Effect Of THPS On Sludge Reduction Characters And Process Operation Of Intermittent IFAS Process

In recent years,China’s annual production of sludge is increasing.High posttreatment costs of sludge makes people seek for practical technologies to reduce sludge production when treating sewage effectively.Among the already developed sludge reduction technologies,the method of adding chemical uncouplers has attracted the attention of scholars because of its effective sludge reduction efficiency and good operability.However,examinations followed indicates that the uncouplers studied and applied widely are all toxic and will bring about secondary pollution and other issues.It limits the practical applications of chemical uncouplers.In this paper,a new environmentfriendly uncoupler THPS and an intermittent IFAS process(integrated fixed-film activated sludge)are studied to develope a possible technology which can reduce sludge production effectively when treating sewage and brings about no secondary pollution.In this paper,the intermittent IFAS reactors were first started and the operating conditions were optimized.The results show that the optimal dissolved oxygen concentration DO of the fixed filler and flowing filler intermittent IFAS reactor is 4.5mg/L and 3mg/L,respectively.And the optimal C/N ratio in the influent is 6:1,considering the point of giving full play to the high efficiency of denitrification.The removal rate of COD,NH3-N and TN in flowing filler intermittent IFAS reactors are 90%,95% and 80%,respectively,which is better than in the fixed filler intermittent IFAS reactors.The environment-friendly performance of THPS was evaluated by a series of toxicological experiments and biodegradability experiments.With 2,4,6-TCP and 2,4-DNP which have been already studied and applied widely as contrast,the results showed that THPS had little inhibitory effect on microbes and had excellent biodegradability.Thus,it is indeed an environment-friendly uncoupler.Five flowing filler intermittent IFAS reactors were run continuously with the dissolved oxygen concentration was 3mg/L and the C/N ratio in the influent was 6:1.The effects of THPS in different influent concentrations on the intermittent IFAS process were studied,including sludge reduction effect,sewage treatment performance and sludge properties.The results showed that the effect of sludge reduction was obvious with THPS and the effect of sludge reduction was increased with the increase of dosing concentration.In the case of sewage treatment,when the THPS concentration in the influent was higher than 5mg/L,the reactors had bad sewage treatment performance.In the prophase of dosing THPS,the sewage treatment system collapsed.Especially the removal rate of total nitrogen and ammonia nitrogen dropped to below 40%.When the THPS concentration was less than 3mg/L,it will not significantly affect the sewage treatment effect.Considering the sewage treatment performance and sludge reduction together,the optimal concentration of THPS in the influent is 3mg/L.When the dosing concentration of THPS was 3mg/L,the rate of sludge reduction was 39.1%,and the average removal rates of COD,NH3-N,TN and TP was 83.1%,86.4%,69.8% and 58.9%,respectively.Thus,it is possible for practical engineering application when dosing concentration of THPS in the influent is 3mg/L.After 60 days’ continuous operation of the reactor,some sludge properties like the yield and variety of EPS,sludge settling and dewatering performance and elemental composition were studied.The results showed that when the dosing concentration of THPS in the influent was 3mg/L,the yield of EPS was not changed obvious compared with the control group,and the settling performance and heat value of sludge did not change obviously either.In contrast,the dewatering performance was improved to some extent.In general,the performance in various aspects of sludge was not affected obviously,when the dosing concentration of THPS was 3mg/L.