Removal of Nitrogen and Phosphorus Compounds in the Waste Water of Food Processing Factories

Abstract

The waste water of food processing factories is usually treated with activated sludge, by which process nitrogen and phosphorus compounds were consumed by the sludge microorganisms.
However it has not been determined in detail what percentage of them are utilized by the sludge microorganisms with an excess of these compounds in the waste water. In this study, the waste water of a skim milk factory resolving various amounts of nitrogen and phosphorus compounds was treated with activated sludge. With the waste water of high N/P ratio, the resultant sludge had a high nitrogen content, whereas with the waste water of low N/P ratio it had a high phosphorous content. After the treatment, the water was left to settle for 24 hours and it was found that a part of the phosphorus compounds in the sludge was resolubilized into the supernatant, whereas the nitrogen compounds were reductionally decreased under anaerobic conditions. The phosphorous compounds in the supernatant of the waste water treated with activated sludge were clearly reduced when the chlorella was incubated in the supernatant for 6 days.
A flow sheet of the activated sludge system where the removal of the nitrogen and phosphorus compounds was incorporated was presented.