摘要
利用超声波对剩余污泥进行破解,可以促使污泥胞内外物质溶出进入液相,既能促进后续污泥的厌氧水解酸化,还有可能形成新的污泥减量工艺。目前国内外破解污泥大多采用声能密度为0.096 W/mL至2 W/mL的超声波,声能密度较高能耗也较大,在实际工程中难以推广。本文采用25 kHz、0.05 W/mL的较低声能密度的超声波破解加碱后的剩余污泥,研究破解对后续厌氧酸化的促进作用,并探索将酸化后的污泥回流至曝气池进行隐性生长实现污泥减量的可能性。
实验结果表明,污泥经加碱超声波破解后,污泥SCOD溶出率随着加碱量和超声波作用时间的增加而增加。厌氧酸化过程中,对照组总VFAs产量一直处于较低水平,而经预处理后的污泥最大产酸量集中出现在厌氧酸化的第48～88 h,说明加碱后超声波破解对污泥厌氧水解酸化有较好的促进作用。
剩余污泥酸化后重新回流入曝气池进行隐性生长,可以实现污泥的减量。污泥酸化-好氧减量工艺在30 d的运行中,除了取样分析,基本没有外排剩余污泥,而对照组在此期间共排放干污泥86.1 g。酸化污泥重新回流入曝气池后使测试组进水COD平均值比对照组增加147%,氨氮增加32%,TP增加294%,系统出水TP值成倍增加,需考虑污泥酸化液除磷的问题。酸化污泥回流后使测试组曝气池混合液污泥浓度平均值增加725 mg/L,VSS/SS值比对照组低。长时间的运行后,污泥减量系统内的污泥微生物活性有所下降,建议每隔一定时间对其进行少量排泥,以保证微生物活性。
Ultrasonic can be applied to disintegrate the waste activated sludge(WAS), so that the substances inside and outside the cells release into the liquid phase. After disintegration, the rate of subsequent anaerobic hydrolysis and acidification was improved and a new excess sludge reduction process may be found. At present, ultrasonic densities ranging from 0.096 W/mL to 2 W/mL was the most commonly applied method used for sludge disintegrate. However, higher ultrasonic density resulted in higher energy consumption, which made it’s hard for practical engineering applying. In this paper, ultrasonic with relatively lower density (25 kHz, 0.05 W/mL) was employed to disintegrate the sludge that alkali was added in before. The promoting effects of disintegrate to sludge hydrolysis and acidification with the possibility of recycling the acidified sludge to the aeration bank to realize sludge reduction based on the lysis growth were studied.
It has been found that the soluble chemical oxygen demand (SCOD) leaching rate increase with the alkali amount and ultrasonic disintegration time. During the procedure of anaerobic hydrolysis and acidification, the control total volatile fatty acids(VFAs) production has been at a low level, while with proper pretreatment the VFAs concentration came to the highest mostly after 48 to 88 hours, demonstrated that ultrasonic disintegrate after adding alkali have well promoting effect on sludge acidification.
Excess sludge reduction process based on the lysis growth can be realized by recycling the acidified sludge back to the aeration tank. Acidification-aerobic sludge reduction process operated stably 30 d without any sludge discharging except sampling analysis however; the control discharges 86.1 g dry sludge during this period. The recycling of acidified sludge increase the average COD、ammonia nitrogen and total phosphorus(TP) by 147%、32% and 294%, respectively;and, a duplicated total phosphorus vaule in effluent was observed, phosphorus removal form acidified sludge should be considered. Recycling of acidified sludge increase the sludge concentration in the aeration tank by 725 mg/L. After a long time operation, the microorganism’s activity in the sludge reduction system declined. It’s suggested that some sludge is discharged for a certain time to keep the activity of microorganisms.
引文
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