Material balances of organics and nutrients in an oxidation pond

A series of experiments concerning a tertiary oxidation pond was performed from 10 January to 12 November 1979, using a model oxidation pond of 21 m² in capacity. The concentrations of organics and nutrients in influent and pond water were measured so as to consider the conversion of water quality in a tertiary oxidation pond. The sedimentation rates were measured weekly, and the final sediments were analyzed at the end of experiments, so that the material balances in respect to carbon, nitrogen and phosphorus were calculated and the various transition reactions were evaluated quantitatively. The result of the material balances showed that there were three main reactions in pond: the assimilation to algae; the sedimentation of suspended substance; and the decomposition of sediments. The regeneration rates of nutrients from sediments were so active that the removal of nutrients by algal solidification were not effective. Consequently, the overall removal efficiency of nutrients was 45% in total nitrogen and 43% in total phosphorus by a tertiary oxidation pond with 16 days detention time.