Impact of Controlling Different Kinds of Waste Sludge with Acid and Alkaline on Release of Ammonia and Phosphate

pH was controlled to 3.0 or 10.0, with pH uncontrolled as blank, to study the release of ammonia and phosphate for different kinds of waste sludge, namely primary sludge (PS), waste activated sludge (WAS), and mixed sludge (MS) composed of PS and WAS at a ratio. The results show that acidity and alkalinity has different effects on different kinds of sludge at room temperature. When the pH is controlled to 10.0, it is observed that ammonia for PS and WAS is rapidly released to the top, 6.53mg/g TS and 8.40mg/g TS on the 4th day. But from the peak value on, the release amount shows downward until the experiment period ends. At pH 3.0 the release amount for PS is little, even less than the blank test, while the release amount for WAS is higher at pH 3.0 in all the period, and arrives at the maximum 10.07mg/g TS on the 6th day, after which the values keep relatively stable. Compared with the release of ammonia, the changes of release amount of phosphate is similar to the two kinds of waste sludge mentioned above, acidity>alkalinity>blank test ,and the amount at pH 10.0 is close to the blank test. Because of high percentage of PS, the release law of ammonia for MS is similar to PS. The order of release amount is as follows: alkalinity>blank test>acidity, but PS is different , the release amount at pH 10.0 always keeps rising until the period ends. The release of phosphate is consistent with the PS and WAS except that it is inhibited under alkaline condition.