Typical Wastewater Treatment Plants Research Articles

Fate of household and personal care chemicals in typical urban wastewater treatment plants indicate different seasonal patterns and removal mechanisms

Studies on the presence and fate of household and personal care chemicals (HPCCs) in wastewater treatment plants (WWTPs) are important due to their increasing consumption worldwide. The seasonal patterns and removal mechanisms of HPCCs are not well understood for WWTPs that apply different treatment technologies. To answer these questions, the sewage and sludge samples were taken from 10 typical WWTPs in Northeast China. Levels of UV filters in the influents in the warm season were significantly greater than that of the cold season (p < 0.05). Significant seasonal differences were found for the removals of many HPCCs. Results revealed that the highest removal efficiencies were found for linear alkylbenzene sulphonates with values ranging from 97.2% to 99.7%, and the values were 50.0%–99.9% for other HPCCs. The SimpleTreat model demonstrated that the studied WWTPs were operating with high efficiency at the time of sampling. The sorption of HPCCs to sludge can be strongly associated with their physicochemical parameters. Mass balance calculation suggested that sorption was the dominant mechanism for the removal of antimicrobials, while degradation and/or biotransformation were the other mechanisms for removing the most HPCCs in the WWTPs. This study real the factors influencing the seasonal patterns and removal mechanisms which imply the need for further studies to fully understands the plant and human health implications as sludge could be used in the municipal land application of biosolids.

Investigation of microplastic removal from greywater by coagulation and dissolved air flotation

Microplastics (MPs) have recently become a controversial issue, mainly due to their eco-toxicological effects on aquatic environments. Although a typical wastewater treatment plant (WWTP) removes a large number of MPs from the wastewaters, final effluents are yet considered to be the primary sources of MP contaminations into the environment. Hence, there should be a tertiary treatment called advanced wastewater treatment technology for efficient MP removal. In the current research, Al-based and Fe-based coagulants were used in a dissolved air flotation (DAF) cell as an advanced wastewater treatment technology to remove polyethylene (PE) MPs from greywater, which is one of the most predominant types of MPs found in the greywater. PE reduction up to 96.10 % and 70.56 % were observed for Al- and Fe-based coagulants, respectively. The operative parameters, including pressure, pH, coagulant dosage, and water flow rate into the flotation cell, were identified. The experimental design was developed using Design-Expert software to investigate and maximize the PE removal efficiency. As a result, some sufficiently accurate statistical models were proposed to obtain the optimum quantities of the respective factors. It was determined that the most effective removal was achieved with 5.95 bar saturation pressure, pH 6, 14.46 mg/L coagulant concentration, and 680.5 mL/min water flow rate into the flotation cell using AlCl3·6H2O as the coagulant.

Influence of wastewater treatment process on pollution characteristics and fate of microplastics

The increasing abundance of microplastics (MPs) in rivers and oceans continues to face major challenges. In particular, MPs with smaller particle sizes are difficult to identify and quantify when they reach the environment. This study investigated four typical wastewater treatment plants (WWTPs), including urban WWTPs and industrial WWTP with different treatment technologies. The results showed that the average abundance of MPs in the influent and effluent was 538.67 ± 22.05 n/L to 1290 ± 65.26 n/L and 20.44 ± 1.19 n/L to 40.67 ± 11.12 n/L. The primary and secondary treatment processes can effectively remove MPs between 51.04% and 72.82% from wastewater. After tertiary treatments, the removal efficiency was further increased to more than 90%. The study aims to explore the removal mechanism of MPs in each stage of the wastewater treatment process and to reveal the fate of MPs in WWTPs, and help to understand their future monitoring to optimize the wastewater treatment process.

Technology and Concept of Wastewater Treatment: Differences Between the Rhine Basin and the Yangtze Basin

Based on field visits and literature research, the situations of several typical wastewater treatment plants (WWTPs) in the Rhine basin and the Yangtze basin were investigated, to compare the technology and concept of wastewater treatment in these two areas. Our results showed that WWTPs in the Rhine performed well in pollutant removal, and have shifted their focus to energy production and nutrient recovery; While in the Yangtze basin, most WWTPs still operate on the sole concept of pollution treatment. Though China's WWTPs attach importance to water reclamation, the related technologies are still under development. In years to come, the construction of New Concept WWTPs is expected by Chinese famous experts, to integrate sustainable wastewater treatment and energy/nutrient recovery. To better plan its future avenue in wastewater treatment, China is suggested to learn from the successful practice of energy production and nutrient recovery of WWTPs in the Rhine.

Fate processes of Parabens, Triclocarban and Triclosan during wastewater treatment: assessment via field measurements and model simulations.

The high levels of parabens (including methyl-, ethyl- and propyl congeners), triclocarban (TCC) and triclosan (TCS) used every year in China might be a problem to the typical wastewater treatment plant (WWTP). This study addresses measurements of parabens, TCC and TCS Northern China WWTP and a modelling assessment on the occurrence, fate and removal pathways in WWTP. Per-capita emissions of the three parabens, TCC and TCS to the WWTP were estimated as 0.41, 0.11 and 0.07mg/d. After the wastewater treatment processes, 94, 92 and 87% of parabens, TCC and TCS were removed. The major removal pathway of parabens was biodegradation while that of TCC and TCS were sorption to sludge. Computer simulations on the fate processes of parabens, TCC and TCS in the WWTP using the SimpleTreat 4.0 model suggested the model could generally reproduce the measurements with root mean squared errors (RMSEs) of less than 10ng/L. However, the model underestimated the removal of TCC and TCS from water to sludge in the primary tank. These discrepancies were attributed to the uncertainty of the predicted organic carbon-water partition coefficients (Koc) to which the modelling results are highly sensitive. The model predictions using updated Koc became more accurate and RMSEs of TCC and TCS were reduced by 40 and 80%, respectively. The modelling assessment suggests that the SimpleTreat, as a generic model to simulate chemical fate processes in WWTPs, has the potential to be applied to other similar WWTPs in China for estimating environmental releases of parabens, TCC and TCS at a larger spatial scale.

Industrial Emission Characteristics and Control Countermeasures of VOCs in Chinese Rapid Economic Development Areas

With the rapid development of China's economy, volatile organic compounds (VOCs) as the precursor of smog and ozone are of increasing concern, especially in rapidly developing areas. This paper is a systematic analysis of VOCs emissions and distribution trends in 12 typical industrial sectors, garbage and wastewater treatment plants, comprehensive industrial parks, and residential districts in Beijing-Tianjin-Hebei, Yangtze River Delta, and Pearl River Delta Regions. The results show that pharmacy, rubber producing, as well as paint spraying are the top three industries among the 12 typical industries with the highest average VOCs emission concentrations at 541, 499, and 450 mg·m-3, respectively. By comparison, the average emission concentration of VOCs from the pharmaceutical industry in Yangtze River Delta and Beijing-Tianjin-Hebei Region was, respectively, about 112 and 1.00×103 mg·m-3. The paint spraying industry in the Pearl River Delta region has the highest emission rate with an average concentration of 1.04×103 mg·m-3. The investigation pertaining to the distribution of different VOCs categories indicates that highly toxic aromatics and halogenated hydrocarbons account for the highest emissions in paint spraying and pharmaceutical industries, reaching ratios of 55.99% and 26.57%, respectively. Additionally, among the three major economic zones, the VOCs concentration is the lowest in residential areas and comprehensive industrial parks in the Yangtze River Delta but the highest in the Beijing-Tianjin-Hebei Region, which is consistent with the distribution of industrial emissions in each region. Moreover, the research reveals that VOCs concentration in residential districts experienced a fluctuating reduction from 2002 to 2018. The significant reduction since 2016 suggests that formulated policies, laws and standards, along with the performed techniques have made significant contributions to the control of VOCs.

Fate of Household and Personal Care Chemicals (HPCCs) in Sewage and Sludge from Typical Urban Wastewater Treatment Plants

Fate of Household and Personal Care Chemicals (HPCCs) in Sewage and Sludge from Typical Urban Wastewater Treatment Plants

A journey of wastewater to clean hydrogen: A perspective

A journey of wastewater to clean hydrogen: A perspective

A framework for P-cycle assessment in wastewater treatment plants

Phosphorus (P) in wastewater has a variety of negative effects and is usually permanently lost as a non-renewable resource. To mitigate future P shortage, P must be recovered from wastewater, preferably by bio-based technologies to avoid toxic side streams. A standardized procedure for the determination of P types and P concentrations in all liquid and solid process stages was established, which is applicable to all full-scale wastewater treatment plants (WWTPs). Based on this, an equally universal calculation framework for P-cycle assessment based on volume flow and mass load rates was designed to identify the most promising process streams for biological P recovery. As an example, in 16 process streams of a typical WWTP, concentrations of free, bound and total P were calculated and microbial communities were analyzed by flow cytometry over 748 days. The most promising process streams for the recovery of free P were anaerobic digester sludge, centrate and the water-extracts of the biosolids with 0.510 kg P m−3, 0.075 kg P m−3 and 1.023 kg P m−3, while the best process streams for the recovery of bound P were return sludge, excess sludge, anaerobic digester sludge, and the solids of the biosolids with 0.300 kg P m−3, 0.268 kg P m−3, 0.213 kg P m−3 and 1.336 kg P m−3, respectively. Microorganisms capable of P accumulation were active in all process stages and it was observed that chemical P precipitation antagonizes biological P removal. The framework for P-cycle assessment was able to identify process streams that are economically viable to make future in-stream technologies for biological P removal feasible.

Optimization of electro-Fenton oxidation of carbonated soft drink industry wastewater using response surface methodology

The immense volume of highly polluted organic wastewater continuously generated in the beverage industry urges the design of new types of wastewater treatment plants. This study aimed to evaluate the applicability of the electro-Fenton (EF) technique to reduce organic pollution of real effluent from a carbonated soft drink factory. The impact of various process variables like pH, time, current density, H2O2/Fe2+ molar ratio, and the volume ratio of H2O2/soft drink wastewater (SDW) was analyzed using response surface methodology (RSM). The observed responses were in good agreement with predicted values obtained through optimization. The optimum conditions showed a chemical oxygen demand (COD) removal efficiency of 73.07 %, pH of 4.14, time of 41.55 min, current density of 46.12 mA/cm2, H2O2/Fe2+ molar ratio of 0.9802, and H2O2/SDW volume fraction of 2.74 ml/l. The EF process was able to effectively diminish the organic pollution, reduce the residence time and, therefore, the operating costs.

Distribution and diversity of filamentous bacteria in wastewater treatment plants exhibiting foaming of Taihu Lake Basin, China

Foaming caused by filamentous bacteria in activated sludge (AS) is a common phenomenon in municipal wastewater treatment plants (WWTPs) in Taihu Lake Basin of South China. In this study, total bacterial and filamentous bacterial communities were comprehensively characterized in AS and foams from eight municipal WWTPs by high-throughput sequencing technology. Results showed that alpha diversities of total bacterial communities in foams were obviously lower than those in AS samples. The bacterial community structures were significantly different between WWTPs rather than sample types (AS vs. foam). For most WWTPs, the Actinobacteria phylum was highly enriched in foams and the most abundant genera in foams were common mycolata. Sixteen filamentous bacteria were identified against the improved bulking and foaming bacteria (BFB) database. Abundance and composition of BFB in different WWTPs and different sample types were significantly different. ‘Nostocoida limicola’ I Trichococcus and Microthrix were generally dominant in AS samples. The dominant BFB in foams were associated with Microthrix, Skermania, Gordonia, and Mycobacterium. A new Defluviicoccus spp. in cluster III was identified in severe and continuous foams. Moreover, dominant BFB in stable and continuous foams with light level in one typical WWTP were diverse, even, and dynamic. Bacterial co-occurrence network analysis implied that the bacterial community of AS was more sensitive to disturbance than that of foam.

Evaluation of Factors Influencing the Environmental Spread of Pathogens by Wastewater Treatment Plants

Wastewater treatment plants (WWTPs), usually designed to remove organic pollutants and nutrients, are often poorly equipped to handle pathogens. The present study investigated the multiple barriers provided by WWTPs to understand their role in spreading pathogenic bacteria into the environment. Three types of WWTPs (hospital, domestic, and mixed) differing in the source of raw influent, operating parameters, and reactor configuration (biological and tertiary treatment processes) were compared for the presence of fecal indicators and pathogenic bacteria discharged in their treated effluents. The plate-count technique was used for bacterial enumeration on selective agar. The microbial quality of the treated effluent was observed to be strongly influenced by characteristics inherent to a WWTP rather than depending on the characteristics of the raw influent. Among the different configurations studied, membrane bioreactor (MBR) treatment followed by chlorine disinfection provided an effluent of the highest quality (100% bacterial removal rates) followed by moving bed bioreactor (MBBR) combined with UV disinfection. MBR treatment greatly increased the efficiency of chlorine disinfection. Higher total suspended solids (TSS) removal corresponded to higher bacterial removal rates. Tertiary treatment proved to be an important determinant of the microbial quality of the final effluent. A great heterogeneity was observed in the removal rates of different bacterial groups with different treatment processes. The highest removal was observed in the case of indicators and least in the case of emerging pathogens like Escherichia coliO157: H7 indicating a lack of correlation between traditional indicators and emerging pathogens and also the inefficiency of the current wastewater treatment technologies in dealing with emerging pathogens.

New insights into the evaluation of anaerobic properties of sludge: Biodegradability and stabilization

Evaluating anaerobic biodegradability of sludge and then identifying the stabilization of digestate is necessary in sludge treatment and disposal. 48 sludge samples from 24 typical waste water treatment plants (WWTPs) in 11 provinces in China were selected to investigate the relationship between Biochemical Acidogenic Potential (BAP) test and Biochemical Methane Potential (BMP) test. The volatile fatty acid (VFA) production obtained from BAP tests was found linearly related to the ultimate methane production from corresponding BMP tests. Satisfying results were obtained with Pearson correlation coefficient as 0.929 and R2 value as 0.76. Furthermore, the physio-chemical characteristics (FCI, SUVA254, E4/E6) of supernatant, which were associated with humic-like substances (HS), were investigated before and after BMP tests. Through which a new criterion (FCI>1.50, SUVA254>1.10, E4/E6<4.0) was proposed to evaluate the stabilization level of anaerobic digested sludge.

Mass loading, distribution, and removal of antibiotics and antiretroviral drugs in selected wastewater treatment plants in Kenya

The discharge of active pharmaceutical ingredients (APIs) into the aquatic environment from wastewater effluents is a concern in many countries. Although many studies have been conducted to evaluate the APIs removal efficiencies and emissions to the environment in wastewater treatment plants (WWTPs), most of these studies considered the aqueous and sludge phases, disregarding the suspended particulate matter (SPM) phase. To try to understand the role of the SPM, the occurrence of five most common antibiotics and three antiretroviral drugs (ARVDs) commonly used in Kenya were investigated in this study. APIs partitioning and mass loading in influents and effluents of three different WWTPs: trickling filters, stabilization ponds, and decentralized fecal sludge system, were evaluated. API concentration levels ranging from ˂LOQ (limit of quantification) to 92 μgL−1 and ˂LOQ to 82.2 mgkg−1 were observed in aqueous samples and solid samples respectively, with SPM accounting for most of the higher concentrations. The use of the aqueous phase alone for determination of removal efficiencies showed underestimations of API removal as compared to when solid phases are also considered. Negative removal efficiencies were observed, depending on the compound and the type of WWTP. The negative removals were associated with deconjugation of metabolites, aggregated accumulation of APIs in the WWTPs, as well as unaccounted hydraulic retention time during sampling. Compound characteristics, environmental factors, and WWTPs operation influenced WWTPs removal efficiencies. Wastewater stabilization ponds had the poorest removals efficiencies with an average of −322%. High total mass loads into the WWTPs influent and effluent of 22,729 and 22,385 mg day−1 1000 PE−1 were observed respectively. The results aims at aiding scientists and engineers in planning and designing of WWTPs. Findings also aim at aiding policy-making on pharmaceutical drug use and recommend proper wastewater management practices to manage the high mass loading observed in the WWTPs.

Substituted diphenylamine antioxidants (SDPAs) in typical domestic wastewater treatment plants and Songhua River in the northeast of China

Limited studies focus on the occurrence, removal rate and seasonal variation of substituted diphenylamine antioxidants (SDPAs) in surface water and wastewater in China. In this paper, the detection method of SDPAs was established by the ultra-performance liquid chromatography-tandem mass spectrometry. Daily variations suggested that significant variations were found for the concentrations of some SDPAs in the influent. It was found that the SDPAs could be detected in all the effluent samples and C8/C8-DPA was the predominant compound in two WWTPs. The levels of most SDPAs in the effluent were much lower than that of influent, with the removal efficiencies of total SDPAs ranged from 57.9% to 84.2%. There were significant differences with the SDPA concentrations in the influent between different seasons. Higher concentrations of SDPAs were found at downstream than those of upstream. The results of this study provide more environmental occurrence data and new insights into the research on the environmental fate of these compounds.

Predicting the potential of sludge dewatering liquors to recover nutrients as struvite biominerals

Phosphorus and nutrient recovery from wastewater as mineral salts can support local replenishment of fertilisers and reduce mining, contributing to the circular economy. Wastewater and related streams are rich in nutrients, however; there is need to develop bio-based processes to recover them. This study investigates the fractions of phosphorus (P) used by Brevibacterium antiquum to form struvite biominerals (bio-struvite) in wastewater sludge dewatering liquors. After 72h of incubation, 25.6 mg P/L were recovered as bio-struvite from 12.4 mg P/L organic plus condensed P and 13.2 mg P/L of ortho-phosphate. The potential of sludge dewatering liquors to recover nutrients as struvite was investigated by characterising ten types of sludge liquors (originating from primary, secondary sludge, feed to anaerobic digester and digestate, from 3 types of wastewater treatment plants) for their P fractions together with other parameters relevant for B. antiquum growth. Results indicated that liquors obtained from primary sludge, feed to anaerobic digesters and digestate were the most suitable to produce bio-struvite, as these were found to frequently have a high content of organic and condensed P, between to 276–732 mg P/L. Liquors, from all the investigated sites, presented a higher potential for bio-struvite production than with conventional struvite precipitation. This study demonstrated that B. antiquum could convert organic and condensed P into bio-struvite, and this opens up a completely new way to recover forms of phosphorus that are not typically available for nutrient recovery in a single process.

Data-Driven Iterative Adaptive Critic Control Toward an Urban Wastewater Treatment Plant

The wastewater treatment is an important avenue of resources cyclic utilization when coping with the modern urban diseases. However, there always exist obvious nonlinearities and uncertainties within wastewater treatment systems, such that it is difficult to accomplish proper optimization objectives toward these complex unknown platforms. In this article, a data-driven iterative adaptive critic (IAC) strategy is developed to address the nonlinear optimal control problem. The iterative algorithm is constructed with a general framework, followed by convergence analysis and neural network implementation. Remarkably, the derived IAC control policy with an additional steady control input is also applied to a typical wastewater treatment plant, rendering that the dissolved oxygen concentration and the nitrate level are maintained at desired setting points. When compared with the incremental proportional-integral-derivative method, it is found that faster response and less oscillation can be obtained during the IAC control process.

Monitoring Organic Pollutants in Waters Using the Diffusive Gradients in the Thin Films Technique: Investigations on the Effects of Biofouling and Degradation.

The diffusive gradients in thin films (DGT) passive sampling technique has been increasingly used to provide time-weighted average concentrations of the biorelevant fraction of organic contaminants in waters, with high spatial and temporal resolutions at low cost. This study was tested for the effects of biofouling and compound degradation/loss during sample handling/storage on the DGT measurement of a range of emerging organic pollutants. Biofouling was tested using biofilms collected from the influent and effluent of a typical urban wastewater treatment plant. Most (85%) target compounds showed no detectable effect on the DGT measurement when 8- and 15-day biofouled membrane filters were used. Four storage methods were designed to test for within-sampler degradation/loss for up to 2 months. Intact samplers can be simply stored in polyethylene bags at ambient temperature (18-26 °C) with most compounds stable (mass loss <20%) for at least 1 week. Keeping intact samplers at 4 °C or binding gels in solvent gave good recoveries, with most chemicals being stable for up to 2 months, although the best results were obtained when binding gels were kept in solvent at 4 °C. Recommendations are made for sample handling and storage of DGT samplers used for determination of trace organics in monitoring and surveillance campaigns.

Comparison of fluorotelomer alcohol emissions from wastewater treatment plants into atmospheric and aquatic environments

Recent studies have revealed that wastewater treatment plants (WWTPs) are an important source of fluorotelomer alcohols (FTOHs) in the environment. However, it remains unclear whether volatilization to the atmosphere or discharge with wastewater effluent into receiving water bodies is the dominant pathway through which FTOHs enter the environment; it also remains unclear how the relative importance of these two emission pathways varies among seasons and homologs. Here, we estimated the emissions of 6:2 and 8:2 FTOHs through these two pathways from a typical WWTP in Beijing, China, by measuring height-dependent air concentrations above the wastewater surface; we also measured wastewater concentrations among the four annual seasons. Our results showed that atmospheric emissions dominate total annual FTOH emissions, but are not dominant in every single season. Emission to the aquatic environment is dominant during seasons with less wind (i.e., summer and fall). While the abundance of 6:2 FTOH has increased in recent years, 8:2 FTOH remains the major FTOH homolog released into the environment in China. This study provides comprehensive information regarding FTOH emissions from WWTPs to the environment and practical guidance for future monitoring practices.

Disinfection for decentralized wastewater reuse in rural areas through wetlands and solar driven onsite chlorination

Increasing water scarcity is of growing concern in Europe, especially in Mediterranean countries along coastlines. Wastewater reuse reduces water stress, but often requires the absence of pathogen indicators and the application of chlorine to assure residual disinfection. However, the effluent qualities of typical Wastewater Treatment Plants (WWTP) show immense chlorine demands. This makes the supply, handling and dosing of typical WWTP effluent challenging, especially in rural regions. In the work presented here, a vertical flow constructed wetland (VFCW) was combined with a small-scale solar-driven Onsite Chlorine Generation system (OCG) to further improve effluent qualities for different WWTPs and to produce chlorine stock solution directly at the site. To test different operational conditions the VFCW received WWTP effluent from a) an Activated Sludge and b) a High-Rate Algae Pond system. The VFCW reduced TSS by 92%, COD by 80%, and NH4 by over 99% and the chlorine demand by 85%. The log-unit reduction of the VFCW/OCG system reached ≥5.1 for total coliforms and ≥4.6 for E. Coli. During VFCW passage the already high electrical conductivity further increased to beyond permissible reuse limits due to high evapotranspiration (ET) rates of the planted vegetation Arundo donax. Unique aspects of this setup were that neither chemicals nor external electricity were required to run the system. The elevated chloride concentration of the treated WW (819 ± 132 mg/L) proved sufficient for the production of chlorine stock solution. However, the solar-driven OCG system tested here consumed considerably more electricity compared to other OCGs available on the market. Nevertheless, the system presented here may be considered an efficient disinfection alternative for decentralized WW reuse applications at remote sites with both limited access to grid electricity and strict requirements for pathogen indicators.