Operation Of Wastewater Treatment Plants Research Articles

Removal of Estrogens in Kuwaiti Municipal Wastewater Treatment Plants

Presence of estrogens in the environment is gaining great attention worldwide due to their potential adverse effects on aquatic ecosystems and public health. Estrogens pollution is generally related to incomplete removal at wastewater treatment plants (WWTPs). To ascertain the status of estrogens pollution in Kuwait, this study evaluated the removals of estrogens at municipal WWTPs in Kuwait. The solid-phase extraction gas chromatography-mass spectrometry method was used for the determination of estrogens concentrations in influent and effluent streams of three main municipal WWTPs (Kabd, Suliabiya and Umm-Al-Haiman). Obtained results indicated that concentration of estrogens in the influent streams ranged from 0.0 to 474 ng/l, while that in the effluent streams were between 0.0 to 233 ng/l. Both influent and effluent concentrations showed high variations around mean values. Average removal rates of total estrogens were found to be 13%, 79%, 68%, for Kabd, Suliabiya and Umm-Al-Haiman, respectively. This study indicated that operation of municipal WWTPs in Kuwait needs to be upgraded/optimized in order to maximize estrogens’ elimination. It also revealed that Kuwait needs to regulate discharges of estrogens from WWTPs in order to prevent further pollution of marine environment and groundwater.

Online Monitoring of Effluent Quality for Assessing the Effect of Wastewater Treatment Plant to Discharge into the Receiving Water: a review

In general, industries that use water in their production process will produce wastewater which usually contains a lot of polluting contaminants. It will affects the surrounding environment by contaminating the water bodies, which will adversely affect the health life of all living beings. Pollution that occurs in the some rivers in Indonesia has begun to raise concern for Indonesian Goverment. Some of the river locations already have heavy poluted status. The pollution is mostly caused by industrial waste and domestic waste along the river. Treatment plants for wastewater effluents are mandatory for any industry which discharges their wastewater effluents into the environment. Information on monitoring the quality of industrial wastewater is very important to be perceived by examining changes in water quality condition that are getting better or worse. It is necessary to develop a system that monitors the condition of industrial wastewater. Industrial wastewater monitoring is a device system that collects real time data. Online monitoring technology is one part that plays an important role in supporting activities to control marine environmental pollution. Real‐time monitoring of wastewater quality remains an unresolved problem to the wastewater treatment industry. One of the problem in most industries in Indonesia is that the operational and performance of wastewater treatment plants (WWTP) are still not optimal, and need to be improved. The application of industrial technology concept 4.0 and automation systems in the industry is expected to improve the WWTP supervision process which has advantages such as reducing down time, reducing consumption of raw materials, reducing the energy used, increasing productivity, improving product quality and making efficient use of resources and processes, so as to reduce industrial operating costs.

A review of 17α-ethynylestradiol (EE2) in surface water across 32 countries: Sources, concentrations, and potential estrogenic effects

17α-ethynylestradiol (EE2) is a synthetic estrogen with very strong estrogenic potency. Due to its wide usage in human and livestock as well as its high recalcitration to biodegradation, it was ubiquitous in different environment. This review summarized EE2 concentration levels in surface waters among 32 countries across seven continents. EE2 concentrations varied greatly in different surface waters, which ranged from not detected to 17,112 ng/L. The top 10 countries ranked in the order of high to low average EE2 concentration in surface water, were Vietnam, Cambodia, China, Laos, Brazil, Argentina, Kuwait, Thailand, Indonesia and Portugal, with the respective mean concentrations of 27.7, 22.1, 21.5, 21.1, 13.6, 9.6, 9.5, 8.8, 7.6 and 6.6 ng/L. Generally speaking, the EE2 concentration levels in surface waters in developing countries were much higher than those in developed countries. EE2 in effluent of municipal wastewater treatment plant (WWTP) was the dominant source to most countries, which suggested that improving the EE2 removal performance of municipal WWTP is the key to mitigate EE2 contamination to surface water body. Livestock, hospital, pharmacy factory and aquaculture wastewaters were also the important sources, but further work should be performed to elucidate their contribution. Evaluation based on estrogenic effects, the EE2-derived estrogen equivalence in surface waters ranged from 0 to 33 ng E2/L, among which about 65% of surface waters among 32 countries were at risk or high risk, indicating global serious EE2 contamination. Main findingEE2 concentration in surface waters across 32 countries were summarized, along which its potential estrogenic effects were evaluated.

Identifying and Estimating the Location of Sources of Industrial Pollution in the Sewage Network.

Harsh pollutants that are illegally disposed in the sewer network may spread beyond the sewer network—e.g., through leakages leading to groundwater reservoirs—and may also impair the correct operation of wastewater treatment plants. Consequently, such pollutants pose serious threats to water bodies, to the natural environment and, therefore, to all life. In this article, we focus on the problem of identifying a wastewater pollutant and localizing its source point in the wastewater network, given a time-series of wastewater measurements collected by sensors positioned across the sewer network. We provide a solution to the problem by solving two linked sub-problems. The first sub-problem concerns the detection and identification of the flowing pollutants in wastewater, i.e., assessing whether a given time-series corresponds to a contamination event and determining what the polluting substance caused it. This problem is solved using random forest classifiers. The second sub-problem relates to the estimation of the distance between the point of measurement and the pollutant source, when considering the outcome of substance identification sub-problem. The XGBoost algorithm is used to predict the distance from the source to the sensor. Both of the models are trained using simulated electrical conductivity and pH measurements of wastewater in sewers of a european city sub-catchment area. Our experiments show that: (a) resulting precision and recall values of the solution to the identification sub-problem can be both as high as 96%, and that (b) the median of the error that is obtained for the estimation of the source location sub-problem can be as low as 6.30 m.

Effluent temporal collective behaviors of a wastewater treatment plant community

The effluent temporal characteristics of a plant community, which is composed of wastewater treatment plants (WWTPs) treating similar influent under similar conditions, contribute to understanding the performance of WWTPs. However, studies on this topic have rarely been reported. In this study, effluent data from 92 municipal plants in the same province of China collected during 2014–2019 were analyzed as time series to elucidate collective behaviors and to identify specific plants with abnormal effluent. The most significant periodic cycles for ammonia and chemical oxygen demand (COD) were 183 days and 91 days, respectively, suggesting that the temporal variation of effluent ammonia was mainly dependent on weather conditions such as temperature and the effluent COD was primarily dependent on loading rates. Interestingly, both ammonia and COD exhibited quasi-biweekly variation with a period of approximately 13 days, which is a weather-dependent collective feature, showing a synchronous variation of a plant community. Therefore, a difference in the quasi-biweekly variation pattern of a specific plant from a plant community is proposed to identify the outliers and further help to tune these plants. This study's findings suggest that the temporal collective behaviors of a plant community should also be considered for the evaluation of WWTPs, especially when online data are readily available.

Insights into Nitrous Oxide Mitigation Strategies in Wastewater Treatment and Challenges for Wider Implementation.

Nitrous oxide (N2O) emissions account for the majority of the carbon footprint of wastewater treatment plants (WWTPs). Many N2O mitigation strategies have since been developed while a holistic view is still missing. This article reviews the state-of-the-art of N2O mitigation studies in wastewater treatment. Through analyzing existing studies, this article presents the essential knowledge to guide N2O mitigations, and the logics behind mitigation strategies. In practice, mitigations are mainly carried out by aeration control, feed scheme optimization, and process optimization. Despite increasingly more studies, real implementation remains rare, which is a combined result of unclear climate change policies/incentives, as well as technical challenges. Five critical technical challenges, as well as opportunities, of N2O mitigations were identified. It is proposed that (i) quantification methods for overall N2O emissions and pathway contributions need improvement; (ii) a reliable while straightforward mathematical model is required to quantify benefits and compare mitigation strategies; (iii) tailored risk assessment needs to be conducted for WWTPs, in which more long-term full-scale trials of N2O mitigation are urgently needed to enable robust assessments of the resulting operational costs and impact on nutrient removal performance; (iv) current mitigation strategies focus on centralized WWTPs, more investigations are warranted for decentralised systems, especially decentralized activated sludge WWTPs; and (v) N2O may be mitigated by adopting novel strategies promoting N2O reduction denitrification or microorganisms that emit less N2O. Overall, we conclude N2O mitigation research is reaching a maturity while challenges still exist for a wider implementation, especially in relation to the reliability of N2O mitigation strategies and potential risks to nutrient removal performances of WWTPs.

Economic Analyses of the Seadrift Wind-Aided Wastewater Treatment Plant Operations

Seadrift is located on the Texas Gulf Coast with a population of 1,364 people as of the 2010 U.S. Census. In 2012, the city started operation of a $610,878 wind turbine, dedicated to its wastewater treatment plant. The city hoped to save $25,500 yearly using wind energy to displace some of the plant’s electrical demand. The plant’s average load is 0.05 million gallons per day, requiring 236,000 kWh (8.05*108 BTU) yearly. The paper details how Seadrift used manufacturer curves to predict turbine energy production, and how preliminary geotechnical, economic, and environmental analyses help design renewable energy projects. From 2012 to 2015, Seadrift saved $15,928 per year, with yearly wind energy production of 155,738 kWh (5.31*108 BTU) and net present value of $211,493. This study shows how government agencies and rural communities can collaborate to find economically viable solutions to water-energy nexus challenges in Texas and beyond. Citation: Mbarga AHA, Rainwater K, Song L, Theodore C, Williams WR. 2021. Economic Analyses of the Seadrift Wind-Aided Wastewater Treatment Plant Operations. Texas Water Journal. 12(1):42-57. Available from: https://doi.org/10.21423/twj.v12i1.7096.

Decentralized management of sewage using septic tanks and anaerobic filters and its potential to comply with required standards in a developing country: a case study in Brazil.

To investigate the feasibility of implementing decentralized sewage treatment systems aiming to meet environmental standards, the performance of three decentralized wastewater treatment plants (WWTPs) comprising septic tanks and anaerobic filters (ST+AF) was evaluated. The ability of the WWTPs to comply with the provisions of the legislation and the technical literature was investigated by monitoring physical and chemical parameters at the entrance and exit of the WWTPs, from May 2017 to August 2018. Considering that factors such as operational routine, design of treatment systems, and the existence of pluvial contributions to the sewage network can influence the performance of WWTPs, an investigation of these factors was conducted. The results show that the ST+AF systems can meet the requirements of the legislation. The hypothesis raised in this study is that factors such as cleaning routine and dimensioning of the treatment units can influence the performance of the systems. The best performance was found in the WWTP submitted to frequent cleaning and whose ST dimensions were closest to those recommended by technical standards. The average annual efficiencies of removal of biochemical oxygen demand (BOD) and chemical oxygen demand (COD) in this WWTP assumed values of 93 and 89%, while its solid effluents presented concentrations 82% below the limit established in legislation. Finally, no rainwater contributions were found in the WWTPs, which may be associated with the use of short collection networks in decentralized systems.

Risk Assessment and Sustainability of Wastewater Treatment Plant Operation

Water and water management, which also includes wastewater treatment plants (WWTPs), are considered essential elements critical infrastructure. A disruption of their operation can result in the discharge of wastewater into the environment without having been adequately treated. This can cause health problems, contamination of soil, groundwater and surface water, etc. In order to provide operational safety and sustainability of WWTP operation, it is necessary to establish protection against potential risk activation, together with risk minimization and enhanced preparedness to address the risks. The article deals with the application of risk management stages on the selected object of the municipal WWTP facility in the form of a case study. The risk identification phase consisted of the identification of assets and risks. The assets were grouped together due to the complexity of the WWTP operation. A combination of methods, a safety audit, a checklist and semi-structured interviews were used to identify the risks in three iterations. A risk register was created as a result of the risk identification phase. Subsequently, a risk analysis was carried out, in which the scenarios of the risk impact on the assets were examined, the index levels of probability and impacts were determined, and the risk estimate was performed. The Bowtie Analysis Method was used to illustrate the causes and consequences for one of the critical risks. The result of the study is the risk evaluation identified undesirable and unacceptable risks for which risk management methods were proposed

A Random Forest Model for the Prediction of FOG Content in Inlet Wastewater from Urban WWTPs

The content of fats, oils, and greases (FOG) in wastewater, as a result of food preparation, both in homes and in different commercial and industrial activities, is a growing problem. In addition to the blockages generated in the sanitary networks, it also represents a difficulty for the performance of wastewater treatment plants (WWTP), increasing energy and maintenance costs and worsening the performance of downstream treatment processes. The pretreatment stage of these facilities is responsible for removing most of the FOG to avoid these problems. However, so far, optimization has been limited to the correct design and initial installation dimensioning. Proper management of this initial stage is left to the experience of the operators to adjust the process when changes occur in the characteristics of the wastewater inlet. The main difficulty is the large number of factors influencing these changes. In this work, a prediction model of the FOG content in the inlet water is presented. The model is capable of correctly predicting 98.45% of the cases in training and 72.73% in testing, with a relative error of 10%. It was developed using random forest (RF) and the good results obtained (R2 = 0.9348 and RMSE = 0.089 in test) will make it possible to improve operations in this initial stage. The good features of this machine learning algorithm had not been used, so far, in the modeling of pretreatment parameters. This novel approach will result in a global improvement in the performance of this type of facility allowing early adoption of adjustments to the pretreatment process to remove the maximum amount of FOG.

Multi-objective optimization based controller design for improved wastewater treatment plant operation

Wastewater treatment plants (WWTPs) are highly complex and nonlinear processes. The challenge lies in the design of a control strategy to lower the operational costs and to enhance the effluent quality simultaneously. In this research, PI controllers are designed for control of biological WWTPs and Benchmark Simulation Model No. 1 (BSM1) is used as a working platform. Genetic Algorithms which are a subclass of evolutionary search algorithms are used to determine optimal PI controller parameters to achieve improved effluent quality with minimum operational expenses. Different objective functions such as Indices for Effluent Quality and Operational Cost, and Integral Square Error (ISE) for the design of controllers are considered. A Pareto optimal curve is plotted for different conditions and the best combination is evaluated. The results indicated that the controllers designed using this approach provided improved WWTP operation.

The effects of engineered nanoparticles on nitrification during biological wastewater treatment.

Technological advancements in the past few decades have made it possible to manufacture nanomaterials at a large scale, and engineered nanoparticles (ENPs) are increasingly found in consumer products, such as cosmetics, sports products, and LED displays. A large amount of these ENPs end up in wastewater and potentially impact the performance of wastewater treatment plants (WWTPs). One important function of the WWTP is nitrification, which is carried out by the actions of two groups of bacteria, ammonia-oxidizing bacteria (AOB), and nitrite-oxidizing bacteria (NOB). Since most ENPs are found to have or are designed to have antimicrobial activities, it is a legitimate concern that ENPs entering WWTPs may have negative impacts on nitrification. In this paper, the effects of ENPs on nitrification are discussed, focusing mainly on autotrophic nitrification by AOBs and NOBs. This review also covers ENPeffects on anaerobic ammonium oxidation (anammox). Generally, nitrifiers in pure and mixed cultures can be inhibited by a variety of ENPs, but stress response mechanisms may attenuate toxicity. Long-term studies demonstrated that a wide range of NPs could cause severe deterioration of AOBs and/or NOBs when the influent concentration exceeded an inhibition threshold. Proposed mechanisms include the generation of reactive oxygen species, dissolved metals, physical disruption of cell membranes, bacterial engulfment, and intracellular accumulation of ENPs. Future research needs are also discussed.

Impact of source-separation of urine on effluent quality, energy consumption and greenhouse gas emissions of a decentralized wastewater treatment plant

The impact of urine diversion on the biological treatment processes at a decentralized wastewater treatment plant (WWTP) was investigated. BioWin software was used for the simulations, and the model was firstly validated with data from a real WWTP. The simulations showed that upto 82 % N, 30 % P, 6% chemical oxygen demand (COD) load to the WWTP can be reduced by complete urine diversion but effluent N reduction was notable up to 75 % urine diversion. Under the current WWTP operating conditions, the simulations suggest that 33 % of aeration energy can be saved by 90 % urine diversion. Direct N2O and CO2 emissions in the treatment processes can also be reduced by 98 % and 25 % respectively. Indirect green house gas emissions can also be reduced by 20 %. Overall, the reduction in the discharge of nutrients and in the operation of blowers was found to contribute to a 22 % reduction in the operating costs (on energy consumption and nutrient discharge).

Optimal control towards sustainable wastewater treatment plants based on multi-agent reinforcement learning

Wastewater treatment plants (WWTPs) are designed to eliminate pollutants and alleviate environmental pollution resulting from human activities. However, the construction and operation of WWTPs consume resources, emit greenhouse gases (GHGs) and produce residual sludge, thus require further optimization. WWTPs are complex to control and optimize because of high non-linearity and variation. This study used a novel technique, multi-agent deep reinforcement learning (MADRL), to simultaneously optimize dissolved oxygen (DO) and chemical dosage in a WWTP. The reward function was specially designed from life cycle perspective to achieve sustainable optimization. Five scenarios were considered: baseline, three different effluent quality and cost-oriented scenarios. The result shows that optimization based on LCA has lower environmental impacts compared to baseline scenario, as cost, energy consumption and greenhouse gas emissions reduce to 0.890 CNY/m3-ww, 0.530 kWh/m3-ww, 2.491 kg CO2-eq/m3-ww respectively. The cost-oriented control strategy exhibits comparable overall performance to the LCA-driven strategy since it sacrifices environmental benefits but has lower cost as 0.873 CNY/m3-ww. It is worth mentioning that the retrofitting of WWTPs based on resources should be implemented with the consideration of impact transfer. Specifically, LCA-SW scenario decreases 10 kg PO4-eq in eutrophication potential compared to the baseline within 10 days, while significantly increases other indicators. The major contributors of each indicator are identified for future study and improvement. Last, the authors discussed that novel dynamic control strategies required advanced sensors or a large amount of data, so the selection of control strategies should also consider economic and ecological conditions. In a nutshell, there are still limitations of this work and future studies are required.

Reconstruction of treatment facilities for wastewater treatment at "Antonov" State Enterprise

The main priorities of Ukraine's foreign policy in the field of environmental protection have always been political and institutional rapprochement with the European Union (EU). In this regard, Ukraine has made commitments to gradually harmonize national legislation with EU legislation. Therefore, the "Directive 2000/60/EC of the European Parliament and of the Council establishing a framework for the Community action in the field of water policy" which aimed at improving the protection and improvement of the aquatic environment through specific measures to reduce discharges, emissions and losses of priority substances, as well as the cessation or elimination of discharges, emissions and losses of hazardous substances, currently requires active implementation. Therefore, the issue of reconstruction of wastewater treatment plants at the enterprise of SE "Antonov" is very relevant. An analysis of the operation of wastewater treatment plants at the enterprise of SE "Antonov" was performed. Today, the entire complex of treatment facilities needs reconstruction with design work to implement the latest technologies for extraction of petroleum products from water and surface wastewater treatment, as well as the organization of self-flowing water treatment regime. Measures for the reconstruction of treatment facilities are proposed. The technology of operation of treatment facilities on the principle of self-flowing water treatment regime is offered, which will allow saving energy resources. An improved technology for extraction of petroleum products, floating and suspended solids from wastewater, and purification of effluents for dissolved petroleum products removal is proposed. Proposed measures will improve the environmental situation in reservoirs where treated water flows.

Evaluation of Regional Domestic Waste Water Treatment Plant Performance in Cimahi City

Domestic wastewater treatment plant performance (WWTP) currently refers to stringent wastewater quality standards (Minister of Environment and Forestry Regulation No. 68 of 2016) considering potential environmental degradation because of pollutants in the wastewater. This study evaluated the performance of the Regional Domestic WWTP in Cimahi City. Cimahi has 10 WWTPs which were operated by an Anaerobic Baffled Reactor system. Periodic monitoring only measured the wastewater characteristics after treatment with parameters: total suspended solids (TSS), ammonia, chemical oxygen demand(COD), biological oxygen demand(BOD), and oil and grease. Therefore, wastewater characteristics were measured before and after treatment at selected WWTP during peak and non-peak hours, with TSS, ammonia, and COD. Important hydraulic factors were also measured: flow velocity at peak and non-peak hours, hydraulic detention time, and sludge height. Effluent from all WWTPs did not meet the standard. However, WWTPs with detention time >2 days produced parameter concentrations closed to the maximum value. The selected WWTP has a 5.7days detention time with removal efficiency for COD 57.52%, and TSS 42.56%, during peak period and COD 60.19% and TSS 34.84% for a non-peak period, but ammonia concentration did not decrease. Overall, WWTP has not been able to meet quality standards and the quality.

A review of the adsorption-biological hybrid processes for the abatement of emerging pollutants: Removal efficiencies, physicochemical analysis, and economic evaluation

The limited efficiency of conventional wastewater treatment plants (WWTPs) in emerging pollutants (EPs) removal encourages the development of alternative technologies for the adequate treatment of wastewater, due to its adverse effects on human health and ecosystems. The biological, physical or chemical hybrid technologies to treat EPs results interesting since they can enhance the performance of WWTPs. Among them, hybrid adsorption/biological technology could offer different possibilities that are explored in this work (PAC-MBR, PACT/GAC-CAS, BAC configurations). In this way, different variations in the adsorption process have been considered: the form of the adsorbent, the feed to the system, and the type of biological process, either conventional activated sludge (CAS), membrane bioreactor (MBR) or biofilm systems. For each combination, the removal efficiency of micropollutants, classified according to their use into pharmaceuticals, personal care products (PCPs) and other micropollutants (mainly benzotriazoles) was analysed. From reported data, it was observed a beneficial synergistic effect of dipole moment and octanol-water partition coefficient on the removal efficiency of micropollutants by adsorption/biological hybrid technology. Finally, a preliminary economic evaluation of the powdered activated carbon in a conventional activated sludge reactor (PACT), powdered activated carbon-membrane bioreactor (PAC-MBR) and biological activated carbon (BAC) hybrid systems was carried out by analysing the capital expenditure (CAPEX) of plants for capacities up to 75,000 m3d-1. Likewise, estimations of adsorbent concentration for a hypothetical plant with a capacity of 10,000 m3d-1 is presented. Among these hybrid configurations, PAC-MBR achieved the highest micropollutant elimination percentages; however, it presents the highest CAPEX and activated carbon requirements.

Dairy wastewater processing and automatic control for waste recovery at the municipal wastewater treatment plant based on modelling investigations

Based on the calibrated model for an Anaerobic-Anoxic-Oxic (A2O) municipal wastewater treatment plant (WWTP), this research investigated and proposed feasible solutions, control system configurations and optimal operating conditions for the dairy wastewater processing. The steady state study on adding different daily amounts of dairy wastewater in the WWTP water line revealed the most efficient amount to be treated by finding a minimum of the total nitrogen concentration in the water effluent. The dynamic investigations on adding different daily amounts of diary wastewater demonstrated the incentives of the proposed cascade control system configurations, based on the ammonia or nitrates concentration control in the aerated reactors, associated to nitrates and nitrites concentration control in the anoxic reactor. The best periods of time and duration for scheduling the dairy wastewater processing were searched and found. Preliminary results showed the incentives of the additional dairy wastewater distribution during 2 h, at the highest influent concentration moments. Further investigations, relying on the genetic algorithm optimization method revealed that better daily scheduling of the dairy wastewater addition may be obtained. Compared to normal operation, the optimal scheduling program of the dairy wastewater treatment showed an overall performance index improvement of 13.36%, when the daily 1:52 p.m. moment of time and the duration of about 1 h program, found by optimization, were applied. Results demonstrate the dual incentives of the carbon and nutrients recovery, associated to the energy and effluent quality benefits on WWTP operation.

Removal of Suspended Solids Using Pumice Stone in Integrated Fixed Film Activated Sludge Process

Wastewater treatment plants operators prefer to make adjustments because they are more cost effective, to use the existing tank instead of building new ones. In this case an imported materials would be used as bio-loads to increase biomass and thus maintain efficiency as the next organic loading increases.In the present study, a local substance "pumice stone" was used as a biological carrier in the aeration tank, and the experiments were carried out in five stages: without biological carriers, filling ratio of 4%,10%,20%, and25% with pumice stone, the maximum organic loading at each stage (1.1884, 1.2144, 1.9432, 2.7768, 3.3141)g BOD /l.d respectively.Other experiments were carried out to determine the best filling ratio, the SS removal ratio was (67.57%, 69.5%,79.44%,89.61%,and 99.2%) when the filling ratio with pumice stone was (0, 4, 10, 20, and 25)% respectively, at organic loading 2 ± 0.0528 g BOD /l.d, so the best filling ratio of pumice stone was 25% . In this case an imported materials would be used as bio-loads to increase biomass and thus maintain efficiency as the next organic loading increases. In this research, a local substance "pumice stone" was used as a biological carrier in the aeration tank, and the experiments were carried out in five stages: without biological carriers, filling ratio of 4%,10%,20%, and25% with pumice stone, The maximum organic loading at each stage (1.1884, 1.2144, 1.9432, 2.7768, 3.3141)g BOD /l.d respectively. The SS removal ratio was when we operatio without biological carriers and with pumice stone with a filling ratio of 4% (82.86 % and 84.96 %) respectively, at organic loading 1.15 ± 0.0384 g BOD / d, the SS removal ratio when using pumice stone with a filling ratio of 4% and 10% was (80.36%, 91.59%) respectively, at organic loading 1.25 ± 0.024 g BOD /l.d The SS removal ratio when using pumice stone with a filling ratio of 10% and 20% was (79.44%, 91.23%) respectively, at organic loading 2 ± 0.0528 g BOD /l.d , and The SS removal ratio when using pumice stone with a filling ratio of 20% and 25% was (80.45 %, 92.28%) respectively, at organic loading 2.85 ± 0.0624 g BOD /l.d ,which means there is improvement in yield using pumice stone with filling ratio 4%,10%,20 and 25% by 2.1% ,11.23%,11.79% and 11.83%, respectively.

The presence of SARS-CoV-2 in raw and treated wastewater in 3 cities of Iran: Tehran, Qom and Anzali during coronavirus disease 2019 (COVID-19) outbreak.

This study aimed to identifying the presence of SARS-CoV-2 RNA in raw and treated wastewater during the COVID-19 outbreak in Tehran, Qom and Anzali cities (Iran). From three wastewater treatment plants (WWTPs), 28 treated and untreated wastewater composite samples were collected from April 4 to May 2, 2020. In this study, polyethylene glycol 6000 (PEG 6000) was used through one-step real-time quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) for identification of RNA viruses. SARS-CoV-2 RNA was elicited from wastewater composite samples in all inlet samples taken from the three above mentioned cities. The results of outlet samples were as follows: 1) Results from Qom and East Anzali outlets showed no trace of SARS-CoV-2 RNA despite the difference in treatment disinfection method used (chlorine vs. ultraviolet (UV) disinfection). 2. In Tehran, SARS-CoV-2 RNA was not detected in any of the outlet samples taken from the modules disinfected by UV. Out of the four samples taken from the modules disinfected by chlorine, two were positive for the SARS-CoV-2 RNA which could have been caused by deficiencies in operation and maintenance. It can be concluded that meeting the standards of operation and maintenance (O&M) in WWTPs can considerably ensure that wastewater does not act as one of the roots of transmission for the disease.