Urban Wastewater Treatment Plants Research Articles

Enhancing Microplastics Recovery from Complex Sludge Samples Using COD-Guided Pretreatment

Given the society’s continuous reliance on plastic materials, large amounts of micron-sized plastic particles (i.e., microplastics, MPs) reach wastewater treatment plants (WWTPs) every day. Despite their effective removal from influent wastewater, over 90% of MPs in WWTPs are accumulated in sludge. Yet, there is no universally accepted method for quantifying and identifying MPs, obscuring our understanding of this pollution’s extent. Therefore, this study aims to develop a chemical oxygen demand (COD) based repeatable method for MPs analysis in sludge, which is a very complex, MPs-laden by product of WWTPs. The developed method is unique in that it removes the organic substances interfering with polymer analysis by monitoring the COD of sludge. Upon 90% of organic matter removal, MPs are extracted from the medium by a two-step density-based separation, sieved, stained with Nile Red, and counted using fluorescence microscopy. Moreover, quality assurance and quality control strategies including blank preparation and spike-and-recovery test procedures are followed. The protocol ensures a minimum 80% recovery rate of various MPs from both waste activated sludge (WAS) and wastewater samples, aligning with recommended standards. Crucially, the method preserves the chemical identity of MPs. Application of the protocol revealed that urban WWTP WAS had 475 MPs/g TS; industrial influent and effluents wastewater had 73 and 26 MPs/L; and industrial secondary and dewatered sludge had 114 and 132 MPs/g TS, consistent with the literature. This demonstrates the method’s robustness by revealing MPs reduction within the WWTP process and sludge accumulation as treatment progresses.Graphical

A novel membrane-based process to concentrate nutrients from sidestreams of an Urban Wastewater Treatment Plant through captured carbon dioxide from biogas

Among the challenges that wastewater treatment plants face in the path towards sustainability, reducing CO2 emissions and decrease the amount of waste highlight. Within these wastes, those that can cause eutrophication, such as nutrients (nitrogen and phosphorous) are of great concern. Herein we study a novel process to concentrate nutrients via membrane technology. In particular, we propose the use of forward osmosis, applying the carbonated solvent which contains the CO2 captured from the biogas stream as draw solution. This carbonated solvent has a high potential osmotic pressure, which can be used in forward osmosis to concentrate the nutrients stream. To this end, we present the results of an experimental plan specifically designed and performed to evaluate two main parameters: (1) nutrients concentration; and (2) water recovery. The process designed involves pH adjustment, membrane filtration to separate solids, pH reduction and forward osmosis concentration of nutrients. With this process, concentrations factor for nutrients in between 2 and 2.5 and water recovery of approximately 50 % with water flux of 7 to 8 L/(m2h) can be achieved.

Emerging Contaminants in the Effluent of Wastewater Should Be Regulated: Which and to What Extent?

Effluent discharged from urban wastewater treatment plants (WWTPs) is a major source of emerging contaminants (ECs) requiring effective regulation. To this end, we collected discharge datasets of pharmaceuticals (PHACs) and endocrine-disrupting chemicals (EDCs), representing two primary categories of ECs, from Chinese WWTP effluent from 2012 to 2022 to establish an exposure database. Moreover, high-risk ECs’ long-term water quality criteria (LWQC) were derived using the species sensitivity distribution (SSD) method. A total of 140 ECs (124 PHACs and 16 EDCs) were identified, with concentrations ranging from N.D. (not detected) to 706 μg/L. Most data were concentrated in coastal regions and Gansu, with high ecological risk observed in Gansu, Hebei, Shandong, Guangdong, and Hong Kong. Using the assessment factor (AF) method, 18 high-risk ECs requiring regulation were identified. However, only three of them, namely carbamazepine, ibuprofen, and bisphenol-A, met the derivation requirements of the SSD method. The LWQC for these three ECs were determined as 96.4, 1010, and 288 ng/L, respectively. Exposure data for carbamazepine and bisphenol-A surpassed their derived LWQC, indicating a need for heightened attention to these contaminants. This study elucidates the occurrence and risks of ECs in Chinese WWTPs and provides theoretical and data foundations for EC management in urban sewage facilities.

The potential for water recovery from urban waste water - The perspective of urban waste water treatment plant operators in Poland

Water recovery from waste water has become an essential element of the circular economy in the Baltic Sea region. However, there is little data on the possibility of using water recovered from urban waste water. A survey was conducted to learn the opinions of Poland waste water treatment plant operators. They were asked whether they recovered water for internal or external needs. Respondents indicated opportunities and barriers in this activity. The opinions of 107 operators show that work is underway on closing internal circuits in urban WWTPs. These solutions are technically relatively easy to implement and show measurable benefits (i.e., saving drinking water). However, water recovery for external purposes is rare and is at a very early stage. Despite this, the potential is significant, although many financial, organizational, technical, and mental barriers exist. The most critical challenge is the safe use of reclaimed water and the cost-effectiveness of the solutions. The survey also shows a need for education and involvement of the public.

The proliferation of antibiotic resistance genes (ARGs) and microbial communities in industrial wastewater treatment plant treating N,N-dimethylformamide (DMF) by AAO process.

The excessive use of antibiotics has resulted in the contamination of the environment with antibiotic resistance genes (ARGs), posing a significant threat to public health. Wastewater treatment plants (WWTPs) are known to be reservoirs of ARGs and considered to be hotspots for horizontal gene transfer (HGT) between bacterial communities. However, most studies focused on the distribution and dissemination of ARGs in hospital and urban WWTPs, and little is known about their fate in industrial WWTPs. In this study, collected the 15 wastewater samples containing N,N-dimethylformamide (DMF) from five stages of the anaerobic anoxic aerobic (AAO) process in an industrial WWTPs. The findings revealed a stepwise decrease in DMF and chemical oxygen demand (COD) content with the progression of treatment. However, the number and abundances of ARGs increase in the effluents of biological treatments. Furthermore, the residues of DMF and the treatment process altered the structure of the bacterial community. The correlation analysis indicated that the shift in bacterial community structures might be the main driver for the dynamics change of ARGs. Interestingly, observed that the AAO process may acted as a microbial source and increased the total abundance of ARGs instead of attenuating it. Additionally, found that non-pathogenic bacteria had higher ARGs abundance than pathogenic bacteria in effluents. The study provides insights into the microbial community structure and the mechanisms that drive the variation in ARGs abundance in industrial WWTPs.

Using the fish plasma model to evaluate potential effects of pharmaceuticals in effluent from a large urban wastewater treatment plant

Several pharmaceuticals and personal care products (PPCPs) were evaluated using the fish plasma model (FPM) for juvenile Chinook salmon exposed to effluent from a large urban wastewater treatment plant. The FPM compares fish plasma concentrations to therapeutic values determined in human plasma as an indication of potential adverse effects. We used human Cmax values, which are the maximum plasma concentration for a minimum therapeutic dose. Observed and predicted plasma concentrations from juvenile Chinook salmon exposed to a dilution series of whole wastewater effluent were compared to 1%Cmax values to determine Response Ratios (RR) ([plasma]/1%Cmax) for assessment of possible adverse effects. Several PPCPs were found to approach or exceed an RR of 1, indicating potential effects in fish. We also predicted plasma concentrations from measured water concentrations and determined that several of the values were close to or below the analytical reporting limit (RL) indicating potential plasma concentrations for a large number of PPCPs that were below detection. Additionally, the 1%Cmax was less than the RL for several analytes, which could impede predictions of possible effect concentrations. A comparison of observed and predicted plasma concentrations found that observed values were frequently much higher than values predicted with water concentrations, especially for low log10Dow compounds. The observed versus predicted values using the human volume of distribution (Vd), were generally much closer in agreement. These data appear to support the selection of whole-body concentrations to predict plasma values, which relies more on estimating simple partitioning within the fish instead of uptake via water. Overall, these observations highlight the frequently underestimated predicted plasma concentrations and potential to cause adverse effects in fish. Using measured plasma concentrations or predicted values from whole-body concentrations along with improved prediction models and reductions in analytical detection limits will foster more accurate risk assessments of pharmaceutical exposure for fish.

Defining Best Available Technique Performances for Urban Wastewater Plants: A French Application

The treatment of wastewater (WW) and the resulting sludge in urban WW treatment plants (UWWTPs) is accompanied by a significant consumption of resources as well as the concomitant emission of pollutants into the environment. One of the objectives of the NEXT (next generation of wastewater treatment plants) project is to identify sufficiently long-term optimization opportunities for processes to be selected as best available techniques (BATs) within the meaning of the industrial emissions directive (IED). The methodological framework used in this article is based on multi-criteria statistical tools, processing data from industrial plants to classify the sites studied and identify the reference plants in order to propose BAT references and associated emission levels that are reachable. Two public databases available on the internet were used, and 1,010 plants served as samples. The application and results demonstrated the applicability of the methodology and validated the mathematical approach used, as the thresholds comply with current French and European regulations. In the framework of the analysis conducted, five techniques (membrane bioreactor, bacterial bed, sand filter, and high-load or medium-load activated sludge) were identified as BAT according to the range of regulatory classification requirements for WW treatment plants (WWTPs). In addition, an example of reference values that may constitute a possible basis for the regulatory thresholds has been proposed. In parallel, a few discussion points were identified, including the choice of the metric for the reference values, the lack of data for the sludge line limiting identification of the BATs to the water line alone, the approximate characterization in the databases of certain parameters, as well as the problem of technique coupling due to the identification of one main technique.

Pilot plant approach combining photocatalysis and adsorption for antibiotics removal from slaughterhouse and urban wastewater treatment plant effluents

The main objective of this research is to perform a real case-study of antibiotic decontamination from real slaughterhouse and wastewater effluents by applying a sequential treatment of TiO2/UV–vis photocatalysis and adsorption. More precisely, the removal of five classes of antibiotics: enrofloxacin, sulfadiazine, trimethoprim, azithromycin, amoxicillin and amoxicillin degradation products was studied in an 80 L/h photocatalytic and adsorption pilot-scale plant over multiple cycles, operating in semi-continuous mode. The results exhibited significant removal rates, ranging from 77% to 100% for the slaughterhouse effluent, and 61–89% for the wastewater treatment plant effluent, thus demonstrating that the treatment is more effective when it is applied directly in the emission source, previous to antibiotic dilution in the municipal collector. Using the two processes sequentially results in greater efficiency than when they are used in isolation. After photocatalysis, antibiotic degradation products are easily adsorbed, since they have more affinity for the adsorbent, and the presence of competing compounds decreases considerably. After applying several cycles of treatment, the adsorption performance remains almost constant. By contrast, the photocatalysis performance decreased, which was attributed to catalyst agglomeration determined by Asymmetric Flow Field-Flow Fractionation (AF4) coupled with Dynamic Light Scattering (DLS) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS).

Forest waste composting-operational management, environmental impacts, and application.

In Portugal, the number of fires and the size of burnt areas are rising dramatically every year, increasing with improper management of agroforestry wastes (AFRs). This work aims to study the composting of these wastes with minimal operational costs and understand the environmental impact and the compost application on burnt soil. Thus, a study of life cycle assessment (LCA) was carried out based on windrow composting processes, considering the avoided environmental impacts associated with the end-product quality and its application as an organic amendment. Three composting piles were made with AFRs from the Residual Biomass Collection Centre (RBCC) in Bodiosa (Portugal). Sewage sludges (SS) from an urban wastewater treatment plant were used as conditioning agent. One pile with AFRs (MC) and another with AFRs and SS (MCS) were managed according to good composting practices. Another pile with the AFRs was developed without management (NMC), thus with a minimal operational cost. Periodically, it was measured several physical and chemical parameters according to standard methodologies. Eleven environmental impacts of compost production, MC and MCS, were analyzed by a LCA tool, and their effect on the growth of Pinus pinea was evaluated, using peat as reference. Composting evolution was expected for both piles. Final composts, MC and MCS, were similar, complying with organic amendment quality parameters. Compost NMC, with no operational management, showed the highest germination index. Piles MC and MCS showed similar environmental impacts, contributing to a negative impact on global warming, acidification, and eutrophication. Greater growth was obtained with application of MCS, followed by MC, and finally, peat. Composting is a sustainable way to valorize AFRs wastes, producing compost that could restore burnt soils and promote plant growth and circular economy.

Occurrence and distribution of azole antifungal agents in eight urban Romanian waste water treatment plants

Azole compounds are utilized to combat fungal infections in plants to protect them and also used for treating mycosis in humans. The LC-MS/MS method is a technique that combines liquid chromatography with tandem mass spectrometry for analysis of twelve azole compounds from wastewater (influent, effluent) and sewage sludge. The compounds were isolated from waste water using automatic extraction in the solid phase. Sludge samples were dried by lyophilization, after which they were subjected to ultrasound extraction with methanol. The quantification limits ranged from 0.3 ng/L (clotrimazole-CLO and prochloraz-PRO) to 1.5 ng/L (tetraconazole-TEB and penconazole-PEN), for wastewater samples and for sewage sludge, the LOQs ranged from 0.1 ng/g to 0.6 ng/g. High concentrations of climbazole-CLI (207–391 ng/L), tebuconazole (92–424 ng/L), and clotrimazole (6.9–93-ng/L) were observed in influent samples of the 8 urban wastewater treatment plants, followed by fluconazole (49.3–76.8 ng/L), and prochloraz (7.3–72 ng/L). The ∑Azoles had a maximum of 676 ng/L in the Galati effluent, followed by the Bucharest station 357 ng/L, and 345 ng/L in the Braila effluent. The highest value of the daily mass loading (input) level was observed for climbazole, 265 mg/day/1000 in Iasi station, followed by tebuconazole, 238 mg/day/1000 people in the Bucharest station, and 203 mg/day/1000 people for climbazole in the Targoviste station. The daily mass emission presented values between 0.7 and 247 mg/day/1000 people. The highest emissions were observed for climbazole, 247 mg/day/1000 people in Braila station; 174 mg/day/1000 people in the Iasi station and 129 mg/day/1000 people in the Bucharest station. The concentrations of climbazole detected in the effluent can present a high risk for the plants Lemna minor and Navicula pelliculosa. Clotrimazole may present a high risk to the plant Desmodesmus subspicatus and to the invertebrate Daphnia magna. PRO may present high risk to the invertebrate Mysidopsis Bahia.

EFFICIENCY OF AN UPFLOW ANAEROBIC FILTER FOR POULTRY EFFLUENT TREATMENT

Poultry slaughterhouses discharge large quantities of effluents that can be treated biologically. The objective of this study was to evaluate the chemical oxygen demand (COD) removal efficiency of an upflow anaerobic filter (UAF) with effluents from a poultry slaughterhouse, using volcanic stone (tezontle) as a support medium. Effluent characterization was carried out in accordance with Mexican official standards and standard methods. The support medium was inoculated with activated sludge from an urban wastewater treatment plant. The filter was operated in continuous flow with applied volumetric loads (AVL) of 1, 1.5, 2, 2.5, and 3 kg COD m-3 d-1 and hydraulic retention times (HRT) of 5.8, 3.8, 2.9, 2.3, and 1.9 days. An analysis of variance (ANOVA) was performed, and significant differences were determined for each AVL using the Krustall-Wallis method. The results obtained in the gradually applied AVL were 26.1, 53.2, 40.1, 17, and 49.7 % COD removal. However, in the AVL of 2 and 2.5 kg COD m-3 d-1, there was a decrease in the removal, which is attributed to the destabilization of the system due to the increase in loads. The maximum methane production was 125 mL at an AVL of 3 kg COD m-3 d-1, with a methane yield (YCH4) of 0.082 LCH4 g-1 COD-1rem. With no increase in methane production at each AVL, the theoretical yield of 0.328 LCH4 g-1 COD-1rem. was not met. The upflow anaerobic filter demonstrated its efficiency with a poultry effluent, with maximum COD removal greater than 50 %; however, more acclimatization time is required for the formation of biofilm in the support medium, a pretreatment that removes the high organic load and allows for gradual biogas production.  

Wastewater-based epidemiology applied at the building-level reveals distinct virome profiles based on the age of the contributing individuals

BackgroundHuman viruses released into the environment can be detected and characterized in wastewater. The study of wastewater virome offers a consolidated perspective on the circulation of viruses within a population. Because the occurrence and severity of viral infections can vary across a person’s lifetime, studying the virome in wastewater samples contributed by various demographic segments can provide valuable insights into the prevalence of viral infections within these segments. In our study, targeted enrichment sequencing was employed to characterize the human virome in wastewater at a building-level scale. This was accomplished through passive sampling of wastewater in schools, university settings, and nursing homes in two cities in Catalonia. Additionally, sewage from a large urban wastewater treatment plant was analysed to serve as a reference for examining the collective excreted human virome.ResultsThe virome obtained from influent wastewater treatment plant samples showcased the combined viral presence from individuals of varying ages, with astroviruses and human bocaviruses being the most prevalent, followed by human adenoviruses, polyomaviruses, and papillomaviruses. Significant variations in the viral profiles were observed among the different types of buildings studied. Mamastrovirus 1 was predominant in school samples, salivirus and human polyomaviruses JC and BK in the university settings while nursing homes showed a more balanced distribution of viral families presenting papillomavirus and picornaviruses and, interestingly, some viruses linked to immunosuppression.ConclusionsThis study shows the utility of building-level wastewater-based epidemiology as an effective tool for monitoring the presence of viruses circulating within specific age groups. It provides valuable insights for public health monitoring and epidemiological studies.

Ecological features of trace elements tolerant microbes isolated from sewage sludge of urban wastewater treatment plant

Worldwide wastewater treatment plants generate enormous amounts of sewage sludge, and their further disposal depends on the treatment technologies applied and spontaneously occurring microbiological processes. From different ages urban sewage sludge, 12 strains of bacteria with simultaneous tolerance to two or more trace elements: Co, Ni, Cu, Zn, Cd and Pb at concentration of 3-5 mmol were isolated and identified by PCR of target genes and Sanger sequencing methods. The isloated metal(loids) tolerant strains belong to the species, i.e., Serratia fonticola, Rhodococcus qingshengii, Pseudomonas fragi, Pseudomonas extremaustralis, Pseudomonas cedrina, Stenotrophomonas maltophilia, Serratia liquefaciens and Citrobacter freundii. The ecological features of the isolated strains were studied. The optimal growth temperatures for most strains was 15–30°C at pH range of 5–9, although some strains grew at 7°C (Pseudomonas fragi SS0-4, Serratia fonticola SS0-9 and Serratia fonticola SS12-11). Satisfactory growth of two strains (Serratia fonticola SS0-1and Citrobacter freundii SS60-12) was noted in an acidic medium at pH 4. Most of the strains grew in the NaCl concentration range of 1–5%. The isolated bacteria resistant to high concentrations of trace elements can be used for the effective mineralization of sewage sludge and for the decontamination of wastewater.

A thorough analysis of the occurrence, removal and environmental risks of organic micropollutants in a full-scale hybrid membrane bioreactor fed by hospital wastewater

The Urban Wastewater Treatment Directive recent draft issued last October 2022 pays attention to contaminants of emerging concern including organic micropollutants (OMPs) and requires the removal of some of them at large urban wastewater treatment plants (WWTPs) calling for their upgrading. Many investigations to date have reported the occurrence of a vast group of OMPs in the influent and many technologies have been tested for their removal at a lab- or pilot-scale. Moreover, it is well-known that hospital wastewater (HWW) contains specific OMPs at high concentration and therefore its management and treatment deserves attention. In this study, a 1-year investigation was carried out at a full-scale membrane bioreactor (MBR) treating mainly HWW. To promote the removal of OMPs, powdered activated carbon (PAC) was added to the bioreactor at 0.1 g/L and 0.2 g/L which resulted in the MBR operating as a hybrid MBR. Its performance was tested for 232 target and 90 non-target OMPs, analyzed by UHPLC-QTOF-MS using a direct injection method. A new methodology was defined to select the key compounds in order to evaluate the performance of the treatments. It was based on their frequency, occurrence, persistence to removal, bioaccumulation and toxicity. Finally, an environmental risk assessment of the OMP residues was conducted by means of the risk quotient approach. The results indicate that PAC addition increased the removal of most of the key OMPs (e.g., sulfamethoxazole, diclofenac, lidocaine) and OMP classes (e.g., antibiotics, psychiatric drugs and stimulants) with the highest loads in the WWTP influent. The hybrid MBR also reduced the risk in the receiving water as the PAC dosage increased mainly for spiramycin, lorazepam, oleandomycin. Finally, uncertainties and issues related to the investigation being carried out at full-scale under real conditions are discussed.

Evaluation of physical and chemical characteristics of wastewater and sludge of Zahedan urban wastewater treatment plant for reuse

Following the water shortage in the world, the use of wastewater as a sustainable resource has been considered in large volume. The study conducted to evaluate the physical and chemical characteristics of the wastewater and sludge of the Zahedan urban wastewater treatment plant showed that the wastewater and sludge treatment system of the treatment plant has high efficiency and effectiveness in removing the investigated parameters. The investigated parameters in the effluent included Chemical oxygen demand (COD), Biochemical oxygen demand (BOD), and Total suspended solids (TSS), turbidity, temperature, nitrate, nitrite, phosphate, pH, zinc, cobalt, lead and copper. Also, the investigated parameters in the sludge included Mixed liquor suspended solids (MLSS), Mixed liquor volatile suspended solids (MLVSS), pH, electrical conductivity and heavy metals. The results showed that the average concentration of metals in the treated effluent is Zn > Mn > Cu > Pb > Ni > Cr > Cd ،and Chemical oxygen demand and Biochemical oxygen demand in the effluent of this treatment plant are on average 171 and 44.4 mg/L, respectively, and its discharge in surface water is limited, but it can be applied for agriculture. Also, the purified sludge had the necessary standards and could be used as soil or household fertilizer and compost for agricultural land.

A Battery of Simple Bioassays for Domestic and Industrial Wastewater Treatment Plants in Konya, Turkey

Wastewater ingredients present risks to the environment and can cause health problems. The aim of this study was to identify the toxicological effects of influent and effluent wastewater from Konya Urban Wastewater Treatment Plant (KU WWTP) and Konya Organized Industrial Zone Wastewater Treatment Plant (KOI WWTP). Three different trophic level toxicity tests were conducted to determine the possible harmful effects of wastewater on the environment. The base toxic unit values of the Lepidium sativum toxicity test for the inlet and outlet samples of KU WWTP were found to be 1.43 and 1.10, respectively. Both values classified the analyzed wastewater into the “toxic” category. Wastewater entering the KU wastewater treatment facility was classified as “toxic” for the presence of toxic substances according to the Vibrio fischeri toxicity testing. Influent samples from the KOI wastewater treatment plant were classified as “toxic” with the Vibrio fischeri toxicity test. In addition, based on the fish bioassay value (TDF), wastewater from the KOI treatment facility was also classified as “toxic”. It was concluded that increased chemical oxygen demand and concentrations of total nitrogen and phosphorus and of certain heavy metals above the limits played a decisive role in classifying the samples as “toxic”. The results of this study suggest that all three tests have the potential to assess wastewater toxicity and that changes in wastewater properties may result in differences in test sensitivity.

Unveiling the Microbiome Landscape: A Metagenomic Study of Bacterial Diversity, Antibiotic Resistance, and Virulence Factors in the Sediments of the River Ganga, India.

The global rise in antibiotic resistance, fueled by indiscriminate antibiotic usage in medicine, aquaculture, agriculture, and the food industry, presents a significant public health challenge. Urban wastewater and sewage treatment plants have become key sources of antibiotic resistance proliferation. The present study focuses on the river Ganges in India, which is heavily impacted by human activities and serves as a potential hotspot for the spread of antibiotic resistance. We conducted a metagenomic analysis of sediment samples from six distinct locations along the river to assess the prevalence and diversity of antibiotic resistance genes (ARGs) within the microbial ecosystem. The metagenomic analysis revealed the predominance of Proteobacteria across regions of the river Ganges. The antimicrobial resistance (AMR) genes and virulence factors were determined by various databases. In addition to this, KEGG and COG analysis revealed important pathways related to AMR. The outcomes highlight noticeable regional differences in the prevalence of AMR genes. The findings suggest that enhancing health and sanitation infrastructure could play a crucial role in mitigating the global impact of AMR. This research contributes vital insights into the environmental aspects of antibiotic resistance, highlighting the importance of targeted public health interventions in the fight against AMR.

The Aquatic Environment and Pharmaceutical Products- A Review

In recent decades, more and more pharmaceutical products exist in the nature. In many parts of the Globe, and especially close to urban areas, medicines have been presented in surface waters, groundwaters and soils. This is related to the growth in the utilisation of medicine and the development of analytical detection techniques in order determination of these traces of compounds in the environment. Pharmaceuticals reach the nature through the discharge of effluents from urban waste water treatment plants, the discharge of effluents from hospitals and drug factories, the using of sewage sludge in agriculture, the breeding of herbivorous animals, the treatment of pets, the spreading of manure and aquaculture, the improper disposal in landfills of unused pharmaceutical substances and contaminated waste. Researches showed that pharmaceutical products and residues are mainly present in water bodies and that they are partly eliminated by conventional wastewater treatment plants, which currently cannot effectively filter all pharmaceuticals.

Modeling Indirect Greenhouse Gas Emissions Sources from Urban Wastewater Treatment Plants: Integrating Machine Learning Models to Compensate for Sparse Parameters with Abundant Observations.

Electricity consumption and sludge yield (SY) are important indirect greenhouse gas (GHG) emission sources in wastewater treatment plants (WWTPs). Predicting these byproducts is crucial for tailoring technology-related policy decisions. However, it challenges balancing mass balance models and mechanistic models that respectively have limited intervariable nexus representation and excessive requirements on operational parameters. Herein, we propose integrating two machine learning models, namely, gradient boosting tree (GBT) and deep learning (DL), to precisely pointwise model electricity consumption intensity (ECI) and SY for WWTPs in China. Results indicate that GBT and DL are capable of mining massive data to compensate for the lack of available parameters, providing a comprehensive modeling focusing on operation conditions and designed parameters, respectively. The proposed model reveals that lower ECI and SY were associated with higher treated wastewater volumes, more lenient effluent standards, and newer equipment. Moreover, ECI and SY showed different patterns when influent biochemical oxygen demand is above or below 100 mg/L in the anaerobic-anoxic-oxic process. Therefore, managing ECI and SY requires quantifying the coupling relationships between biochemical reactions instead of isolating each variable. Furthermore, the proposed models demonstrate potential economic-related inequalities resulting from synergizing water pollution and GHG emissions management.

Utilization of Microalgae for Urban Wastewater Treatment and Valorization of Treated Wastewater and Biomass for Biofertilizer Applications

Rapid urbanization has substantially increased freshwater consumption and consequent wastewater generation. The produced wastewater is an abundant resource of phosphorus, nitrogen, and organics. Currently, well-established activated sludge processes are utilized in conventional wastewater treatment plants to remove organics. However, removing nitrogenous and phosphorus compounds continues to be challenging and energy-intensive for urban wastewater treatment plants. Therefore, the current study aims to understand how photosynthetic microalgae can recover phosphorus and nitrogen from urban wastewater and how wastewater-grown microalgae biomass may be used as a biofertilizer and biostimulant. Utilizing microalgae biomass treated with urban wastewater as a biofertilizer promotes plant growth in a manner similar to other organic manures and conventional fertilizers while minimizing nutrient loss to the soil. Furthermore, the microalgal recovery of nutrients from urban wastewater could have potential energy reductions of 47% and 240% for nitrogen and phosphorus, respectively. In addition to producing treated wastewater suitable for a variety of irrigation systems, microalgae biomass is a potential sustainable alternative resource that could reduce conventional inorganic fertilizer usage.