Seasonal Variations of Phosphate Species in Wastewater

Abstract

Phosphates in wastewater occur as organic, ortho and polyphosphates. In biological wastewater treatment the total phosphorus concentration is reduced by about 20 percent due to bacterial action. It is known that the rate of biological activity in wastewater is affected by temperature. Similarly, significant variations in seasonal temperatures of both air and wastewater can have marked effect on the particular fraction of the phosphate species. Studies were conducted in an existing wastewater treatment plant to examine the phosphate variations from winter to summer. Results show an increase of about 30 percent in the ratio of total orthophosphates to total phosphates, in the effluent during summer compared to winter. Bacterial hydrolysis of polyphosphates during summer season could be responsible for this increase. From the studies, several simple correlations were established which may be useful in the day-to-day operation of a treatment plant. For example, by measuring the orthophosphate in the effluent, one can calculate the total phosphates using the defined relationship between the two.