Enhancing Microalgae Cultivation In Anaerobic Digestion Piggery Effluent Through Fungal Decolorization

At present,there are three treatment modes of pig farm manure:returning to field,natural treatment and industrial treatment.Biogas project is an important way to solve the pollution control and resource utilization of aquaculture waste,but biogas slurry,a byproduct of biogas project,is a difficult problem to deal with at present.Biogas slurry is rich in a large amount of nutrients and is a potential resource for chlorella utilization.Previous studies have also verified that chroma and high ammonia nitrogen are the limiting factors for microalgae to treat biogas slurry.Fungi have the ability of adsorption and decolorization to treat wastewater.The technological route of using fungi to pretreat biogas slurry and then raise Chlorella can not only solve the problem of environmental pollution of biogas slurry,but also recycle chlorella biomass as high value-added products.This project mainly explore the screening suitable strains of biogas slurry pretreatment,explore various factors under the strain effect on the decolorizing efficiency of biogas slurry,research laboratory building small air lift reactor zoom in shake flask test running stability,and to explore the chlorella in biogas slurry after pretreatment of growth and nutrient change,the main work and the experimental results were as follows:（1）We carried out a series of sample collection and strain screening,separation and purification.Four strains were selected for re-screening through shaker test with decolorization ability as the screening index.Finally,the target strain Lichtheimia Ornata（Mucor）was obtained,named NU-27.NU-27 had an obvious decolorization effect on biogas slurry and nutrient components.After 4 days of decolorization in 10%biogas slurry medium,the decolorization rate reached 65.67%.（2）Optimization of pretreatment conditions of biogas slurry by fungus NU-27:The optimal decolorization conditions were 3 g·L^-1 glucose,10⁵spores/m L,30℃,140 rpm and initial p H 6.Under the optimal conditions,the decolorization rate was94.20%for 48 h.The removal rates of NH₄⁺-N,TN and COD were 64.82±0.76%,42.39±0.79%and 62.86±1.22%.（3）A small air-lift reactor was designed and built.The decolorization effect of fungi in the reactor was stable,and the settlement of the biogas slurry after treatment was good.Microscopic observation showed that NU-27 formed mycelium adsorption and degraded the decolorization substance in the biogas slurry to achieve the decolorization effect.（4）In the optimization of biogas slurry culture conditions after treatment,stable and efficient chlorella culture was achieved by adjusting the initial OD and p H,and the maximum OD value was up to 2.239.In the optimal culture conditions,the maximum removal rates of NH₄⁺N、TN、TP and COD were calculated to be 88%、58%、65%and 77%,respectively.The significant process optimization was achieved by optimizing the culture conditions.