污泥酸化速率影响因子的探讨

采用城市污水厂污泥作为嗜酸微生物菌株来源,通过添加一定量的单质硫,使其中的嗜酸硫杆菌群大量增殖,并使污泥pH大幅降低.取得的培养物可用于废旧干电池中重金属沥滤等的处理.由于培养物对重金属沥滤效率和污泥的酸化速率密切相关,为此进行了不同的污泥种类、加硫量、污泥浓度和曝气强度对污泥酸化速率影响的实验.实验表明,初沉泥、二沉泥和混合浓缩污泥都能迅速利用硫产酸;加硫量(以100 mL污泥计)在0.5、1.0、2.0、4.0 g时,快速酸化的趋势相同.0.5 g的加硫量显示出略微慢的酸化速率,最后达到的最低pH在1.2左右,其他三个都降至1.0以下.污泥质量分数在0.5%、1.0%、2.0%、3.0%、4.0%时,也具有相同的酸化趋势,0.5%质量分数的污泥下降速率最快,这与较低浓度下污泥对pH的缓冲能力较小有关;曝气强度在0.45 L/min和0.3 L/min差别较小,5 d内能迅速降低pH,0.2 L/min的酸化速率较慢,足够长的时间(12 d)也能将pH降至2.5左右,0.1 L/min的曝气强度的酸化速率最慢,不能达到预期的酸化效果.

Factors affecting the sludge acidification rate

Indigenous thiobacilli,originated from sewage sludge and utilized elemental sulphur as the substrate,was employed in the study of sludge acidification rate,an important factor in bioleaching of heavy metals from spent batteries.Sludge type,sulphur amount,suspended solid(SS) concentration of the sludge,and aeration rate all affected the acidification rate.Cultures from primary sludge,secondary sludge and mixed sludge produced similar acidification rates.Results with more than 1 %(w/v) sulfur concentration were similar,while 0.5 % S was less effective.A low SS concentration resulted in a faster acidification rate;0.5%(w/w) concentration was the most effective of the five concentrations(up to 4%) studied.The aeration rates of 0.45 vvm(volume of air/vol of sludge in reactor/min) and 0.3 vvm were sufficient to lower pH to 2.5 in 10 days,while 0.2 vvm lowered pH to 2.7 in 12days;0.1 vvm resulted in a pH of 3.5 at the end of the test period.