EVALUATION OF ADVANCED ON-SITE SEWAGE TREATMENT SYSTEM (JOHKASOU) UNDER STRESS CONDITIONS

Abstract

The Johkasou system is a decentralized wastewater treatment technology implemented at the Indian Institute of Technology Roorkee (IIT-R) to treat domestic wastewater. This study assessed the Johkasou system's performance at the IIT-R campus. The system can treat 7 m3 of sewage per day. The outlet from Johkasou is routed to a tertiary unit consisting of a Pressure Sand Filter and an Activated Carbon Filter for additional treatment. The effectiveness of removing organic and nutrient waste, the system's ability to function under various stress circumstances, and the performance of Johkasou at low sewage temperatures were all factors assessed during the study. Results showed that the Johkasou system effectively treated the wastewater generated at IITR. The system's average effluent concentration for biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), and total nitrogen (TN) was 9 mg/L, 24 mg/L, 8 mg/L, and 8.7 mg/L respectively. In order to find the ideal poly aluminum chloride (PAC) dosage for the successful removal of total phosphorous, we performed a jar test study with different dosing. We examined how well PAC dosing enhanced total phosphorous (TP) removal in Johkasou. The findings demonstrated that the total phosphorous in the effluent was removed below 1 mg/L at an ideal PAC dosage of 200 ppm. We concluded from the vacation stress analysis that the system approximately requires a recovery time period of about 48-72 hours to stabilize when there is no influent for eight consecutive days. From the functional stress analysis, we concluded that we could turn the blower off for around 4-6 hours a day without impacting the system's performance. This will contribute to a 25% reduction in electricity costs. Another study was conducted in which the system was fed with sewage for approximately three months, with temperatures varying from 16-20 °C with three different HRTs of 22, 26, and 31 hours. The results showed that increasing the HRT from 22 to 31 hours when the sewage temperature varies from 16-20 °C significantly improved COD, BOD, TSS, and TN removal efficiency. The removal efficiency of COD and BOD increased from 88% to 94% and 87% to 97%, while TSS and TN removal efficiency increased from 88% to 96% and 60% to 79%, respectively. In order to obtain the kinetic coefficients, three kinetic models, the first-order, second-order, and Stover-Kincannon Model, were applied to the system. The optimal HRT for the Johkasou system, when the sewage temperature varies in the range of 16-20 °C, was 31 hours. In comparison, for temperatures in the range of 24-27 °C, Johkasou can be operated at 22 hours HRT, providing the highest removal efficiency for all the parameters tested. Johkasou's experimental data were used in substrate removal models to determine the rate of change in COD and TN concentrations. This study observed that the second-order substrate removal model fits well for COD with R2 = 0.9882, and Stover-Kincannon Model fits well for TN with R2 = 0.9703. Based on the kinetics analysis, the performance of the reactor can be optimized. It also offers the system's reaction rate and serves as a foundation for reactor design and operation. The wastewater treatment cost is Rs 23/m3, including electricity, cleaning and maintenance, chemical, and desludging costs. Overall, the research points to the Johkasou system as a viable option for decentralized wastewater treatment, particularly in locations with restricted access to centralized treatment facilities.