鸟粪石结晶-絮凝同步处理沼液实验研究

Study on Synchronized Struvite Crystallization and Flocculation Treating Biogas Slurry

针对鸟粪石结晶法回收沼液中氨氮和磷酸盐时生成的晶体细小、不易与水分离等问题,采用鸟粪石结晶法和絮凝法相结合的工艺处理沼液,同步富集回收沼液中氮、磷及各种有机质。研究了pH值、反应物摩尔比、搅拌速度、反应时间等因素对沼液中氨氮,总磷,COD去除效果的影响,考察了絮凝剂的优化反应条件,并对富集物的成分做了较全面分析。结果表明,pH值9.5,n(Mg2+)∶n(NH+4)∶n(PO3-4)=1.2∶1.0∶l.0,改性壳聚糖絮凝剂的投加量为500 mg·L-1,助凝剂粉煤灰的加入量为80 mg·L-1,搅拌速率为150 r·min-1,反应时间为20 min时,氨氮,总磷,COD的总去除率为81.2%,75.8%,62.6%,富集产物含有丰富的营养物质,可作为生物缓释肥。

When the struvite crystallization process was used to recycle Ammonia-nitrogen and phosphorus from biogas slurry, one of the problems was the very fine size of the resultant crystals, which were difficult to separate from the solution. This paper studied the synchronized struvite crystallization and flocculation to improve the treating of bingas slun＇y. Various factors, including pH value, molar ratio of reactants, stirring speed, and reaction time, were determined to analyze the effectiveness of this method on recovering ammonia-nitrogen, phosphorus, and organic compounds from biogas slurry. The optimal reaction conditions of flocculants were investigated, and the composition of the precipitate was analyzed comprehensively. The results showed that, at pH 9.5, and the ratio of n （ Mg2 ＋ ） ： n （ NH4^＋ ） ： n （ PO4^3- - ） was 1.2 ： 1.0 ： 1.0, with 500 mg· L^-1 of modified chitosan as flocculant and 80mg· L^-1 of fly ash as coagulant aid, a stlrrlng rate of 150mg· L^-1, and a reaction time of 20 min, the recovery rates of ammonia-nitrogen, total phosphorus, and COD were 81.2%, 75. 8%, and 62. 6%, respectlvely. The precipitate was rich in nutrients and could be used to produce a slow-release biological fertilizer.