Effect of organic acid on heavy metals removal from sewage sludge

The effect of different organic acid on heavy metals removal from sludge was investigated. It indicated that the inhibition of various organic acids on heavy metals removal was substantially discrepant. To different heavy metals, the sensitivity of effect extent was followed as Pb>;Cu>;Zn. The organic acid with two carbonyls had no negative effect on the growth of sulfur-oxidizing bacteria. As to the organic acids with single carboxyl and with similar configuration, the negative effect on heavy metals removal increased with the increase of the length of carbochain. The effect of aromatic organic acid on heavy metals removal was not significant as that of the organic acid with low molecular normal chain. Organic acid with low molecular weight and single carboxyl could significantly stimulate the TN and TK loss from sludge during heavy metals removal, while the TP was not affected because of good relativity between its solubilization and sludge pH. Oxalic acid and benzoic acid had no obvious effect on the release of nutrients from sludge.