Research On The Short Chain Fatty Acids Production From The Hydrolysis And Acidification Of Waste Activated Sludge

Along with more and more sewage plant and growing sewage treatment rate,waste activated sludge disposal problem have become increasingly prominent. Moreand more attention had been paid to the organic matters in the waste activated sludge.Many studies have explored how to reuse the organic matters in waste activated sludgemore efficiency and tried best to create more profit. The ultimate goal of this research isto produce fermentation substrate, which is suitable for PHAs production with high C/N value of pilot scale. And also this study can also be considered as optimal operationstudy on short chain volatile fatty acids production from waste activated sludge.Firstly, this study focused on the factors which influence short-chain volatile fattyacids production from waste activated sludge, including temperature, sludgeconcentration and sludge types in bench scale. The results showed that the sludge can behydrolysised and acidificated by itself. At room temperature, sludge is hard to behydrolysised and acidificated. Elevating temperature (30-50degrees Celsius) isbeneficial to improve the sludge reaction rate, and can increase the yield of VFAs. Butwhen the temperature rises to a certain extent (60degrees Celsius), the effect is notobvious. VFAs distributions are affected by source of sludge and sludge concentrations.Source of sludge determines which VFAs have the more yield than others. The moreconcentrations of sludge being used, the more types and yield of VFAs we got. In all,the optimal operation conditions for this study are: the temperature is50degrees Celsius;sludge concentration is30mg/L.Then this study researched on sludge hydrolysis and acidification process at hightemperature (50degrees C) in the lab scale. It is concluded that waste activated sludgecould reach stable operation state at50degrees C with the yield of VFAs remaining250-280(mg-COD/g-VSS). Hydrolysis and acidification is in good condition. Aceticacid, butyric acid and isovaleric acid are the most acids accounting for70%of all theacids yield. But their specific sequence is determined by pH during the process. In acertain range, when pH got a slight elevation, we could got more isovaleric acid andbutyric acid accumulation. Also, accompanied by sludge hydrolysis and acidification,the nitrogen element are released and ammonia nitrogen source accounted for more than 70%.As clinoptilolite has adsorption exchange ability on ammonia, we can useclinoptilolite to enhance C/N value of hydrolysis and acidification liquid of wasteactivated sludge. Clinoptilolite could raise C/N value of hydrolysis and acidificationliquid of waste activated sludge from2.4up to more10. And clinoptilolite inregeneration liquid (NaOH+NaCl (3/7)) got the regeneration rate of93%, regeneratedliquid ammonia nitrogen stripping ratio being83%.Finally, the effect of sludge retention time (SRT) on waste activated sludgehydrolysis and acidification have been investigated. When SRT increase slightly, it wasin favor for VFAs accumulation. But SRT increases to a certain degree, followed bymethane-producing stage. In brief, SRT=2d.Under this condition, the yield of VFAsremains140-160(mg-COD/g-VSS), VFA/COD value being85%.