Sludge reduction with Tubificidae and the impact on the performance of the wastewater treatment process

To reduce excess sludge, a Tubificidae reactor was combined with an integrated oxidation ditch with vertical circle （IODVC）, and a new integrated system was developed for wastewater treatment, A pilot-scale of this integrated system was tested to investigate the sludge reduction with Tubificidae and the impact on effluent quality and sludge production. The dominant worm was Branchnria Sowerbyi in the Tubificidae reactor after inoculation of Branchnria Sowerbyi and Limnodrilns sp., and the maximal volume density of wet Tubificidae in vessels of the Tubificidae reactor was 17600 g/m^3. Two operational modes, treating the excess sludge （first mode） and the returned sludge （second mode） of IODVC by the Tubificidae reactor, were used in this experiment. The results showed that the excess sludge reduction rate was 46.4% in the first mode, and the average sludge yield of the integrated system was 6.19× 10^-5 kg SS/kg COD in the second mode. Though the sludge returned to IODVC via the Tubificidae reactor, it had little impact on the effluent quality and the sludge characteristics of the IODVC. No new type of recalcitrant substance in the supernatant was discharged into the environment when the sludge was treated by Tubificidae. The experimental results also indicated that no significant changes occurred on the viscosity, specific resistance, and the floc size distribution of the sludge.

Evaluation of In-situ Sludge Reduction and Enhanced Nutrient Removal in an Integrated Repeatedly Coupling Aerobic and Anaerobic and Oxic-setting-anaerobic System

Aiming to achieve simultaneous good performances of in-situ sludge reduction and effluent quality,an integrated repeatedly coupling aerobic and anaerobic and oxic-setting-anaerobic system( r CAA + OSA) is developed to reduce sludge production and enhance nutrient removal. Considering the mechanism of in-situ sludge reduction in this r CAA +OSA system,the combined effect of energy uncoupling metabolism and sludge cryptic growth maybe attributed to the higher reduction of biomass. Results show that the maximal sludge reduction in this r CAA + OSA system is obtained when the hydraulic retention time( HRT) is controlled at6. 5 h,which an increase in 16. 67% reduction in excess sludge is achieved compared with OSA system( HRT of 6. 5 h). When compared the performances of effluent qualities,the enhanced nutrient removal efficiencies also can be observed in this r CAA + OSA system. Three-dimensional excitation emission matrix( 3D-EEM)fluorescence spectroscopy is applied to characterize the effluent organic matters( Ef OM) under different HRTs in the OSA and the r CAA+OSA systems. Analyses of 3D-EEM spectra show that more refractory humic-like and fulvic-like components are observed in the effluent of the OSA system. On the basis of these results,simultaneous enhanced in-situ sludge reduction and improved nutrient removal can be obtained in the r CAA +OSA systems.

Advanced sludge reduction and phosphorous removal process

An advanced sludge reduction process, i.e. sludge reduction and phosphorous removal process, was developed. The results show that excellent sludge reduction and biological phosphorous removal can be achieved perfectly in this system. When chemical oxygen demand ρ（COD） is 332 - 420 mg/L, concentration of ammonia p（NH3-N） is 30 - 40 mg/L and concentration of total phosphorous p（TP） is 6.0 -9.0 mg/L in influent, the system still ensures ρ（COD）〈23 mg/L, ρ（NH3-N）〈3.2 mg/L and ρ（TP）〈0. 72 mg/L in effluent. Besides, when the concentration of dissolved oxygen ρ（DO） is around 1.0 mg/L, sludge production is less than 0. 140 g with the consumption of 1 g COD, and the phosphorous removal exceeds 91 %. Also, 48.4% of total nitrogen is removed by simultaneous nitrification and denitrification.

Implementing Both Domestic Wastewater Reuse and Sludge Reduction by a Combination of Anaerobic Phase and Membrane bioreactor

The aim of the research was to obtain both an excellent effluent for reuse and a reduced sludge production simultaneously by a combination process of anaerobic phase and Membrane bioreactor （MBR） technology in treating domestic wastewater. During the experimental period of three months, excellent removals for COD, NH3-H, TN were obtained, and mean removals were 91.87%, 96.13%, and 69. 23%, respectively. Whereas, at first 20 days, the removal for TP was only about 15.87%. In the following days, about 30% of raw water was introduced into the anaerobic reactor to supply organics for denitrificatien and release of polyphosphate, then a significant improvement for TP removal was observed, and mean removal of TP increased to 76.35%. During the operational period, it was investigated that the permeate could meet the requirements of several water criteria for reuse except free chlorine, and a mean excess sludge yield coefficient of 0.137 g MLSS/g COD was obtained. Therefore, the predicted goals of permeate for reuse and excess sludge reduction could be both achieved after dosing a certain quantity of disinfectant into the permeate.

Sludge Drying and Incineration Method Applied to Sludge Reduction Research

This work takes sludge drying and incineration and pollutant discharge characteristics as the main line of research.With sludge dewatered by a certain sewage plant in southern Jiangsu using machinery and chemical conditioners selected as the research object,the influencing factors such as particle size,drying temperature and sludge reverse-mixing ratio in the sludge drying process were mainly explored,and the best working conditions of sludge drying were further analyzed.On this basis,in-depth research was carried out on the pollutants such as NO_(x),SO_(2),HCl,CO and other pollutants generated in the sludge incineration process by investigating the incineration temperature,sewage,the sludge moisture content and excess air coefficient.The results showed that the best conditions for sludge drying were as follows:particle size 3.5 mm,temperature 210℃and reverse-mixing ratio 25,and the cumulative drying time of the sludge 445.21 min.Through the research on the pollutant emission characteristics of sludge incineration,it was found that the incineration temperature and the moisture content of the sludge had a greater impact on the emission concentrations of NO_(x),SO_(2),HCl,and CO.Among them,the incineration temperature was the key factor that affected the generation of NO_(x),SO_(2),HCl,and CO.

Investigate of in situ sludge reduction in sequencing batch biofilm reactor:Performances,mechanisms and comparison of different carriers

Biofilm is an effective simultaneous denitrification and in situ sludge reduction system,and the characteristics of different biofilm carrier have important implications for biofilm growth and in situ sludge reduction.In this study,the performance and mechanism of in situ sludge reduction were compared between FSC-SBBR and SC-SBBR with constructed by composite floating spherical carriers(FSC)and multi-faceted polyethylene suspension carriers(SC),respectively.The variation of EPS concentration indicated that the biofilm formation of FSC was faster than SC.Compared with SCSBBR,the FSC-SBBR yielded 0.16 g MLSS/g COD,almost 27.27%less sludge.The average removal rates of COD and NH_(4)^(+)-N were 93.39% and 96.66%,respectively,which were 5.21% and 1.43% higher than the average removal rate of SC-SBBR.Investigation of the mechanisms of sludge reduction revealed that,energy uncoupling metabolism and sludge decay were the main factors for sludge reduction inducing 43.13%and 49.65%less sludge,respectively,in FSC-SBBR.EEM fluorescence spectroscopy and SUVA analysis showed that the hydrolytic capacity of biofilm attached in FSC was stronger than those of SC,and the hydrolysis of EPS released more DOM contributed to lysis-cryptic growth metabolism.In additional,Bacteroidetes and Mizugakiibacter associated with sludge reduction were the dominant phylum and genus in FCS-SBBR.Thus,the effect of simultaneous in situ sludge reduction and pollutant removal in FSC-SBBR was better.

Co-application of energy uncoupling and ultrafiltration in sludge treatment:Evaluations of sludge reduction,supernatant recovery and membrane fouling control

Energy uncoupling is often used for sludge reduction because it is easy to operate and does not require a significant amount of extra equipments(i.e.no additional tank required).However,over time the supernatant extracted using this method can deteriorate,ultimately requiring further treatment.The purpose of this study was to determine the effect of using a low-pressure ultrafiltration membrane process for sludge water recovery after the sludge had undergone an energy uncoupling treatment(using 3,3’,4’,5-tetrachlorosalicylanilide(TCS)).Energy uncoupling was found to break apart sludge floe by reducing extracellular polymeric substances(EPS)and adenosine triphosphate(ATP)content.Analysis of supernatant indicated that when energy uncoupling and membrane filtration were coapplied and the TCS dosage was below 30 mg/L,there was no significant deterioration in organic component removal.However,ammonia and phosphate concentrations were found to increase as the concentration of TCS added increased.Additionally,due to low sludge concentrations and EPS contents,addition of 30-60 mg/L TCS during sludge reduction increased the permeate flux(two times higher than the control)and decreased the hydraulic reversible and cake layer resistances.In contrast,high dosage of TCS aggravated membrane fouling by forming compact fouling layers.In general,this study found that the co-application of energy uncoupling and membrane filtration processes represents an effective alternative method for simultaneous sludge reduction and sludge supernatant recovery.

Metabolic uncoupler,3,3’,4’,5-tetrachlorosalicylanilide addition for sludge reduction and fouling control in a gravity-driven membrane bioreactor

The gravity-driven membrane bioreactor(MBR)system is promising for decentralized sewage treatment because of its low energy consumption and maintenance requirements.However,the growing sludge not only increases membrane fouling,but also augments operational complexities(sludge discharge).We added the metabolic uncoupler 3,3’,4f,5-tetrachlorosalicylanilide(TC$)to the system to deal with the mentioned issues.Based on the results,TCS addition effectively decreased sludge ATP and sludge yield(reduced by 50%).Extracellular polymeric substances(EPS;proteins and polysaccharides)decreased with the addition of TCS and were transformed into dissolved soluble microbial products(SMPs)in the bulk solution,leading to the break of sludge floes into small fragments.Permeability was increased by more than two times,reaching 60-70 L/m2/h bar when 10-30 mg/L TCS were added,because of the reduced suspended sludge and the formation of a thin cake layer with low EPS levels.Resistance analyses confirmed that appropriate dosages of TCS primarily decreased the cake layer and hydraulically reversible resistances.Permeability decreased at high dosage(50 mg/L)due to the release of excess sludge fragments and SMP into the supernatant,with a thin but more compact fouling layer with low bioactivity developing on the membrane surface,causing higher cake layer and pore blocking resistances.Our study provides a fundamental understanding of how a metabolic uncoupler affects the sludge and bio-fouling layers at different dosages,with practical relevance for in situ sludge reduction and membrane fouling alleviation in MBR systems.

Carbon source recovery from waste sludge reduces greenhouse gas emissions in a pilot-scale industrial wastewater treatment plant

Carbon cycle regulation and greenhouse gas(GHG)emission abatement within wastewater treatment plants(WWTPs)can theoretically improve sustainability.Currently,however,large amounts of external carbon sources used for deep nitrogen removal and waste sludge disposal aggravate the carbon footprint of most WWTPs.In this pilot-scale study,considerable carbon was preliminarily recovered from primary sludge(PS)through short-term(five days)acidogenic fermentation and subsequently utilized on-site for denitrification in a wool processing industrialWWTP.The recovered sludge-derived carbon sources were excellent electron donors that could be used as additional carbon supplements for commercial glucose to enhance denitrification.Additionally,improvements in carbon and nitrogen flow further contributed to GHG emission abatement.Overall,a 9.1%reduction in sludge volatile solids was achieved from carbon recovery,which offset 57.4%of external carbon sources,and the indirect GHG emissions of the target industrial WWTP were reduced by 8.05%.This study demonstrates that optimizing the allocation of carbon mass flow within a WWTP has numerous benefits.

Performance of biological phosphorus removal and characteristics of microbial community in the oxic-settling-anaerobic process by FISH analysis

Performance of biological phosphorus removal in the oxic-settling-anaerobic(OSA) process was investigated. Cell staining and fluorescent in situ hybridization(FISH) were used to analyze characteristics and microbial community of sludge. Experimental results showed that phosphorus removal efficiency was near 60% and the amount of biological phosphorus accumulation in aerobic sludge of the OSA system was up to 26.9 mg/g. Biological phosphorus removal efficiency was partially inhibited by carbon sources in the continuous OSA system. Contrasted to the OSA system,biological phosphorus removal efficiency was enhanced by 14% and the average total phosphorus(TP) contents of aerobic sludge were increased by 0.36 mg/g when sufficient carbon sources were supplied in batch experiments. Staining methods indicated that about 35% of microorganisms had typical characteristics of phosphorus accumulating organisms(PAOs) . FISH analysis demonstrated that PAOMIX-binding bacteria were predominant microbial communities in the OSA system,which accounted for around 28% of total bacteria.