and in the presence of C.esculenta plants, increased from 1 (on day 1) to approximately 1.2 (on day 5) and from 1 (on day 15) to approximately 1.6 (on day 20). This indicated that the latter part (run 4) of the experiment IV was more efficient than the earlier part (run 1). A similar trend was observed in the rest of the experiments also. As mentioned earlier, the planted raceways have performed with better COD removals than the controls, for example, in experiment IV on day 5, COD level dropped from its initial 1650 to 213mgl−1 (87.1% removal) in the presence of plants. In controlled raceways, the removal was 84.2%.