Efficiency of constructed wetlands in treating E. coli bacteria present in livestock wastewater

Abstract

Constructed wetlands are artificial wetland units, designed for adopting the principle of natural wetlands for purifying wastewater. Well-designed and well-constructed wetlands play an important role not only in reduction in organic compound/impurities, but also in coliform reduction in wastewater. The three small laboratory-scale units were control, Typha and plant species design based on USEPA procedure. The plant species are watered for a few days to promote their stable growth. Then, the three wetland units were seeded with livestock wastewater from a nearby cattle farm. Qualitative analysis by polymerase chain reaction and quantitative analysis are carried out by doing microbial culture in selective medium of MacConkey agar. The E. coli load is monitored before and after treatment in all the three units with different trials. It is found to be at a higher level in Typha unit after 24 h than in mixed and control units. The sample from the bottom of the constructed wetland unit is withdrawn and cultured for five days, and the bacterial load is found to be 9 × 104. Meanwhile, considerable reduction is observed in the Typha wetland unit after 5 days, and the bacterial load is 4 × 102. Mixed species wetland shows excellent treatment efficiency, and the bacterial load (E. coli) is very less after 5 days. It is evident from the study that constructed wetlands are effective in the treatment of E. coli bacteria wetland plants which are used for treatment.