富镁C3A体系下鸟粪石结晶法和LDHs法对养猪沼液中氨氮、磷及有机物的协同去除

Ammonia nitrogen, phosphorus and organic pollutants are riched in anaerobically digested piggery wastewater. So far large-scale pig farm drainage still have damaged environment due to lack of econimical and facultized treatments for removal these contaminants up to emissions standards. MAP method can efficiently remove ammonia nitrogen and phosphorus, and LDHs method can treat with organic pollutants greatly, yet either methods using in anaerobically digested piggery wastewater does not meet the practial demand of standard. The combination of MAP and LDHs with magnesium-rich C3A is expected to achieve a breakthrough technology for ammonia nitrogen, phosphorus and organic pollutants in anaerobically digested piggery wastewater. The aims to find out the control mechanism for synthesized magnesium-rich C3A is choosed appropriate treatment process for these pollutants. The dissoluted compounds and dissolution rate from magnesium-rich C3A during reactions in actual and simulated wastewater were investigated to discuss reaction mechanisms and control mechanism by the combination of MAP and LDHs methods, such as crystallizations, ion exchange, surface chemical precipitation and organic adsorption with distribution. And the competitive adsorption behavior and its control mechanism of NH4+、PO43- ions and organic pollutants would be revealed in the hydration process of magnesium-rich C3A forming magnesium ammonium phosphate and calcium-based materials. The reactions products contained nitrogen and phosphorus referred to above could recovery as slow-release organic fertilizer, and there is no secondary pollution. It could provide instructions for disposing NH4+、PO43- ions and organic pollutants from wastewater to meet emissions standards by using cement-based materials, and also it could offer theoretical basis for resource utilization from solid wastes containing Ca, Mg, Al elements.

养猪沼液富含氨氮、磷和有机物，迄今尚缺经济实用的处理技术使其达标排放，规模化养猪场排水污染严重。鸟粪石结晶法可高效去除氨氮、磷,LDHs 法可大量去除氨氮、有机物，仅用一法处理沼液皆不能达标排放。富镁 C3A 投入沼液可使鸟粪石结晶法和 LDHs 法协同作用，有望实现沼液处理技术突破。本项目拟搞清富镁 C3A合成的控制机制，以优选合成工艺使其最宜于沼液处理；研究投入沼液和模拟沼液中富镁C3A组分的析出形式及速率，探寻鸟粪石结晶法和LDHs法作用时的各种化合结晶、离子交换、表面吸附、有机物分配吸附、沉淀析出等作用及其控制机制；搞清富镁C3A投入沼液后氨氮、磷及有机物去除竞争机制、其它组分影响机制。容纳污染物的产物可做氮、磷缓释的有机肥回收，无二次污染。本研究可为富镁C3A体系处理养猪沼液提供指导，以经济、有效地实现沼液达标排放；可拓宽水泥基材料在污染控制领域应用，为含钙镁固废资源化提供指导。

养猪沼液多存在氨氮、磷和有机物超标问题，迄今尚未有经济、实用的技术深度处理养猪沼液使之达标排放，制约了养猪行业的集约化和规模化发展。本项目依据材料原位合成-污染物自净化的水处理思路，以养猪沼液氮磷及有机物深度处理为目标，通过在水泥基材料铝酸三钙（C3A）中添加镁源制备出富镁C3A，将其投入沼液中，利用鸟粪石结晶法协同LDHs法高效去除氨氮、磷及有机物，实现沼液中氮、磷及有机物的达标排放。本项目研究成果主要包括以下四个方面：1）采用固相反应法成功制备富镁C3A，且富镁C3A由部分镁取代C3A形成的Ca3-xMgxAl2O6和游离MgO两部分组成。2）探讨了LDHs法对氨氮、有机物的去除效果及其去除机制。LDHs法对NH4+的去除量达到155.4 mg·g-1，主要是C3A水化产生的大量OH-与少量Al(OH)4-与NH4+发生中和反应；通过层间阴离子交换去除阴离子型有机污染物，吸附量达4.5 mmol·g-1，且副产物为有机LDHs。此外，为富镁C3A对沼液中有机物的去除产物资源化再利用提供指导，本课题还考察了有机LDHs对非离子型的萘、阴离子型甲基橙及阳离子型有机物罗丹明B的去除，其吸附量分别为31.0、167.8与49.6 mg·g-1，且去除机制分别为分配作用、阴离子交换及表面吸附。3）探究了鸟粪石结晶法对氮磷的去除效果及其去除机制。鸟粪石结晶法对铵根和磷酸根的去除率分别为95.3%和11.7%，在溶液pH为8.0时镁离子与二者化学沉淀形成鸟粪石产物。4）研究了富镁C3A在模拟及实际沼液中对氨氮、磷酸根的去除效果及影响机制。模拟沼液中，铵根及磷酸根的去除量分别为44.5和21.6 mg·g-1，且鸟粪石与LDHs协同生长受pH影响：反应后溶液pH高于8.2时，鸟粪石与LDHs同步生长；溶液pH低于8.2时，鸟粪石优先结晶。实际沼液中，氮磷去除量分别为84.3和38.6 mg·g-1。本课题研究结果可为富镁C3A对养猪沼液的深度处理提供指导，以经济、有效地实现沼液达标排放，并进一步拓宽水泥基材料在污染控制方面的应用领域，为含钙镁铝固废的资源化利用指引方向。