Meena Kumari Sharma

Modified septic tank-anaerobic filter unit as a two-stage onsite domestic wastewater treatment system

This study demonstrates the performance evaluation of a uniquely designed two-stage system for onsite treatment of domestic wastewater. The system consisted of two upflow anaerobic bioreactors, a modified septic tank followed by an upflow anaerobic filter, accommodated within a single cylindrical unit. The system was started up without inoculation at 24 h hydraulic retention time (HRT). It achieved a steady-state condition after 120 days. The system was observed to be remarkably efficient in removing pollutants during steady-state condition with the average removal efficiency of 88.6±3.7% for chemical oxygen demand, 86.3±4.9% for biochemical oxygen demand and 91.2±9.7% for total suspended solids. The microbial analysis revealed a high reduction (>90%) capacity of the system for indicator organism and pathogens. It also showed a very good endurance against imposed hydraulic shock load. Tracer study showed that the flow pattern was close to plug flow reactor. Mean HRT was also found to be close to the designed value.

Effect of physical property of supporting media and variable hydraulic loading on hydraulic characteristics of advanced onsite wastewater treatment system.

A laboratory-scale study was carried out to investigate the effects of physical properties of the supporting media and variable hydraulic shock loads on the hydraulic characteristics of an advanced onsite wastewater treatment system. The system consisted of two upflow anaerobic reactors (a septic tank and an anaerobic filter) accommodated within a single unit. The study was divided into three phases on the basis of three different supporting media (Aqwise carriers, corrugated ring and baked clay) used in the anaerobic filter. Hydraulic loadings were based on peak flow factor (PFF), varying from one to six, to simulate the actual conditions during onsite wastewater treatment. Hydraulic characteristics of the system were identified on the basis of residence time distribution analyses. The system showed a very good hydraulic efficiency, between 0.86 and 0.93, with the media of highest porosity at the hydraulic loading of PFF ≤ 4. At the higher hydraulic loading of PFF 6 also, an appreciable hydraulic efficiency of 0.74 was observed. The system also showed good chemical oxygen demand and total suspended solids removal efficiency of 80.5% and 82.3%, respectively at the higher hydraulic loading of PFF 6. Plug-flow dispersion model was found to be the most appropriate one to describe the mixing pattern of the system, with different supporting media at variable loading, during the tracer study.

Substrate Removal Kinetics of Domestic Wastewater Treatment in a Two-Stage Anaerobic System

An investigation was done on the process kinetics of a two-stage (modified septic tank plus anaerobic filter) anaerobic bioreactor while treating actual domestic wastewater. The individual values of second-order substrate removal rate constant (k) for septic tank and anaerobic filter were observed as 0.36 and 0.26 per day, respectively. It was 0.49 for the combined system. The maximum removal rate constant (Umax) and saturation value constant (KS) were 737 and 934 mg/L/d, respectively, for anaerobic filter when the modified Stover-Kincannon model was applied to this part of system. Both the second-order and the modified Stover-Kincannon models exhibited high correlation coefficents (R2 = 98-99%).

Operation and maintenance of sewerage systems: present challenges and possible solutions—an Indian experience

A strong focus on increasing gross domestic product to meet demanding needs stretched the country on the brink of overstretching the ecological carrying capacity. Unfortunately, rivers are among th...