Typical Municipal Wastewater Treatment Plants Research Articles

Analyzing the variation of greenhouse gas emissions from typical municipal wastewater treatment plants in Beijing during 2007–2021

With the proposal of dual carbon goals and stringent effluent standards, the path of mitigating greenhouse gas (GHG) emissions from wastewater treatment plants (WWTPs) has gained significant research attention. Here, we evaluate the impact of season, elevated standards, operating parameters, and using clean energy on GHG emissions from 8 typical WWTPs in Beijing based on 180 monthly monitoring data. Coupled with the increasing demand for wastewater treatment and 77% more chemical oxygen demand being removed in 2017, total GHG emissions from 5 WWTPs increased by 89% compared to the status quo in 2007, and after energy structure reform total GHG emissions decreased by 17% in 2021. Scenario analysis reveals that energy recovery and clean energy utilization provide 64% and 48% mitigation potential by 2050, respectively. We argue stricter effluent standard leads to GHG emissions growth in WWTPs; meanwhile, process optimization, proper temperature and targeted policies at WWTPs can reduce GHG emissions.

Nutrient recovery from wastewater for hydroponic systems: A comparative analysis of fertilizer demand, recovery products, and supply potential of WWTPs

Nutrient recovery from wastewater treatment plants (WWTPs) for hydroponic cultivation holds promise for closing the nutrient loop and meeting rising food demands. However, most studies focus on solid products for soil-based agriculture, thus raising questions about their suitability for hydroponics. In this study, we address these questions by performing the first in-depth assessment of the extent to which state-of-the-art nutrient recovery processes can generate useful products for hydroponic application. Our results indicate that less than 11.5% of the required nutrients for crops grown hydroponically can currently be recovered. Potassium nitrate (KNO3), calcium nitrate (Ca(NO3)2), and magnesium sulfate (MgSO4), constituting over 75% of the total nutrient demand for hydroponics, cannot be recovered in appropriate form due to their high solubility, hindering their separated recovery from wastewater. To overcome this challenge, we outline a novel nutrient recovery approach that emphasizes the generation of multi-nutrient concentrates specifically designed to meet the requirements of hydroponic cultivation. Based on a theoretical assessment of nutrient and contaminant flows in a typical municipal WWTP, utilizing a steady-state model, we estimated that this novel approach could potentially supply up to 56% of the nutrient requirements of hydroponic systems. Finally, we outline fundamental design requirements for nutrient recovery systems based on this new approach. Achieving these nutrient recovery potentials could be technically feasible through a combination of activated sludge processes for nitrification, membrane-based desalination processes, and selective removal of interfering NaCl. However, given the limited investigation into such treatment trains, further research is essential to explore viable system designs for effective nutrient recovery for hydroponics.

Characteristics, fate, and effects of <i>Helicobacter pylori</i> in municipal wastewater treatment plant

<p><i>Helicobacter pylori</i> (<i>H. Pylori</i>) is a highly pathogenic bacterium that can be transmitted through various means, including wastewater, which serves as both a source and sink for <i>H. pylori.</i> In the wastewater treatment process, the exposure risk of <i>H. Pylori</i> escaping through bioaerosols is easily overlooked. In this study, the pollution characteristics and variation patterns of <i>H. Pylori</i> in wastewater, sludge, and air medium were systematically investigated in a typical municipal wastewater treatment plant (MWTP) applying anaerobic-anoxic-aerobic process through long-term sampling. The results indicated a significant reduction of <i>H. Pylori</i> in wastewater and accumulation in excess sludge following the wastewater treatment process. <i>H. Pylori</i> was also detected in bioaerosols due to its escape during wastewater treatment and sludge dewatering. The highest detection concentrations of <i>H. Pylori</i> in the air were found in the sludge dewatering house. O<sub>3</sub>, solar radiation, ambient temperature, and wind speed all had negative effects on the relative abundance and respirable proportion of airborne <i>H. pylori</i>. In addition, <i>H. Pylori</i> in bioaerosols had the potential to contaminate the ambient environment and posed a potential health risk to operational workers. This study will help to recognize the pollution of <i>H. Pylori</i> in MWTPs and raise the attention to occupational exposure among MWTP workers.</p>

Prioritization of micropollutants in municipal wastewater and the joint inhibitory effects of priority organic pollutants on Vibrio qinghaiensis sp.-Q67

Treatment of wastewater in municipal wastewater treatment plants has become a major barrier to organic pollutants entering the aquatic environment. In this study, qualitative screening of organic micropollutants was conducted in a typical municipal wastewater treatment plant (MWWTP) using gas chromatography-mass spectrometry (GC–MS). The identified compounds were prioritized according to their comprehensive scores ranked by detection frequency, semi-quantitative concentration, bioaccumulation, ecotoxicity, and biodegradability. The results showed dibutyl phthalate, antioxidant 2246, methyl stearate, 2,4,6-tri‑tert-butylphenol, and dioctyl phthalate had the top five scores and were ranked as priority organic pollutants in the municipal wastewater. The individual and joint toxicity determinations of the five compounds were carried out by a bioluminescence inhibition assay using Vibrio qinghaiensis sp.-Q67 (V. qinghaiensis). The individual toxicity assay results of these pollutants on V. qinghaiensis demonstrated that the order of the acute toxicity of the five priority organic pollutants was as follows: dioctyl phthalate> dibutyl phthalate> methyl stearate> antioxidant 2246> 2,4,6-tri‑tert-butylphenol. The joint toxicity showed partial addition or antagonism among these pollutants. The prediction results of the mixed toxicity were compared between the concentration addition model and the independent action model, indicating that a single traditional prediction model could not accurately predict the mixed toxicity of different types of organic pollutants, and that a comprehensive application of model prediction could improve the accuracy of mixed toxicity prediction. This method could provide a theoretical basis for systematic screening and toxicity prediction of pollutants in wastewater.

Bioassay-based identification and removal of target and suspect toxicants in municipal wastewater: Impacts of chemical properties and transformation

Municipal wastewater contains numerous chemicals and transformation products with highly diverse physiochemical properties and intrinsic toxicity; thus, it is imperative but challenging to identify major toxicants. Herein, toxicity identification evaluation (TIE) was applied to identify major toxicants in a typical municipal wastewater treatment plant (WWTP). Impacts of chemical properties on the removal of contaminants and toxicity at individual treatment stages were also examined. The WWTP influent caused 100% death of Daphnia magna and zebrafish embryos, and toxicity characterization suggested that organics, metals, and volatiles all contributed to the toxicity. Toxicity identification based on 189 target and approximately one-thousand suspect chemicals showed that toxicity contributions of organic contaminants, metals, and ammonia to D. magna were 77%, 4%, and 19%, respectively. Galaxolide, pyrene, phenanthrene, benzo[a]anthracene, fluoranthene, octinoxate, silver, and ammonia were identified as potential toxicants. Comparatively, the detected transformation products elicited lower toxicity than their respective parent contaminants. In contrast, the analyzed contaminants showed negligible contributions to the toxicity of zebrafish embryos. Removal efficiencies of these toxicants in WWTP were highly related to their hydrophobicity. Diverse transformation and removal efficiencies of contaminants in WWTPs may influence the chemical compositions in effluent and ultimately the risk to aquatic organisms in the receiving waterways.

Transformation products of tetracyclines in three typical municipal wastewater treatment plants

Antibiotics in the environment could undergo various processes with formation of transformation products, but little has been known about their occurrence and (eco)toxicological consequences. Here we investigated the occurrence and fate of nine transformation products of four tetracyclines (tetracycline, oxytetracycline, chlortetracycline and doxycycline) in three municipal wastewater treatment plants (WWTPs) in Guangzhou, China. The results showed the detection of all the tetracyclines and their transformation products in the WWTPs, with mean concentrations ranging from 17.8 ng/L (anhydrotetracycline) to 49.1 ng/L (oxytetracycline) in influent, 3.03 ng/L (tetracycline) to 6.94 ng/L (4-epi-chlortetracycline) in effluent, and 19.8 ng/g (isochlortetracycline) to 503 ng/g (4-epi-tertracycline) in sludge, respectively. The transformation products of tetracycline, oxytetracycline, chlortetracycline and doxycycline accounted for 73%–83%, 26%–52%, 70%–73% and 69%–74% of total concentrations, respectively. The aqueous removal rates of tetracyclines and their transformation products in the three WWTPs ranged from 18.4% (demethyl-chlortetracycline) to 93.7% (oxytetracycline). Mass balance analysis based on both aqueous and solid phase showed that their removals were mainly attributed to the sludge adsorption. Residual tetracyclines and their transformation products in the effluents would pose no obvious ecological risks to three aquatic organisms (green algae, daphnia and fish). However, 43.5% of sludge samples had high risks from these tetracyclines and transformation products, especially the compounds with poor biodegradability. The results from this study suggest that transformation products should be included in future environmental monitoring and control.

Bioaerosol in a typical municipal wastewater treatment plant: concentration, size distribution, and health risk assessment.

An investigation on bioaerosol in a wastewater treatment plant (WWTP) located in Xi'an, China, was conducted to understand the characteristics of bioaerosol released from wastewater and sludge treatment facilities because the bioaerosols may pose a threat to human health. Using the Andersen impactor sampler collection and colony-counting method, bioaerosol concentrations and size distributions were detected. The risk quotient method was used to evaluate the health risks associated with inhalation of bioaerosol for WWTP staff, based on the average daily dose rates of exposure. The health risk in relation to Legionella pneumophila was quantitatively calculated using quantitative microbial risk assessment (QMRA), based on the assumption of the percentage. The maximum concentration of airborne bacteria (3,767 ± 280 colony forming units (CFU)/m3) and fungi (8,775 ± 406 CFU/m3) occurred from the aerated grit chamber and sludge thickening house, respectively, which all exceeded 500 CFU/m3 as the acceptable guideline proposed by the American Conference of Governmental Industrial Hygienists. The particle size of airborne bacteria was mainly distributed in the first three stages (>3.3 µm), while that of airborne fungi was from the second to the fourth stage (2.1-7.0 µm). The hazard index exposure to bioaerosol for adult males and females by inhalation were higher than 1. The proportion of L. pneumophila should be strictly controlled below 10-8, based on the QMRA approach.

Behavior of Glyphosate in Wastewater Treatment Plants.

The herbicide glyphosate is frequently detected in surface waters and its occurrence is linked to agricultural as well as urban uses. Elevated concentrations downstream of wastewater treatment plants (WWTPs) suggest that municipal wastewater is an important source of glyphosate in surface waters. We therefore conducted a study at a typical municipal WWTP in Switzerland to characterize the seasonality of glyphosate occurrence, the removal efficiency, and the processes involved in glyphosate removal. Glyphosate was present in raw (mechanically treated) wastewater during the whole study period (April to November). A lab incubation experiment with activated sludge indicated negligible degradation of glyphosate. Lack of degradation combined with strong adsorption lead to substantial enrichment of the compound in the sludge. Due to this enrichment and the long residence time of activated sludge (several days, compared to hours for wastewater itself), concentrations in treated wastewater show comparatively little variation, whereas concentrations in raw wastewater may fluctuate considerably. Overall removal efficiencies were in the range of 71-96%. This behavior could be described qualitatively using a numerical model that included input of glyphosate via raw wastewater, adsorption to activated sludge, and export via treated wastewater and excess sludge, but excluded degradation processes.

The influence of alum based nutrient removal process on the physical, chemical and biological characteristics of phosphorus in the paper processing facility effluent

This study examined the physical, chemical and biological characteristics of the phosphorus (P) in the effluents from a paper processing facility before and after an alum based P removal process. The alum based treatment process reduced effluent total P concentrations from an average of 230 ± 103 (±1 SD) μg L−1 to an average of 36 ± 10 μg L−1. Ultra-filtration showed the treatment process shifted the P in these effluents from being 75 ± 9% particulate pre-removal to being 52 ± 0% dissolved and 27 ± 1% colloidal after the Trident P removal process. The alum removal process also reduced the fraction of reactive P in the dissolved and colloidal pools from 55% to 14%, respectively. Algal phosphorus bioavailability (BAP) bioassays showed the BAP of these effluents averaged 12 ± 9% of total P. Algal dissolved P uptake experiments indicated ≈ 30% of the dissolved P was converted to particulate P (which usually indicates algal uptake) during 21-day bioassays. However, treatments without algae indicated >80% of the apparent algal uptake may have been due to colloidal P forming flocs via physical-chemical processes. These analyses indicate the phosphorus contained in this paper processing facility's effluents had much lower bioavailability than the P in typical municipal wastewater treatment plant effluents.

Structure and function of the microbial consortia of activated sludge in typical municipal wastewater treatment plants in winter

To better understand the relationship between the environmental variables and microbial communities of activated sludge, we took winter samples from different biological treatment units (anaerobic, oxic, etc) from the WWTP’s of a number of Chinese cities. Differences in influent organic components and activated sludge microbial communities were identified by gas chromatography-mass spectrometry and high-throughput sequencing technology, respectively. Liquid nitrogen grinding pretreatment of samples was found to aid in the obtaining of a more bio-diversified sample. Influent type and dissolved oxygen concentration influenced the activated sludge microbial community structure. Nitrospira, Caldilineaceae and Anaerolineaceae were highly related to domestic wastewater treatment systems, whereas Thauera was the most abundant putative refractory aromatic hydrocarbon decomposer found in industrial wastewater treatment systems. Within the influent composition, we speculate that Thauera, Macellibacteroides and Desulfomicrobium are the key functional genera of the anaerobic environment of the textile dyeing industry wastewater treatment systems, whilst Thauera and Thiobacillus are key functional microbes in fine chemical wastewater treatment systems.

Mass loading and emission of thirty-seven pharmaceuticals in a typical municipal wastewater treatment plant in Hunan Province, Southern China

The occurrence, fate, mass loading and environmental emission of 37 pharmaceuticals were studied through an integrated approach involving both dissolved and adsorbed phase at a typical wastewater treatment plant in Hunan Province, Southern China. The results displayed the prevalence of 24 and 23 compounds in dissolved phase of influent and effluent, respectively. Fourteen compounds were found adsorbed onto sludge with a mean concentration ranging from 0.85 to 2900μg/kg dry weight. Twelve compounds exhibited high adsorption potential onto suspended particulate matter (SPM) with a mean fraction ranging from 8.8% (trimethoprim) to 97% (tetracycline). Furthermore, SPM showed a diverse absorbability in influent and effluent water circumstance. The overall elimination varied from −16% for lincomycin to 99% for paracetamol, while macrolides were able to withstand the whole treatment process. Mass balance analysis indicated that degradation was the predominant removal pathway for most compounds, and adsorption onto sludge combined with a minor portion of degradation explained for the reduction of tetracyclines and fluoroquinolones, whereas macrolides were recalcitrant to both two processes. The total mass loading was estimated to be up to 2800mg/d/1000 inhabitants and most compounds exhibited lower or comparable level comparing to the global published data. The total environmental emission was estimated up to be 1000mg/d/1000 inhabitants, and a value of 650mg/d/1000 inhabitants was obtained when considering merely the dissolved phase. This work would be helpful for the better understanding of ultimate fate and real pollution of pharmaceuticals in the water environment.

Emission factor for atmospheric ammonia from a typical municipal wastewater treatment plant in South China

Atmospheric ammonia (NH3), a common alkaline gas found in air, plays a significant role in atmospheric chemistry, such as in the formation of secondary particles. However, large uncertainties remain in the estimation of ammonia emissions from nonagricultural sources, such as wastewater treatment plants (WWTPs). In this study, the ammonia emission factors from a large WWTP utilizing three typical biological treatment techniques to process wastewater in South China were calculated using the US EPA's WATER9 model with three years of raw sewage measurements and information about the facility. The individual emission factors calculated were 0.15 ± 0.03, 0.24 ± 0.05, 0.29 ± 0.06, and 0.25 ± 0.05 g NH3 m−3 sewage for the adsorption-biodegradation activated sludge treatment process, the UNITANK process (an upgrade of the sequencing batch reactor activated sludge treatment process), and two slightly different anaerobic-anoxic-oxic treatment processes, respectively. The overall emission factor of the WWTP was 0.24 ± 0.06 g NH3m−3 sewage. The pH of the wastewater influent is likely an important factor affecting ammonia emissions, because higher emission factors existed at higher pH values. Based on the ammonia emission factor generated in this study, sewage treatment accounted for approximately 4% of the ammonia emissions for the urban area of South China's Pearl River Delta (PRD) in 2006, which is much less than the value of 34% estimated in previous studies. To reduce the large uncertainty in the estimation of ammonia emissions in China, more field measurements are required.

A study on the impact of sludge water on biological phosphorus removal process of the municipal wastewater treatment plant and its treatment process

At present, the research focus for sludge water was mainly concentrated on nitrogen removal, the study on the impact of sludge water with high concentration suspended solid (SS) and total phosphorus (TP) on phosphorus removal system is rare, and there is a gap in the research of processing technology for this type of sludge water The impact of sludge water on phosphorus removal process was investigated by field investigation and test analysis on an A2O process of a typical municipal wastewater treatment plant in Xi’an. Based on the sludge water quality characteristics of high concentration SS and TP, the study on coagulation dephosphorization technology was carried out. Through the sludge water coagulation mechanism analysis, the operating conditions of coagulation were optimized. The results of the study showed the appropriate polyaluminium chloride dosage was from 100 to 200 mg/L and the TP concentration after coagulation was about 14–11.6 mg/L. The coagulation process can effectively alleviate impact of sludge water on the system phosphorus removal process, and guarantee the outflow stable up-to-first grade A standards.

Antibiotic resistance, plasmid-mediated quinolone resistance (PMQR) genes and ampC gene in two typical municipal wastewater treatment plants

Antibiotic resistant bacteria and plasmid-mediated quinolone resistance genes and ampC gene were investigated for Escherichia coli isolates from two typical municipal wastewater treatment plants in both dry and wet seasons by using the antibiotic susceptibility test and PCR assay, respectively. The results showed that 98.4% of the isolates (1056) were found resistant to antibiotic(s) tested and 90.6% showed multiple resistances to at least three antibiotics. Tetracycline was found to have the highest resistance frequency (70.8%), followed by ampicillin (65.1%), whereas ceftazidime had the lowest resistance frequency of 9.0%. Moreover, 39.2% of the E. coli isolates were carrying plasmids. intI1 had the highest detection rate in the plasmids (38.1%), followed by qnrS, ampC, qnrB, intI2 and aac(6')-Ib-cr. The disinfection process (UV and chlorination) could significantly reduce the number of bacteria, but percentage of the resistant bacteria, resistance frequency for each antibiotic, MAR index and detection rate of the plasmid-mediated resistance genes were all found increasing in the effluents of biological units. The results of this study showed that a more frequent horizontal gene transfer occurred in the biological units. Wastewater treatment plants were an important medium for the recombination and dissemination of antibiotic resistance genes in the environment.

Contents and Characteristics of Phthalic Acid Esters in Municipal Sewage Sludge in Jiangsu Province

Concentrations of 6 kinds of phthalic acid esters (PAEs) in sewage sludge from 20 typical municipal wastewater treatment plants (WWTPs) in Jiangsu province were determined by gas chromatography-mass spectrometry (GC-MS) . The results shows that the sewage sludge samples contain phthalic acid ester compounds, which total content of phthalic acid esters ( PAEs) range from 15.126 to 71.107 ug/g (dry sludge). The content of diethylhexyl phthalate (DEHP) is the highest, which amounts more than 80% of total phthalic acid esters (PAE); the content of dimethyl phthalate (DMP) is low ,which is less than 1.0 ug/g;Diethyl phthalate (DEP), dibutyl phthalate (DBP) and benzyl butyl phthalate (BBP) are detected in each sludge sample, but which content display greater difference; Dioctyl phthalate (DOP) in most cities is not detected.

Partial oxidative gasification of municipal sludge in subcritical and supercritical water

Subcritical and supercritical water gasification of dewatered sewage sludge obtained from a typical municipal wastewater treatment plant was investigated in a one-litre high-pressure autoclave at temperatures of 300–400 °C and pressures of 17.5–23.5 MPa. The sludge (without catalyst) was gasified at subcritical and supercritical water conditions, with different reaction times ranging from 30 to 60 min. The results showed that gaseous product yield increased with increasing temperature and reaction time. Gas products consisted primarily of hydrogen, carbon dioxide, methane, carbon monoxide and other light hydrocarbons. The liquid products contained high levels of organic matter, ammonia nitrogen and a few heavy metals. Compared with the landfilling of sewage sludge, the solid residues were in accordance with the Chinese standard for sludge quality in co-landfilling even without further treatment. In addition, the heavy metals in solid products exhibited more stable characteristics attributable to the reduced leaching toxicity after supercritical water gasification.

Microconstituents – What is a Typical Municipal Wastewater Treatment Plant Designer to Do?

Microconstituents – What is a Typical Municipal Wastewater Treatment Plant Designer to Do?