Efficacy of Rootzone Technology for Treatment of Domestic Wastewater: Field Scale Study of a Pilot Project in Bhopal. (MP), India.

Abstract

The urban water bodies in tropical developing countries are the worst victim of domestic wastewater / sewage, basically because of the widening gap between the increasing waste water generation and unavailability of commensurating economical resources to address the issue through conventional technologies. Hence, biological machines may prove to be a novel tool for sustainable management of water bodies. Rootzone technology being natural biological systems operating solely on solar energy is low cost and almost negligible operation and maintenance. The paper under reference therefore is an attempt to evaluate the performance efficiency of a field scale Horizontal Subsurface Flow constructed Wetland/Rootzone demonstration unit was constructed by Environmental Planning & Coordination Organisation (EPCO) at Ekant Park, Bhopal as an economically and ecologically viable pilot project. The unit is designed to treat 70,000 liters/day of wastewater of nalla passing through the park. The unit comprises of pretreatment (settling tank – 35 m 3) followed by Rootzone bed (700 sq.m) with gravels, Reed plants (Phragmitis karka) and inlet-outlet arrangements for sub-surface flow. To study the performance efficiency of the system physical-chemical and biological parameters of inflow and outflow water were monitored. Standard methods by APHA 1989 were followed for analysis. The average treatment performances were recorded monthly for 18 months after its installation (April 2002 to Sep 2003). The pollution removal efficiency of the system gradually increased and as the system stabilized to a large extent after 18 months the results clearly indicated removal efficiency of 100% for Organic Nitrogen, 98.7% for Coliform bacteria, 88.4% for Turbidity, 79.0% for TSS, 70.7 % for Total Solids, 71.2 % for TDS, 77.8 % for COD, 8.9% for TKN, 65.7% for BOD, 62 % for Nitrate Nitrogen, 53.3% for Ammonium Nitrogen. The treated water/ effluent’s D.O. levels increased by 139 % and reached 3.1 mg/l. indicating existence of aerobic conditions in the Rootzone bed. The treated water can be used safely for purposes like irrigation, aesthetic ponding, fish farming, washings, biodiversity etc. Results established that the overall removal efficiency of the system studied ranged from 65% to 90 % for various pollutants, besides being cost effective treatment technology.