Decline of phosphorus, copper, and zinc in anaerobic swine lagoon columns receiving pretreated influent

ABSTRACT Land application of both anaerobic lagoon liquid and sludge can increase nutrient accumulation beyond the soil’s assimilative capacity and become a threat to water quality in regions with intensive, confined swine production. In a 15-month meso-scale column study, we evaluated the effect of manure pretreatment on the reduction of total suspended solids (TSS), total phosphorus (TP), soluble reactive P (SRP), and total copper (Cu) and zinc (Zn) in swine lagoons using (i) enhanced solid-liquid separation (SS) and (ii) solid-liquid separation plus biological nitrogen treatment with nitrification-denitrification (SS + NDN). A conventional anaerobic lagoon treatment was included as a control. A mass flow balance revealed that with both pretreatments the net mass input of TP, Cu, and Zn in the lagoon columns declined 80 to 100 % when compared to the control. Even though both pretreatments significantly reduced P in the inflow, TP and SRP were negatively correlated (r = -0.51 to -0.87) with TSS in the liquid fraction because of the dissolution of P from sludge into the overlying lagoon liquid. On the other hand, the removal of solids by both pretreatments effectively reduced Cu and Zn concentrations in the lagoon liquid, and their concentrations were positively correlated (r = 0.79 to 0.90) with TSS. The decline in mass accumulation of TP, Cu, and Zn in sludge as a result of the reduction of input solids can help minimize both the frequency of sludge removal for lagoon maintenance and the land area for its disposal.

摘要 在集约化密闭式生猪养殖区域，厌氧塘沼液与污泥的土地还田操作可能导致养分积累超出土壤消纳能力，进而对区域水环境质量构成威胁。本研究依托为期15个月的中尺度柱试验，评估了两种粪便预处理方式对生猪养殖厌氧塘中总悬浮颗粒物（Total Suspended Solids, TSS）、总磷（Total Phosphorus, TP）、可溶性反应态磷（Soluble Reactive Phosphorus, SRP）以及总铜（Copper, Cu）、总锌（Zinc, Zn）去除效果的影响：①强化固液分离（Enhanced Solid-Liquid Separation, SS）；②固液分离+硝化-反硝化生物脱氮（Solid-Liquid Separation + Nitrification-Denitrification, SS + NDN）。同时以常规厌氧塘处理作为对照组。物料衡算结果显示，相较于对照组，两种预处理方式均可使厌氧塘柱体中TP、Cu、Zn的净输入量降低80%至100%。尽管两种预处理方式均可显著降低进水总磷含量，但由于污泥中的磷溶解进入上层塘液，厌氧塘液相组分中的TP与SRP仍与TSS呈显著负相关（相关系数r=-0.51~-0.87）。另一方面，两种预处理方式通过固相去除，有效降低了塘液中的Cu与Zn浓度，且二者浓度与TSS呈显著正相关（相关系数r=0.79~0.90）。由于输入固相减少，污泥中TP、Cu、Zn的质量积累量下降，这有助于减少厌氧塘维护所需的污泥清掏频次，同时降低污泥处置所需的土地面积。