Sewage farms and constructed wetlands: Treatment Potential of Sewage Farms and Constructed Wetlands for Domestic Sewage

This thesis analyses the working of sewage farms and brings out its similarities with constructed wetlands in its functioning as a low-cost waste treatment and resource recovery facility. A mathematical model is developed for evaluating the treatment potential of sewage farms/constructed wetlands for the BOD removal by assuming it as made up of a number of continuous flow stirred tank reactors (CFSTRs) in series. In order to improve the accuracy of predictive equations, provisions were made to take into account the effect of evaporation and evapotranspiration losses. The proposed model was validated against measured values of BOD removal from a constructed wetland at Listowel, Canada (summer) and compared with the simulated results using the other models such as USEPA (1988), Chen et al. (1999) and Vogeler and Scherfig (2000). In order to further ascertain the validity of the proposed model it is applied for the sewage farm froma a typical south Indian city of Madurai. In the light of the available literature and the findings from the present study, a design procedure and guidelines are proposed for the design of sewage farms/constructed wetlands at the end of the study.