基于单质硫回收的同步生物脱氮除硫工艺研究

The simultaneous biological sulfide and nitrate removal process is a novel process which can oxidize sulfide to sulfur with nitrate as electron accepter under anoxic conditions. Many researchers have observed the production of elemental sulfur throughout the study, and paid more and more attention to the problem of sulfur recovery in this novel process. Up to now, most of the studies still remain to obtain elemental sulfur production on the basis of sulfur mass balance calculation, which can not accurately provide the amount of recovered sulfur in the effluent; and the characteristics of elemental sulfur produced in this system need further study. Taking the simultaneous biological sulfide and nitrate removal process under autotrophic condition as research object, the project discusses process performance, characteristic of elemental sulfur and model optimization of the process, which aims to improve the recovery of elemental sulfur. The substrate conditons are optimized in order to elevate the production of observed elemental sulfur; Consequently, operation conditions are regulated in order to reduce sulfur deposition on the surface of sludge, thus further to improve the yield of elemental sulfur in the solution; Furthermore, the characteristics of elemental sulfur in the process are carried out, such as morphological feature, distribution patten and chemical property;Combined with the neural network system, a mathematical model is eatablished with the recovery of elemental sulfur in the effluent as an indicator, which could provide references for elemental sulfur recovery in the novel process.

同步生物脱氮除硫工艺是指在缺氧状态下，以硝酸盐作为电子受体生物氧化硫化物的工艺。在研究过程中，不少研究者观察到单质硫的产生，且对该新型工艺中的单质硫回收问题愈加关注。迄今为止，绝大部分研究仍停留在通过硫质量平衡计算获得单质硫产量，无法精准判断出水中可回收的单质硫量，且该系统中产生的单质硫特性等问题仍有待深入研究。本项目以自养型同步生物脱氮除硫工艺为研究对象，以单质硫回收为目标，从工艺性能、单质硫特性及模型优化三方面展开研究：优化同步生物脱氮除硫工艺的基质条件，提高系统中表观单质硫产率；调控同步生物脱氮除硫工艺的运行条件，减少硫元素在污泥表面沉积，进一步提高反应液中单质硫回收率；开展同步生物脱氮除硫工艺中单质硫特性研究，解析该体系中单质硫的形态特征，分布规律以及化学特性；并结合神经网络系统，以反应液中单质硫回收率为指标，建立同步生物脱氮除硫工艺的数学模型，为该新型工艺回收单质硫提供相关依据。

同步生物脱氮除硫工艺中不仅可同时去除水中硫素和氮素污染物，还可以回收单质硫，已成为环境工程领域的研究热点，但其存在产生单质硫缺乏精准测定和产量较低等难题，且单质硫特性有待深入研究。本项目针对上述问题，以单质硫回收为目标，从工艺性能、单质硫特性及模型优化三方面展开研究，可为该新型工艺回收单质硫提供理论依据和技术参数。主要结论如下：①探明了基质条件对同步脱氮除硫工艺单质硫产率的影响。基于Pearson相关性分析、主成分分析和电子守恒模型拟合结果，高进水基质浓度（480mg S/L），维持适当基质比例（5：2），且以亚硝酸盐作为氮素时，有助于提高该工艺的总单质硫产率；②探明了运行条件对同步脱氮除硫工艺单质硫产率的影响。基于主成分分析、模型拟合和响应面分析结果，适当进水pH（6.7±0.1），低水力停留时间（2h）和高循环比（30），有助于提高该工艺的反应液单质硫产率；③探明了同步脱氮除硫工艺产生的单质硫特性。该工艺产生的单质硫多为表面并不光滑的球状颗粒或不规则形状，反应液和污泥中单质硫主要元素组成为S、C和O，主要存在形式为环状S8晶体（斜方硫）。表面带负电荷,粒径呈正态分布。④构建了同步脱氮除硫工艺的人工神经网络模型，通过连接权重法、Garson算法和PaD方法明确影响单质硫回收率的主导因子，重要性顺序为：HRT>进水硝酸盐>S/N摩尔比>进水硫化物>pH。