鸟粪石结晶法去除某粮食发酵废水中磷的研究

由于某粮食发酵废水中NH_4~+、PO_4~(3-)、Mg~(2+)的物质的量比约为60∶3∶2,水质偏中性,水温适宜形成鸟粪石结晶沉淀(MgNH_4PO_4·6H2O),在厂区管道内积累了大量鸟粪石及其他类型的沉淀,阻碍了厂区对污水的正常处理。为了解决这个问题,采用鸟粪石结晶法去除该粮食发酵废水中的无机磷,在污水进入下一工艺前降低污水氮、磷负荷,回收反应得到的沉淀物。采用单因素法研究了pH值、镁盐对鸟粪石结晶法去除此粮食发酵废水中无机磷效果的影响。结果表明,以MgCl_2·6H_2O为镁盐,控制废水终点pH=9,n(Mg)∶n(P)=1.38,在正常水温下以100 r/min搅拌反应20 min,无机磷从100 mg/L降至7.75 mg/L,去除率达92.25%,氨氮质量浓度从499.67 mg/L降低至398.11 mg/L,去除率达20.38%。对试验得到的结晶沉淀物进行了定量与定性分析,结晶沉淀的主要成分是晶型结构较好的鸟粪石沉淀,鸟粪石纯度可达89.14%。

On the phosphorus removal from a food fermentation sewageby struvite crystallization

In this paper,the authors would like to devote their study focus on the effect of pH value and different magnesium salt contents on the removal efficiencies of the inorganic phosphorus in the food fermentation sewage by struvite crystallization with a single-factor functioning method.As is known,under certain conditions,such as under the function of neutral pH value,proper sewage temperature and the mole ratio of NH4+ ∶ PO43-∶ Mg2 + (ie.,60 ∶ 3 ∶ 2),it is possible for the struvite precipitation (MgNH4PO4 · 6H2O) and other kinds of sedimentation to take place in the food fermentation sewage in the pipes.And,in turn,enormous amount of precipitation is likely to lead to the breakage of sewage treatment process.To solve the problem caused by the blockage in the pipelines,the paper would like to propose a method of struvite crystallization to remove the inorganic phosphorus from such sewage so as to reduce such inorganic phosphorus and ammonianitrogen and promote the recycling process before such food fermentation sewage turns into the next process.The results of our experimentation indicate that it has been made possible to reduce the inorganic phosphorus and ammonia-nitrogen content rate effectively from 100 mg/L to 7.75 mg/L and 499.67 mg/L to 398.11 mg/L,respectively, and in turn to make the removal efficiency increase by 92.25％ and 20.38％ on the condition when the pH value keeps at 9,with the magnesium salt of MgCl2 · 6H2O,the mole ratio between PO43-and Mg2+ being 1 ∶ 1.38,and the agitation rate being 100 r/min,and the reaction time-20 min at the normal water temperature.And,consequently,the quantitative and qualitative analysis of the precipitations gained from the experiments prove that the main composition of the precipitations is the struvite precipitation which remains a typical crystal structure.The purity of the resulted struvite precipitation has been found up to 89.14％,which is still feasible for further struvite crystallization to remove the inorganic phosphorus from the food fermentation sewage.Thus,it can be seen that the problem of pipe-blockage can be solved easily and the inorganic phosphorus and ammonia-nitrogen can be made recovered from the aforementioned food fermentation sewage.