| The rapid development of swine industy genereated large amounts of swinemanure wastewater. The traditional method for swine manure pretreatment is toproduce biogas through anaerobic digestion. However, the residual biogas slurry stillcontained nitrogen, phosphorus and organic compounds with high concentration. Thisstudy aims to treat swine farm biogas slurry by Chlorella and fungi-microalgaesymbiotic system formed by Chlorella and Pleurotus ostreatus for effective biogasslurry nutrient removal and low cost algal biomass production. In addition, the systemprovides a feasible way for simultaneous swine farm biogas slurry treatment andutilization. The main study results were as follows:1. The microalgae which adapted well in swine farm biogas slurry were isolatedfrom the biogas slurry. The strain was subsequently identified as Chlorella sp.through morphological observation and was used for swine farm biogas slurrytreatment. The growth rate and nutrients removal efficiency were investigated. Theresults showed that Chlorella had a purification effect for biogas slurry and it wasfound that the key factor affecting the growth of Chlorella in slurry was highconcentration of ammonia.2. Sodium nitrate and dipotassium hydrogen phosphate were used as nitrogenand phosphorus sources for Chlorella. The growth rate of Chlorella increased withthe increase of nitrogen and phosphorus in a certain concentration. However, whenthe concentration of N and P continue to increase, the growth of Chlorella would beinhibited. Based on above results, the most suitable concentration of N and P were100mg/L and10mg/L, respectively. High concentration of ammonia was animportant factor in inhibiting the growth of Chlorella, however, low concentration ofammonia could promote the growth of Chlorella. The most suitable concentration ofammonia was10mg/L, when the concentration of ammonia exceeded40mg/L, thegrowth of Chlorella would be inhibited. 3. The optimal algae growth conditions for slurry dilution, the initial inoculum,and ventilation volume were20%, OD680=0.3and1.5L/min, respectively. Thegrowth of Chlorella cultivated in20%diluted slurry was superior to that in BG11medium. The biomass of Chlorella in20%diluted slurry increased by14.63%compared to that in BG11medium, and the lipid increased by52.38%, but crudeprotein with a decrease of20%. Chlorophyll in BG11medium was2times higherthan that in20%diluted slurry. The Chlorella grown in different medium bothcontained8essential amino acids for human, and with high contents of total essentialamino acids (16.97%and17.26%). The essential amino acid index (EAAI) forChlorella in20%diluted slurry was87.49, which is superior to that in BG11medium(76.54), suggesting that nutritional value of protein was higher for Chlorella in20%diluted slurry.The results showed that20%diluted slurry can replace BG11mediumfor Chlorella growth in a cost-effective way.4. The conditions for fungi-microalgae pellets formation were determined by pH,carbon and nitrogen sources. When BG11medium was supplemented with2%maltose,0.5%yeast extracts and the initial pH maintained at5.0, Chlorella andPleurotus ostreatus co-culture could form mycelial pellets under2000luxillumination at25±2°C and agitated at160rpm in an orbital shaker. Nutrient removalefficiency for fungi-microalgae system was higher than free Chlorella. Afterpurification, the fungi-microalgae complex was easy to be separated from the slurryand can accumulate more biomass. The fungi-microalgae complex had a high contentof protein and a full range of amino acids. The total essential amino acids were higherthan general plant protein. The amino acid composition was relatively balanced inaddition to the relatively low methionine and cysteine. The EAAI was68.77, so itcould be used as a good nutritional additives. When the fungi-microalgae complexwas add to the feed with high content of methionine and cystine, the feed with the... |
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