Study on Precipitation Treatment of Ammonia Nitrogen in the Wastewater from Ethanol Production Using Cassava

Ammonia nitrogen in the wastewater from ethanol production using cassava was removed by precipitation method in the paper. It was studied that the varieties and dosages of precipitants, pH value and reaction time have an effect on removal of ammonia nitrogen. The experimental results indicated that the removal rate of ammonia nitrogen is able to reach 93.7% under the condition of a pH of 9, MgCI2·6H2O and Na2HPO4·12H2O as precipitants and 30 minutes of reaction time. The mole rate of Mg2+ / NH4+ / PO43is 1.4 / 1 / 1.2. Meanwhile the obtained precipitate NH4MgPO4·6H2O, also called struvite, could be made use of compound fertilizer. Introduction Excess discharge of ammonia nitrogen in the wastewater is a significant cause of eutrophication of water bodies. This kind of wastewater pollution to the environment have to be economically and effectively controlled, which is a problem that should be solved quickly for chemical industry and environmental protection industry. At present, there are many technical methods for treatment of ammonia nitrogen wastewater. Chemical precipitation method have attracted tremendous attention because of the short reaction time, simple technological process, high removal efficiency and reaction product magnesium ammonium phosphate (MAP) being able to used as controlled release fertilizer for recycle of ammonia nitrogen.[1, 2] Ammonia nitrogen in wastewater is removed by chemical precipitation method, in which precipitant Mg2+ and PO43reacts with NH4+ in wastewater to generate precipitate in the form of complex salt NH4MgPO4·6H2O known as struvite. Interiorly, there are precedents for the treatment of the high-concentration ammonia nitrogen wastewater using MAP precipitation method [3-6]. However, few research on the removal of ammonia nitrogen in the wastewater from ethanol production using cassava by precipitation method have been reported. In this paper, it have been studied that the high-concentration ammonia nitrogen wastewater from ethanol production using cassava as raw materials in a factory in Henan was treated by MAP precipitation method. Also, the conditions of removal of ammonia nitrogen in the wastewater were optimized and a satisfactory result was obtained finally. Experimental Materials The wastewater used in the experiment were obtained from a factory in Henan, in which applied cassava as raw materials for ethanol production. The water quality indexes of the wastewater and analytical techniques are shown in table 1.