and lime (initial dry matter content in the sludge at 3%).

Cost Optimization of Wastewater and Septage Treatment Process

Analysis of the current knowledge has revealed the lack of a method for increasing the cost-effectiveness of wastewater and septage treatment in plants overloaded by contamination. This was the premise for undertaking research on the process of septage pre-treatment in a subsurface vertical flow constructed wetland (SS-VF) prior to its input into the biological section of a municipal treatment plant. In previous research the authors have indicated that this allows for a significant reduction in the value of pollution indicators. The objective of this paper is to assess the cost-effectiveness of this process by means of an optimization model. The decision variable was the coefficient of septage stream distribution into the quantity directed to the SS-VF bed in relation to its total quantity. The optimization criterion was the minimization of the expected annual cost of wastewater and septage treatment. Verification of the model has shown that it is reasonable to subject all septage to the pre-treatment in a SS-VF bed for small wastewater treatment plant (WWTPs) located in rural areas. The bigger the septage pollution load is, the greater the reduction in the treatment costs. The proposed solution is less cost-effective in urban areas, where the construction of a SS-VF bed requires land purchase and additional costs of its adjustment. Optimization results largely depend on the cost function, so it is important to build it on reliable local data.

Recycling of Organic Wastes through Composting: Process Performance and Compost Application in Agriculture

Composting has become a preferable option to treat organic wastes to obtain a final stable sanitized product that can be used as an organic amendment. From home composting to big municipal waste treatment plants, composting is one of the few technologies that can be practically implemented at any scale. This review explores some of the essential issues in the field of composting/compost research: on one hand, the main parameters related to composting performance are compiled, with especial emphasis on the maturity and stability of compost; on the other hand, the main rules of applying compost on crops and other applications are explored in detail, including all the effects that compost can have on agricultural land. Especial attention is paid to aspects such as the improvement of the fertility of soils once compost is applied, the suppressor effect of compost and some negative experiences of massive compost application.

Can Material and Energy Be Saved by Differentiating Water Quality Targets in the Water Purification Process?

The current organization of water supply systems demands drinking standards for all the households’ usage of water. Few dual water systems, i.e., systems in which the quality of the water supplied is differentiated by types of use, exist but are mainly circumscribed to developing countries. Besides, bath and showers are so far considered as a potable use of water despite only drinking and cooking activities requiring the high-quality standards of potable water. The present work demonstrates how the principles of dual water systems can be incorporated into the sustainable concept of product-service system (PSS) using a dual water system of a municipal water supply treatment plant in France as a case study. The PSS is based on the water quality, and the bathing activity of households is considered with a dedicated standard for the first time. Two systems are considered, S1 and S2, supplied with the same raw water quality and treated with drinking (S1) bathing standards (S2). The quality parameters considered are total organic carbon (TOC) and turbidity (T) and the potential savings related to costs, material, and energy consumptions are assessed using EVALEAU as a process modeling tool. The treatment lines consisted of powdered activated carbon (PAC) addition, coagulation, flocculation, settling, and rapid sand filtration. Results show that material consumption can be reduced by 41% mainly through the decrease in chemical consumption associated with the change of requirement for the TOC parameter. On the opposite, energy consumption was found dependent on the water of volume treated rather than its quality leading to only marginal savings. The cost was decreased by 37% as a result of the reduction of the chemicals consumed.

Heavy Metals in Wastewater and Sewage Sludge from Selected Municipal Treatment Plants in Eastern Cape Province, South Africa

This study assessed the distribution of five heavy metals (Cd, Pb, Cu, Zn, and Fe) across the various stages of treatment in three selected sewage treatment facilities and their receiving waterbodies in the Eastern Cape Province, South Africa. Aqueous and solid (sludge) samples were collected monthly from September 2015 to February 2016. Quantitation was achieved by atomic absorption spectrometry after necessary sample preparations. Concentrations of heavy metal cations in the sludge generally varied from &lt;DL (below detection limit) to 1.17 mg kg−1, &lt;DL to 0.14 mg kg−1, 27.588 to 69.789 mg kg−1, and &lt;DL to 0.099 mg kg−1 for Cu, Cd, Fe and Pb; while Zn was below detection all through. Similarly, the levels of Cu, Cd, and Fe in the influents, effluents, upstream and downstream across the three plants ranged from &lt;DL–6.588 mg L−1, &lt;DL–0.636 mg L−1, &lt;DL–0.878 mg L−1 and &lt;DL–0.711 mg L−1, respectively; Zn and Pb were less than DL in all the matrices and study locations. All the contaminants were below hazardous levels in all the sludge and aqueous samples except Cd which was higher in effluents and surface waters across the board. Wastewater Treatment Plant (WWTP)-A exhibited better removal capacity for Fe (86.6%), compared to WWTP-B (34.7%) and WWTP-C (56.9%). However, the removal of Cu and Zn was very poor in all the treatment facilities studied. Carcinogenic and non-carcinogenic risks evaluated were sufficiently low. This suggests that the levels of contamination, even with respect to Cd, was minimal. Nevertheless, efforts should be made to keep the concentrations of these contaminants at levels safe for humans and aquatic organisms. Furthermore, the use of the effluents from these facilities for irrigation should be discouraged to prevent unnecessary build-up of metals in the soil and plants grown with such, as well as subsequent bioaccumulation and biomagnification in the food chain.

Modern biopositive technologies of waste processing in the utilities and construction industries

Introduction. In this article the analysis of certain biopositive technologies applied to processing or recycling of construction waste, municipal sewage, and paste-like slurries of organo-mineral nature is performed. The relevance of this research is confirmed by the steadily growing number of publications and currently implemented government programmes aimed at solving such problems. The paper summarizes the results of research into the treatment of wastes having different origin.&#x0D; Materials and methods. The analysis of the research literature and patents for inventions, as well as publicly available technologies used in waste processing and recycling is performed. Selection of biopositive technologies based on the chemical nature of materials and their groups is described. Biopositive technologies, most effectively applied to construction materials, are identified for the purpose of converting engineering structures into secondary raw components. The co-authors demonstrate the application of a biopositive technology to sludge decontaminated at municipal waste water treatment plants and to hot waste generated by the hydrolysis industry, as well as technologies used to process special thermal insulation and waterproofing materials.&#x0D; Results. The use of water-organic emulsions as active components in effective regeneration of asphalt granulated concrete mixtures is considered. Сompositions, concentrations and sedimentation stability of such emulsions have been identified. The results of the study of physical, mechanical and hydro-physical properties of the asphalt-concrete granulate treated with water-organic emulsions are described. This regeneration technology helps bitumen to restore binding properties on the surface of the asphalt-concrete granulate and makes this composite applicable as a material designated for the bottom layers of the road pavement.&#x0D; Conclusions. These biopositive technologies make it possible to efficiently and rationally process or recycle a wide range of municipal and construction waste into structures and products having various applications. Recycling, composting and plasma technologies are considered in this case.

Operating parameters optimization of combined UF/NF dual-membrane process for brackish water treatment and its application performance in municipal drinking water treatment plant

As an important water resource, brackish water has been extensively utilized in the industry. However, there are few cases of municipal potable water treatment plants that use low chloride content brackish water as the source. In this paper, the brackish water treatment efficiency of ultrafiltration (UF)/nanofiltration (NF) dual-membrane process was evaluated in a municipal potable water treatment plant, combining with a pilot optimization experiment. Results showed that UF guaranteed the inlet water quality of NF and NF could efficiently reject organics and salts, with a chloride removal over 95 %. Pilot experiment showed that the UF membrane flux decreased only 12 % after continuously 30-days operation under the optimized UF operation conditions, effectively extending the chemical cleaning interval. Response surface method was adopted in the NF removal efficiency and energy consumption optimization. With the increase of feed water conductivity, the influences of pressure and recovery on the removal efficiency were strengthened, and the removal efficiency could be regulated over a wider range. When the conductivity was less than 3500 μS/cm, NF could perform high treatment efficiency under the operation pressure of 0.65−0.85 MPa and recovery of 55–70 % . Besides, as feed conductivity increased, it was necessary to increase the pressure and reduce the recovery within this range to maintain efficient operation. This paper will provide a guidance for the UF/NF dual-membrane process design and operational optimization.

Activation of persulfate by biochar from spent malt rootlets for the degradation of trimethoprim in the presence of inorganic ions

AbstractBACKGROUNDAntibiotics such as trimethoprim (TMP) are used in large quantities and recent studies show that TMP is not eliminated completely in wastewater from municipal treatment plants. Advanced oxidation processes (AOPs), especially sulfate radical‐based AOPs, are highly reactive in the presence of a catalyst. Biochar, a green and low‐cost carbon material, is an excellent catalyst to degrade persistent pollutants. In this work, the degradation of TMP is studied using biochar from spent malt rootlets.RESULTSThe biochar has a specific surface area of 62 m2 g–1, point of zero charge 6.8, contains aromatics and is rich in –OH surface groups. The effect of sodium persulfate (SPS) (100–500 mg L–1), TMP (150–500 μg L–1), biochar (BC) concentration (45–180 mg L–1), solution pH (4–9) and water quality on degradation was investigated. The degradation rate increased with increasing SPS and BC concentration, decreasing TMP concentration and water matrix complexity, but remained insensitive to pH changes. Seven transformation products were identified and quantified, including hydroxylated and oxidized keto derivatives, and reaction pathways/mechanisms are proposed. The BC activation was coupled with low‐frequency ultrasound (20 kHz), which plays a synergistic role in degradation, but not when coupled with simulated solar irradiation.CONCLUSIONThe occurrence of various ions in bottle water (BW) impact negatively TMP degradation and so does the existence of organic matter in treated wastewaters. The studied reaction seems to be a surface process where the biochar serves as a platform to generate sulfate and –OH radicals, as well as an electron transfer mediator. © 2020 Society of Chemical Industry

Artificial neural network modelling of faecal coliform removal in an intermittent cycle extended aeration system-sequential batch reactor based wastewater treatment plant

Artificial neural network (ANN) models have been designed to predict faecal coliform and total coliform removal for an intermittent cycle extended aeration-sequential batch reactor (ICEAS-SBR). Wastewater influent pH, biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), oil & grease (O&G), total kjeldahl nitrogen (TKN), ammonical nitrogen (AN), total phosphorus (TP), faecal coliform, and total coliform were used to develop the network. The data used to train and test the network were obtained from the Jamnagar municipal corporation-waste water treatment plant (JMC-WWTP). Feedforward backpropagation algorithm with learngdm learning function was used to develop ANN models. The number of neurons in hidden layer were varied between 2–10 to find the most reliable network. The optimum ANN models were selected for faecal coliform and total coliform on trial-and-error method. The performance of designed models was tested by computing correlation coefficient, mean absolute deviation (MAD), root mean square error (RMSE), and mean absolute percentage error (MAPE). The network with 6 hidden neurons was optimum for faecal coliform, and 8 hidden neurons was optimum for total coliform. The produced simulation results were within 5 % of MAPE for both faecal and total coliform. The ANN models allow faecal coliform and total coliform levels in the treated wastewater effluent to be regulated that reduces the public and in particular the oyster consumer’s health risks.

Electro-oxidation of secondary effluents from various wastewater plants for the removal of acetaminophen and dissolved organic matter

Electro-oxidation of acetaminophen (ACT) in three different doped secondary effluents collected from a conventional Municipal Waste Water Treatment Plant (MWWTP), a MWWTP using a membrane bioreactor (WWTP MBR) and a lab-scale MBR treating source-separated urine (Urine MBR) was investigated by electro-Fenton (EF) coupled with anodic oxidation (AO) using sub-stoichiometric titanium oxide anode (Ti4O7). After 8 h of treatment, 90 ± 15%, 76 ± 3.8% and 46 ± 1.3% of total organic carbon removal was obtained for MWWTP, MWWTP-MBR and Urine-MBR respectively, at a current intensity of 250 mA, pH of 3 and [Fe2+] = 0.2 mM. Faster degradation of ACT was observed in the WWTP MBR because of the lower amount of competitive organic matter, however, >99% degradation of ACT was obtained after 20 min for all effluents. The acute toxicity of the treated effluent was measured using Microtox® tests. Results showed an initial increase in toxicity, which could be assigned to formation of more toxic by-products than parent compounds. From 3D excitation and emission matrix fluorescence (3DEEM), different reactivity was observed according to the nature of the organic matter. Particularly, an increase of low molecular weight organic compounds fluorescence was observed during Urine MBR treatment. This could be linked to the slow decrease of the acute toxicity during Urine MBR treatment and ascribed to the formation and recalcitrance of toxic organic nitrogen and chlorinated organic by-products. By comparison, the acute toxicity of other effluents decreased much more rapidly. Finally, energy consumption was calculated according to the objective to achieve (degradation, absence of toxicity, mineralization).

Understanding and Improving Microplastic Removal during Water Treatment: Impact of Coagulation and Flocculation.

The efficacy of plastic particle removal by municipal water treatment plants is currently uncertain, and the mechanisms involved in microplastic (MP) coagulation and flocculation have only been superficially investigated. The removal of pristine versus weathered plastic debris and the impact of plastic particle size on removal remain largely unexplored. In this study, coagulation, flocculation, and settling performances were investigated using pristine and weathered MPs (polyethylene (PE) and polystyrene (PS) microspheres, and polyester (PEST) fibers). Weathering processes that changed the surface chemistry and roughness of MPs impacted MP affinity for coagulants and flocculants. A quartz crystal microbalance with dissipation monitoring was used to identify the mechanisms involved during MP coagulation and flocculation. Measured deposition rates confirmed the relatively low affinity between plastic surfaces and aluminum-based coagulants compared to cationic polyacrylamide (PAM). In every case examined, coagulant efficiency increased when the plastic surface was weathered. Removals of 97 and 99% were measured for PEST and weathered PE, respectively. Larger pristine PE MPs were the most resistant to coagulation and flocculation, with 82% removal observed even under enhanced coagulation conditions. By understanding the interaction mechanisms, the removal of weathered MPs was optimized. Finally, this study explored the use of settled water turbidity as a possible indicator of MP removal.