Effects of seasonal temperature variations on the modifications of phosphates in wastewaters
The presence of phosphorus is undesirable in treated wastewater effluents as it leads to eutrophication in the lakes or river systems. Municipal wastewater treatment plants should therefore give particular attention to keep total phosphate concentrations below 1 mg/l in their effluents. Phosphorus can be removed by biological methods up to about 40 % of its influent concentration. Bacteria hydrolyse and convert the condensed phosphates in to the easily removable orthophosphate form. Temperature variations of air and wastewater can have significant influence on the form of phosphate fraction present in wastewater. In the present study, the effects of temperature variations in summer and winter on the relationships between filterable orthophosphates and total phosphates in wastewater are reported. Using results from laboratory studies as well as from existing wastewater treatment plants treating domestic wastewater, simple mathematical models are developed for various phosphate species. These relationships are useful in day-to-day operation of a treatment plant in monitoring the total phosphates leaving with the treated effluent : if orthophosphate measurement is utilized to characterize the effluent total phosphate, then the plant operator will be well advised to watch the seasonal variations of the various phosphate concentrations.