摘要
低C/N生活污水的有机物含量偏低,不能满足常规工艺的脱氮、除磷的碳源要求,致使脱氮、除磷的效果不理想。因此提高低C/N生活污水的脱氮除磷效率成为目前研究的热点问题之一。本文主要是寻找一种针对低C/N生活污水有效的生物脱氮方法。
本文采用活性污泥吸附低C/N生活污水中的有机物,然后利用澄清池使活性污泥及其吸附的有机物从污水中分离出来,经过碳源形态转化,再投入反硝化过程,为反硝化提供碳源,以达到脱氮的目的。
首先,进行了原水中系统碳源利用途径的研究,发现厌氧活性污泥对COD的吸附率能达到70%以上;而对NH_4~+-N几乎没有吸附效率,最高仅达到5%。运用厌氧污泥对生活污水进行吸附,可以达到对污水进行碳氮分离的目的。然而,活性污泥吸附有机物后,进行脱附试验发现无论是在搅拌、加次氯酸钠溶液还是进行水解酸化的条件下,活性污泥所吸附的有机物都较难脱附下来。脱附的有机物占其所吸附有机物总量的比例较少,不超过25%。
其次,考察了澄清池用于活性污泥吸附有机物后的碳氮分离情况,发现澄清池可以较好进行泥水分离,从而实现碳氮分离。通过碳氮分离可以吸附污水中大约50%的COD,而对NH_4~+-N几乎没有吸附,平均吸附率为仅4.0%。
再次,对系统硝化性能的研究发现,运用活性污泥吸附进水中的有机物后,可以较大幅度地提高曝气生物滤池的硝化效果,使曝气生物滤池出水NH_4~+-N全部降到5mg/L以下。而由于厌氧活性污泥吸附有机物时携带了一部分NH_4~+-N,导致沉淀池出水NH_4~+-N浓度较高,然后在沉淀池后又加了一级曝气生物滤池,使出水NH_4~+-N降低到5mg/L以下。
最后,研究了反硝化的影响因素及系统缺氧池反硝化效果,发现利用厌氧活性污泥吸附进水中的有机物作为反硝化的碳源,可以取得较好的反硝化效果,经过3h的反硝化反应,出水的NO_3~--N的浓度降低到1mg/L左右。
本文成功运用厌氧活性污泥吸附进水中的有机物,然后利用这些吸附的有机物作为反硝化的碳源,解决了低C/N生活污水生物脱氮的碳源不足问题,取得了较好的脱碳效果,使出水NH_4~+-N和TN浓度达到GB18918-2002一级A的标准。
这种方法既减少了进入硝化过程中的有机物,提高了硝化效率,又为反硝化提供碳源,解决了低C/N生活污水生物脱氮的碳源不足的问题,还大量减少了剩余污泥量,节约了污水处理的成本。
As low C/N domestic wastewater contains less organic contents, we can’t get ideal results if we use the traditional nitrogen and phosphorus removal technology to remove nutrient. So how to improve the effect of nitrogen and phosphorus removal of low C/N domestic wastewater has been one of the hottest issues currently. And this paper presented an effective method of biological nitrogen removal that works in low C/N domestic wastewater.
We used activated sludge to adsorb the organic matters in the low C/N domestic wastewater, and then the clarification pool was used to separate the activated sludge and the adsorbents from wastewater. Thus the organic matters the activated sludge adsorbed which had been changed were input to denitrification process as carbon source in order to obtain the aim of denitrification.
Firstly, we researched the utilization pathway of the system carbon source from raw water. We found that anaerobic activated sludge could absorb COD more than 70%, but nearly no NH_4~+-N (the highest percentage was only 5% ) could be absorbed. If we used the anaerobic activated sludge to absorb low C/N domestic wastewater, carbon and nitrogen in the raw water would be separated effectively. But the desorption was not very easy. It was very difficult to separate the absorbed organic matters from the activated sludge, no matter to stir or add sodium hypochlorite solution or hydrolyze acidification. At last, the ratio of desorption/absorption was less than 25%.
Secondly, we investigated the clarification performance of carbon and nitrogen separation after the activated sludge adsorbing the organic matters. Results showed that the clarification pool could separate the activated sludge and the water to complete carbon and nitrogen separation. 50% of the COD could be adsorpted through carbon and nitrogen separation, while almost no NH_4~+-N could be adsorpted with average 4.0% removal of NH_4~+-N.
Thirdly, the performance of BAF nitrification was greatly improved after using activated sludge absorbing the organic matters in the influent, the concentration of NH_4~+-N in the effluent decreased to less than 5 mg/L. When the anaerobic activated sludge adsorbing organics, it carried a part of NH_4~+-N, causing the NH_4~+-N of the sedimentation tank effluent to be higher. Then another BAF was added fter the sedimentation tank, then the final effluent NH_4~+-N reduced to 5mg/L and reached the first-grade A standard.
Finally, the factors of denitrification and the effects of denitrification in anoxic bank were studied. Results showed that using the organic matters adsorbed by anaerobic activated sludge from low C/N domestic wastewater as denitrification carbon source could get a better effect of denitrification. The efflent NO3--N concentrations reduced to 1mg/L after 3h’s denitrification in the anoxic bank.
In a conclusion, using the organic matter adsorpted by anaerobic activated sludge from low C/N domestic wastewater as denitrification carbon source could completely solve the problem that biological nitrogen removal didn’t have sufficient carbon source of low C/N sewage, and the final effluent NH_4~+-N and TN reached the GB 18918-2002 first-grade A standard.
Using this method could supply carbon source for denitrification and reduce sludge production and save the cost of sewage treatment. Simultaneously, the organic matters of influent in nitrification process was reduced while the nitrification effect was improve.
引文
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