Role of sewage phosphorus in coastal water energy production

A study was carried out on the quantity and speciation of phosphorus in a sewage originating from Tuticorin town and discharging the contents in the Fishing Harbour area. Four prominent peaks were observed in the distribution of total phosphorus and during most of the months the concentration remained above 4 mgP/l. The annual mean contribution of total soluble phosphorus (86.73%) to total phosphorus was higher than that of particulate phosphorus (13.27%). Since all the chemical species of phosphorus are eventually converted into biologically utilizable form, the anticipated increment in energy production calculated from the stoichiometric composition of plankton [(CH₂O)₁₀₆(NH₃)₁₆H₃ PO₄] was to the tune of 1300 tonnes C/year. Assuming that all the three sewages of Tuticorin discharge comparable quantity of wastewater, the anticipated hike in primary energy synthesis was around 3900×10⁷ Kcal. Absence of frequent red tide in the bay indicated that the sewage water was diluted and displaced by coastal water current systems. Considering three trophic levels from phytoplankton production to fish production and an overall efficiency of 3.4×10^-3, the extra fish production due to sewage phosphorus was calculated as 132.60 tonnes/year. According to Winberg´s transformation the surplus production of energy due to the boosted fishery potential was around 132.6×10⁶ Kcal/year