沼液板式超滤膜预处理试验研究

如何降低超滤膜污染程度至最低状态是一项重要课题,为了最大限度地降低浓差极化的影响,通过试验将超滤工艺应用于沼液膜过滤法浓缩液体有机肥工艺,选取某养殖场内沼液,在不同压强下,观察不同压力时板式超滤膜的通量变化和污染物去除、截留情况。结果表明:在0.05～0.25 MPa压力下,板式超滤膜初期通量下降迅速,10～30 min后,膜过滤通量下降变缓并趋于稳定,这一过程与膜通量衰减经验公式吻合较好;板式超滤膜的通量随着压力上升而增高,但增幅逐渐降低,膜截留率与压力变化关系不大,膜对COD去除率较高,约70%,对NH_4~+-N、K~+等小分子物质去除率较差,仅22%～40%,小分子营养物质保留充足;滤出液营养指标为有机质营养0.16%,无机总营养0.217%,N-P_2O_5-K_2O比例为10∶1.12∶6.04,营养比例关系较好,但有机质含量较低,需采用后续浓缩步骤。研究表明,板式超滤膜滤出液基本符合纳滤、反渗透进水水质离子和pH值等的要求。

Experimental study on pretreatment of plate ultrafiltration membrane for biogas slurry

How to reduce the pollution of ultrafiltration membrane to the lowest level is an important issue. The ultrafiltration process is applied to the concentration of liquid organic fertilizer by membrane filtration of biogas slurry. Experimental study are determined to minimize the influence of concentration polarization. Pick up the biogas slurry in a farm and observe the flux change and removal of the plate-type ultrafiltration membrane under different pressures under different pressures. Under the pressure of 0.05~0.25 MPa, the initial flux of the plate type ultrafiltration membrane decreased rapidly.After 10~30 min, the flux decreased slowly and became stable, which was in good agreement with the empirical formula of membrane flux attenuation. The flux of the plate ultrafiltration membrane increased with the increase of pressure, but the growth rate gradually decreased. The membrane rejection rate has little to do with the pressure change. The removal rate of COD is relatively high, about 70%. The removal rate of NH₄⁺-N, K⁺ and other small molecular substances is relatively poor, only 22%~40%. The small molecular nutrients are well preserved. The nutrient index of the filtrate is 0.16% for organic matter, 0.217% for inorganic total nutrition, and 10:1.12:6.04 for N-P₂O₅-K₂O. The nutrient ratio is relatively good, but the organic matter content is relatively low, so subsequent concentration steps are needed.The experimental results show that the filtrate of plate ultrafiltration membrane basically meets the ions and pH value requirements of nanofiltration and reverse osmosis.