Seasonal Variations in the Performance of the Amberpet Wastewater Treatment Plant: Assessing the Impact of Temperature and Dissolved Oxygen.

Abstract

Water resources sources have deteriorated in recent years due to rapid population growth, chemical industry effluents, agricultural practices, and climate change. The primary cause of contamination of water-bodies is due to disposal of untreated sewage water pollution. Hence effective sewage treatment is necessary to safeguard water-bodies from contamination. Many cutting-edge techniques have been developed in recent years to increase the effectiveness of the removal of organic matter and nutrients by Waste Water Treatment Plants (WWTPs). To comprehend the effectiveness of wastewater treatment, the current study considered a Sewage Treatment Plant (STP) located in Amberpet, Hyderabad. The capacity of the STP at Amberpet is 339 MLD (Million Liters per Day) and is evaluated by collecting 156 samples for 12 months (January 2018 – December 2018). The data collected was based on grab and composite collection. In STPs, grab sampling and composite sampling are two frequently used techniques for gathering wastewater samples. Grab sampling is the process of taking one wastewater sample at a specific time. Contrarily, composite sampling involves collecting multiple effluent samples over a predetermined period. An STP aims to minimize or remove organic debris, sediments, disease-causing organisms, and other pollutants in sewage water before disposing into streams and other water bodies. The current study observed the removal efficiencies of the constituents such as Total Suspended Solids (TSS), Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), and several other parameters. This investigation assesses whether the effluents emitted into the river body are within the National River Conservative Directorate (NRCD) set limitations as the treated sewage water is discharged into the Musi River (a tributary of Krishna Basin). This study investigated the seasonal variation of WWTP efficiencies for different water quality parameters for the year 2018. The study was conducted over four seasons: winter (December, January, February), pre-monsoon (March, April, May), monsoon (June, July, August, September), and post-monsoon (October, November). The study analyzed the influents and effluents of each available water quality parameter, using both grab and composite sampling and the performance efficiency of STP. For each water quality parameter, the findings revealed considerable seasonal fluctuations in treatment plant efficiencies. For example, if Dissolved Oxygen (DO) level is too low, the microorganisms may become stressed or die, leading to reduced treatment efficiency. On the other hand, if DO level is too high, it can lead to the growth of aerobic bacteria that consume DO, reducing the available oxygen for the treatment process. Therefore, it is important to monitor the DO levels in the STP regularly and maintain them within the recommended range to ensure efficient and effective treatment of the wastewater. The type of treatment technique used in STP determines the DO saturation level necessary for a sewage treatment facility. For an activated sludge process, the DO saturation level should typically be kept between 2 and 3 mg/L, and between 1 and 2 mg/L for a trickling filter process. Water temperature is a prominent variable for water quality and aquatic habitat affecting saturation dissolved oxygen concentrations, algal metabolism, fish growth, and production in aquatic systems. Water temperature also signifies the health of the river water body and regulates many physical and chemical parameters related to river water quality parameters, which speculatively depend on many factors. The study provided valuable insights into the influence of water temperature on saturation oxygen levels in the water, highlighting the importance of considering temperature as a crucial environmental factor in assessing water quality. So far, most River Water Temperature (RWT) models are either physical or datadriven models requiring large amounts of hydrological and meteorological observations. Many climate change studies have been conducted with increasing stream water temperatures, but how it affects saturated DO levels have not been addressed. To address these, the present work aims to work with a hybrid model - Air2Stream as a function of air temperature and discharge and also demonstrates how the Air2Stream method can be used to generate accurate RWT predictions and subsequent DO concentrations in river water quality modeling. RWT, which combines the ideas of the heat budget equation that generalizes physical processes and infers relationships between input and output data, can be predicted using the Air2Stream model. With two river gauging stations at Mantralayam, Shimoga in the Krishna River Basin, the efficiency of the suggested modeling framework is demonstrated. By comparing simulated RWT time series with matched observations and calculating the Nash Sutcliffe Efficiency (NSE), model performance was assessed. According to model results, NSE values for the calibration period for the study sites ranged from 0.76 to 0.97. Saturated DO levels are evaluated using the simulated RWT. The estimated saturated DO concentrations were ranging from 7.3% to 10.08% at the Mantralayam station, and from 6.78% to 9.27% at the Shimoga station. According to the study, wastewater treatment operations are affected by DO levels since DO saturation levels in wastewater were found to be much lower than those in river water. Additionally, the study discovered that downstream of wastewater discharge stations, DO saturation levels in river water were much lower than upstream, indicating that wastewater release may be a key factor in the decreased DO levels in rivers. The study's findings show how important effective wastewater treatment methods are for maintaining the water quality in river systems downstream. WWTPs must optimize their treatment processes in order to maintain appropriate DO levels and minimize their influence on downstream water quality. The study concluded that the efficiency of the treatment plant varied significantly for each water quality parameter, with some parameters showing better efficiencies during some seasons than others. The results of this study emphasize the significance of considering seasonal fluctuations into account when designing and operating WWTPs. To ensure the efficient removal of pollutants and the preservation of downstream water quality, WWTPs must optimize their treatment procedures to maintain consistent and dependable treatment efficiency throughout the year. The efficient removal of these contaminants is crucial to ensure the safe reuse of treated wastewater for agricultural purposes. Therefore, continuous monitoring and analysis of the quality of treated wastewater is necessary to ensure that it meets the required standards for agricultural irrigation. Additionally, effective management practices such as crop selection, irrigation methods, and soil amendments can help mitigate the potential risks associated with the use of treated wastewater for irrigation.