The Initial Study Of Improving The Productivity Of VFA In The Hydrolysis And Acidification Of Aquaculture Solids

A high level concentration of nitrate nitrogen in the Recirculating AquacultureSystem will influence the growth of the aquatic significant, or lead them to death indeed.Recently, the methods of nitrate nitrogen management at home and abroad are physicalmanagement, chemical management and biological management. Comparing with othertechnologies, biological heterotrophic denitrifying method is the ordinary technology indealing with the nitrate nitrogen. The VFA (Volatile fatty acids) which the aquaculturesolids hydrolysis and acidification are used as the carbon source for heterotrophicdenitrifying reaction that could be highly used by the denitrifying microorganism. It canlargely reduce solid wastes, purify water and multipurpose use the waste. Therefore, theresearch about the aquaculture solids in the hydrolysis and acidification is benefit for usto develop the source of the carbon in denitrification more.Improving the productivity of VFA of the aquaculture solids in the hydrolysis andacidification could provide enough source of carbon in nitration reaction effectively. Inorder to increase the concentration of VFA of the aquaculture solids in the hydrolysisand acidification, this paper mainly studies three key factors which influence theproductivity of VFA: residence time, temperature and the pH, so that the condition ofproducing VFA of the aquaculture solids in the hydrolysis and acidification could beoptimized.This paper studies the effect of the aquaculture solids producing VFA in anaerobicfermentation hydrolysis, the proportional relationship between the SCOD and theTCOD, the proportional relationship between the SCOD and the concentration of VFA,and the change of the pH, ammonia nitrogen and ORP when the residence time is18days. The result shows that: residence time has quite great influence on the hydrolysisfermentation of the solids. In this18days, the effect of producing VFA by hydrolysisfermentation is the best in the sixth day, the concentration is2609.18mg/L, the maximum of all. From the seventh day, it begins to decrease gradually, and in the18thday down to1899.72mg/L; the ratio between SCOD and TCOD is rising up gradually;the productivity of VFA just6%in the content of SCOD; the pH accords with thegrowing range of the bacterium of hydrolyze and acidification; the total concentration ofammonia nitrogen is quite low in the whole process,＜0.07mg/L.This paper studies the effect of the aquaculture solids producing VFA in anaerobicfermentation hydrolysis, the proportional relationship between the SCOD and theTCOD, the proportional relationship between the SCOD and the concentration of VFA,and the change of the PH, ammonia nitrogen and ORP in5temperatures (25℃、30℃、35℃、40℃、45℃). The result shows that: the temperature factor has quite greatinfluence on the Hydrolysis fermentation of the solids. When the temperature is below35℃, the productivity of VFA by hydrolysis fermentation increases as the temperaturerises up, and the maximum is2609.18mg/L in35℃. When the temperature reaches45℃, the concentration of VFA is989.69mg/L; the ratio between SCOD and TCODincreases as the temperature rises up; the productivity of VFA just5.9%in the contentof SCOD; the value of the pH turns up to decline which accords with the growing rangeof the bacterium of hydrolyze and acidification in different temperatures; the totalconcentration of ammonia nitrogen is quite low in the whole process,＜0.10mg/L.This paper systematically studies the effect of the aquaculture solids producingVFA in anaerobic fermentation hydrolysis, the proportional relationship between theSCOD and the TCOD, the proportional relationship between the SCOD and theconcentration of VFA, and the change of the pH, ammonia nitrogen and ORP when thevalue of the pH is5,6,7,8,9. The result shows that: the pH factor has quite greatinfluence on the Hydrolysis fermentation of the solids. When the value of the pH is7,the effect of producing VFA is better than others’, the concentration is5397.03mg/L.The concentration of VFA producing by the system if PH has been adjusted is higherthan which has not. The concentration of VFA when the pH is adjusted to7is twice thanwhich has not; the ratios between SCOD and TCOD in different pH are different, it ishigher than other ratios when the pH is7, and the ratio when the pH has been adjusted isalso higher than those have not; the productivity of VFA just5.89%in the content ofSCOD; in this experiment, the change of pH tend to the one which need to be adjustedin the system which has been control in5pH, and the pH which have not been adjusteddecrease from7.2to4.0and then tend to be stable in the six day experiment; the total concentration of ammonia nitrogen is quite low in the whole process,＜0.155mg/L.Above studying, provides the basis to optimize the aquaculture solids hydrolysisproduce VFA in the hydrolysis fermentation, and it makes sense for exploitingdenitrification carbon source has a certain significance in the future.