Preparation And Application Of Coupled Functional Algal Fertilizer For Purification Of Chicken Farm Flushing Wastewater By Scenedesmus Obliquus

The treatment of livestock and poultry wastewater has been one of the most bothersome issues to be solved because it contains a high amount of heavy metals,nitrogen,phosphorus,and antibiotics,which has become one of the important factors of ecological environment pollution.The newly developed application of microalgae to purify livestock and poultry wastewater is a high efficiency,low cost,sustainable and circular value-added environmental treatment system.It can not only effectively remove phosphorus and nitrogen and purify wastewater,but also obtain a large amount of microalgae biomass for the development of bio-chemical and bio-fuel and other high value-added products.Integrating microalgae to treat livestock and poultry wastewater to produce functional fertilizers,feedstuffs and biological stimulants and other agricultural green products is giving rise to a green high-value industrial system with integration of workers and farmers.In-depth analysis of the biological and technological issues involved in this system will provide theoretical and technical support for the development of this emerging industry.In this paper,focusing on the core problem of resource utilization of chicken farm waste water,a technical system of fenton method for pretreatment of chicken farm waste water coupled microalgae culture was established with the slant grid algae as the target algae species,so as to effectively purify waste water and produce high-quality microalgae biomass.The effects of microalgae bio-fertilizer on the growth,yield and quality of rapeseed were studied in greenhouse by using microalgae biomass to prepare bio-fertilizer.The main research results are as follows:1.According to the test of the washing circle wastewater of the chicken farm,the main components of the original CW background include: total nitrogen 2182 mg·L^-1,ammonia nitrogen 1602 mg· L^-1,COD 5647 mg· L^-1 and total phosphorus content 151 mg· L^-1.The waste water was directly inoculated with algal cells(2.0/OD₆₅₀),and the algal cells could not grow normally.Artificial simulated wastewater background composition test found that high concentration of ammonia nitrogen is the main factor to inhibit the growth of algal cells,algal cells tolerate ammonia concentrations was 350 mg·L^-1。2.Fenton oxidation method was used to pretreat chicken farm wastewater to reduce the concentration of ammonia nitrogen in the original solution and remove the restriction on the growth of microalgae.The optimal Fenton reaction system was constructed: Fe2+ 20 g·L^-1,H₂O₂ 50 mL·L^-1,p H3,temperature 25℃,reaction time 60 min.The Fenton reaction system was used to pretreat the chicken farm wastewater,which significantly reduced the ammonia concentration of the original solution to < 350 mg·L^-1,and the removal rate of other components in the original solution reached about 50%.The pretreatment of chicken farm wastewater also seriously inhibited the growth of algae cells.Further tests proved that the higher H₂O₂ residue in wastewater after Fenton pretreatment could inhibit the normal growth of algal cells.3.In order to eliminate the inhibitory effect of high residual H₂O₂ on the growth of algal cells after Fenton treatment of chicken farm wastewater,Fenton system with different concentration gradient of H₂O₂ was used to treat chicken farm wastewater and mix it with clean water in 1:1,and the residual H₂O₂ was reduced by dilution,so that it could be used to culture microalgae.The system test showed that after the treatment of chicken farm wastewater by Fenton method with clear water and 1:1 dilution,the algal cells could grow when the concentration of H₂O₂ was 50 mL· L^-1,while other concentration could not grow,the main components in the waste water solution were significantly reduced,the total nitrogen was 600 mg·L^-1,the total phosphorus was 45 mg· L^-1,the COD was 1800 mg· L^-1,and the residual ammonia nitrogen was 360 mg· L^-1.After Fenton treating chicken farm wastewater with this diluted and continuously culturing Scenedesmus for one week,the microalgal biomass yield reached 4.0 / OD₆₅₀.The removal rate of total phosphorus in the original wastewater was 91%,while that of total nitrogen,COD and ammonia nitrogen was 99%.Compared with the treatment of chicken farm wastewater by physical and other biological methods,the system of "Fenton pretreatment-1:1 dilution-algal culture" established in this paper not only significantly reduces the water consumption,but also obtains a large amount of microalgae biomass.4.Liquid microalgae biofertilizer(3/OD₆₅₀)was obtained by using the system of "Fenton pretreatment-1:1 dilution-algal culture" to treat chicken farm wastewater for 1 week.Blank group,single alga group,single fertilizer group,fer-alga 10 mL,fer-alga 20 mL,fer-alga 30 mL.The results showed that 10 mL,20 mL and 30 mL of fer-algae had the best growth promoting effects.Compared with the blank group,the single algae group and the single fertilizer group,the dry weight,cellulose,root activity,chlorophyll a and chlorophyll b of the Lactuca sativa in the fer-algal fertilizer treatment group were significantly increased,and the 20 mL fer-alga group was 1.7 times as much as the blank group in the root activity index,and the former was 1.5 times as much as the latter in the chlorophyll and leaf width indexes.In terms of dry weight and cellulose index,the fer-algal 30 mL group was 2.42 and 2.38 times that of the blank group,respectively.The nitrogen content in the leaves of rapeseed leaves treated by the fat-alga 30 mL group increased by 100% and 65%,respectively,compared with the blank group and the single fertilizer group.The contents of N,P and K in the soil in the blank group and the single algae group were lower than those in the other four groups and the difference was significant.The difference between the four groups except the blank group and the monoalgae group was not significant.In a word,this paper successfully constructed an optimized process system of Fenton method for pretreatment of chicken farm wastewater coupled microalgae culture,and the obtained microalgae biomass as a high-quality biological fertilizer can be used in agricultural production to replace conventional fertilizers or with conventional fertilizers,so as to reduce the amount of fertilizer used.These findings lay a foundation for the establishment of a new process system for large-scale microalgae purification of livestock and poultry wastewater and the production of high quality bio-fertilizer and other environmentally friendly agricultural products as well as its application in green and efficient agriculture.