Micro-aerobic Hydrolysis Acidification Process Of Sludge

As urbanization and industrialization developed rapidly, the production of sludge in sewage plant would be more and more. A large a number of sludge can not be treated with correct way, the sludge is placed discretionally, which is not only a serious burden of sewage plant, but also a new environmental pollution factors. As a result, lots of untreated sludge make environmental pollution in vain and bring in serious safety threaten for local environment.As a new kind of treatment technology, sludge hydrolysis and acidification process can not only treat and disposal sludge effectively, but also the fermentation products can be used as the effective carbon source for the biological nitrogen and phosphorus removal process. So sludge hydrolysis and acidification process make sludge reduction and resources come true at the same time.The experimental sludge selected from Zhengyang sewage treatment plant, Jinzhong city, Shanxi Province, under micro-aerobic conditions (DO<1.0mg/L), the effect of aeration rate, HRT, pH on VFAs, SCOD, solubility protein, solubility sugar, VS removal rate and the change rules of ammonia nitrogen and orthophosphate were studied. The conclusion as follows:(1) Under the condition of 21±1℃,pH 6.5～7.0, HRT6d, the result show that when the aeration rate were 0,0.2,0.4,0.6 L/min, the results revealed the highest value of SCOD, VFAs, solubility protein, solubility sugar and the removal rate of VS appeared at aeration rate of 0.4L/min, respectively 1717mg/L,1278 mg/L,40.6mg/L,47.2mg/L,49.8%, compared with 0 aeration rate, that increased by 78.8%,126%,79.6%,51.2%,19.5% respectively, the top value of sludge acid production was 0.128gCOD/gVS.Under micro-aerobic conditions, with the increase of aeration amount, both ammonia and orthophosphate concentration decreased, the lowest value appeared at aeration rate of 0.6 L/min, respectively 174 mg/L and 37 mg/L. In addition, sludge dewatering performance under different aeration were studied, the results showed the sludge specific resistance minimum of 6.87×1011m/Kg appeared at aeration of 0.4L/min, the dehydration performance was the best.(2) Under the condition of 21±1℃, aeration rate 0.4L/min, pH value 6.5～ 7.0, effect of HRT on the micro-aerobic hydrolysis and acidification was studied. When HRT were 3d,4d,6d, the results showed the hydrolysis efficiency and the acid yield of sludge would be higher with the longer HRT. With the extending of the HRT, SCOD, VFAs, solubility protein, solubility sugar and the removal rate of VS in fermentation liquid showed a rising trend, the top value all appeared at HRT6d,respectively 1540mg/L,942mg/L,23.5mg/L,42.5mg/L,47%. Compared with HRT3d, that increased by 43.9%,43.9%,64.9%,36%,42.4% respectively. The top value of sludge acid production was 0.094g COD/g VS. In addition, with the extending of the HRT, both ammonia nitrogen and orthophosphate concentration in reactor showed an increasing trend, the maximum value appeared at HRT6d, were 271 mg/L and 43.25 mg/L, compared with HRT=3d, that increased by 34.3%、34.8%.(3) Under the condition of 21±1℃, aeration rate 0.4L/min, HRT=6d, effect of pH value on micro-aerobic hydrolysis and fermentation was studied. When pH value were 6.0,6.5,7.0,7.5, SCOD, VFAs, solubility protein, solubility sugar and the removal rate of VS in fermentation liquid showed the same change rules,that was increased first and then decreased, the maximal value all appeared at pH7.0, respectively 2640mg/L,1540mg/L,53mg/L,54.6mg/L,43%. The top value of sludge acid production was 0.154gCOD/gVS.With the increasing of pH value, the stronger basic condition of the reactor made dissolved concentration of ammonia nitrogen and orthophosphate decreased, the lowest value appeared at pH7.5, respectively 273mg/L and 64mg/L.(4) Under the condition of 21±1℃,aeration rate 0.4L/min,HRT 6d,pH 7.0,the value of SCOD,VFAs,solubility protein, solubility sugar and the removal rate of VS were maximum,except of the concentration of ammonia nitrogen and orthophosphate were a little higher under HRT6d.But considering all of aspects,sludge acid-production was the most important factor in sludge micro-aerobic hydrolysis and acidification system,so when temperature was 21±1℃, aeration rate 0.4L/min, HRT 6d, pH 7.0 was the best experimental condition.(5) Acid producing bacteria under different aeration conditions was counted and separated and identified. The results showed that:the quantity of acid producing bacteria was the most at aeration rate of 0.4 L/min, which consistent with acid production maximum at 0.4 L/min. According to the morphology and physiological and biochemical reaction characteristics of acid producing bacteria, acid bacteria in reactor could be classified flavobacterium, aeromonas, arthrobacter, microbacterium, shigella, salmonella, brevibacterium.