低温污水前置强化混凝

Enhanced Coagulation as a Pretreatment for Low Temperature Wastewater

研究低温对强化混凝过程的影响,合成新型复合混凝剂(Synth A),利用膜分离分级、三维荧光光谱(3DEEM)和紫外差异分析等技术研究常温、低温(2~5℃)条件下强化混凝对溶解性有机物、溶解性有机氮等的去除特征及其对后续生物处理的影响.结果表明,常温下氯化铝(AlCl_3)、聚合氯化铝(PACl)和Synth A混凝后浊度去除率和颗粒态COD、N去除率,胶态COD、N去除率高度相关;与相应溶解态指标关系不明确.混凝对溶解性有机物荧光响应值的去除率远高于溶解态COD的去除率.溶解性有机氮(DON)是除颗粒氮(PN)和胶态氮(CN)外,前置混凝分离去除总氮(TN)的主要部分.低温对强化混凝的影响主要体现在,低温抑制上述3种混凝对浊度和COD去除,且抑制程度依次为AlCl_3>PACl>Synth A;低温对颗粒态、胶态和溶解态COD、N的混凝去除效果产生不同程度的影响,且对颗粒态和胶态COD、N的负面影响较大.低温原水溶解性有机物荧光响应值较常温原水大幅度升高.低温混凝对荧光响应值及紫外差异吸收的影响较常温更为显著.低温条件下,Synth A对TN、DN及DON的去除率较常温略有提高,保持了对PN和CN的去除能力,投量为30 mg·L-1以上时,DON去除率约为28.5%~41.7%,而常温仅为17%~31.4%.采用前置混凝分离去除大量COD和一定量的TN,能大幅减少曝气池停留时间,稳定TN控制效果.因而冬季采用Synth A等低温适应性强的混凝剂强化前置混凝可以在一定程度上弥补生化效率降低,缓解脱氮压力,稳定处理效果.

The effects of low temperature on enhanced coagulation were studied. A new composite coagulant called Synth A was synthesized. The effects of enhanced coagulation on the removals of dissolved organic matter,dissolved organic nitrogen,and so on under room temperature or low temperature（ 2-5℃） were determined,and their influences on biological treatments were investigated by using membrane fractionation distribution, three-dimensional fluorescence spectrum（ 3 DEEM）, and differential ultraviolent absorbance. The results showed that,under room temperature,the removals of particulate COD,particulate nitrogen,colloidal COD,and colloidal nitrogen were highly correlated with turbidity reduction by coagulation using aluminum chloride（ AlCl3）,poly aluminum chloride（ PACl）,and Synth A as coagulants separately,while the relationship was not clear between the dissolved parameters and turbidity reduction. The reduction of fluorescence value of dissolved organic matter after coagulation was much higher than that of dissolved COD. Dissolved organic nitrogen（ DON） is removed to the greatest extent by preset coagulation along with particulate nitrogen（ PN） and colloidal nitrogen（ CN）. Low temperature affected enhanced coagulation in many aspects. It inhibited turbidity reduction and COD removal by the three coagulants with the order being AlCl3 PACl Synth A. It exhibited differential influences on the removals of particulate,colloidal and dissolved COD,and nitrogen,and it showed greater adverse effects on particulate and colloidal COD and nitrogen. The fluorescence value of dissolved organic matter in low temperature water showed a significant increase,and its reduction by coagulation was high,compared with that in room temperature water. Low temperature coagulation exerted greater impacts on ultraviolet differential absorbance than did room temperature. Under low temperatures,slight increases of total nitrogen（ TN） removal,DN,and DON removals were achieved by using Synth A as coagulant,and removals of PN and CN were maintained,compared with room temperature. As an example,when Synth A dosage was above 30 mg·L-1,DON removal reached 28. 5%-41. 7%at low temperature,while the removal was only 17%-31. 4% at room temperature. A large portion of the COD and some TN were removed by coagulation as a pretreatment,indicating that a large amount of the time in an aeration pond could be reduced,and the removal efficiency of TN would be stabilized. Therefore,in winter,the decrease of biological treatment efficiency could be alleviated to some extent by using enhanced coagulation with an adaptable coagulant,such as Synth A as a pretreatment,which would relieve the stress of denitrogen and stabilize treatment efficiency.