Influence of external circulation on sludge characteristics during start-up of internal circulation reactor

The start-up of external circulationadded internal circulation(IC) reactor was finished in 26 d, 32 d fewer than that of IC reactor. To evaluate the influence of the added external circulation on the development of granular sludge, the characteristics of the granular sludge taken from the two tested laboratory-scale reactors during start-up were studied. The results show that the added external circulation can enhance biomass granulation, accelerate granule development and improve sludge characteristics. At the end of start-up, the granular size of sludge in external circulation-added IC reactor greatly increases with a size distribution much better than that of sludge in IC reactor. The granular sludge originated from external circulationadded IC reactor contains more extracellular polymers and has a greater settling velocity than that from IC reactor. Methanogenic activity of the granular sludge from the external circulationadded IC reactor started 26 d ago reaches 358.23mL·g -1 ·d -1 , 1.66 and 1.20 times as great as that of the sludge from the IC reactor started 26 d and 58 d ago respectively.

Coagulation efficiency and flocs characteristics of recycling sludge during treatment of low temperature and micro-polluted water

Drinking water treatment sludge,characterized as accumulated suspended solids and organic and inorganic matter,is produced in large quantities during the coagulation process.The proper disposal,regeneration or reuse of sludge is,therefore,a significant environmental issue.Reused sludge at low temperatures is an alternative method to enhance traditional coagulation efficiency.In the present study,the recycling mass of mixed sludge and properties of raw water （such as pH and turbidity） were systematically investigated to optimize coagulation efficiency.We determined that the appropriate dosage of mixed sludge was 60 mL/L,effective initial turbidity ranges were below 45.0 NTU,and optimal pH for DOMs and turbidity removal was 6.5-7.0 and 8.0,respectively.Furthermore,by comparing the flocs characteristics with and without recycling sludge,we found that floc structures with sludge were more irregular with average size growth to 64.7 μm from 48.1 μm.Recycling sludge was a feasible and successful method for enhancing pollutants removal,and the more irregular flocs structure after recycling might be caused by breakage of reused flocs and incorporation of powdered activated carbon into larger flocs structure.Applied during the coagulation process,recycling sludge could be significant for the treatment of low temperature and micro-polluted source water.

Performance of bioferric-submerged membrane bioreactor for dyeing wastewater treatment

Adding iron salt or iron hydroxide to sludge-mixed liquor in an aeration tank of a conventional activated sludge processes(bioferric process)can simultaneously improve the sludge’s filterability and enhance the system’s treatment capacity.In view of this,Fe(OH)3 was added to a submerged membrane bioreactor(SMBR)to enhance the removal efficiency and to mitigate membrane fouling.Bio-ferric process and SMBR were combined to create a novel process called Bioferric-SMBR.A side-by-side comparison study of Bioferric-SMBR and common SMBR dealing with dyeing wastewater was carried out.Bioferric-SMBR showed potential superiority,which could enhance removal efficien-cy,reduce membrane fouling and improve sludge character-istic.When volumetric loading rate was 25% higher than that of common SMBR,the removal efficiencies of Bioferric-SMBR on COD,dye,and NH_(4)^(+)-N were 1.0%,9.5%,and 5.2%higher than that of common SMBR,respectively.The trans-membrane pressure of Bioferric-SMBR was only 36%of that in common SMBR while its membrane flux was 25% higher than that of common SMBR.The stable running period in Bioferric-SMBR was 2.5 times of that in common SMBR when there was no surplus sludge discharged.The mixed liquor suspended solids concentration of Bioferric-SMBR was higher than that of common SMBR with more diversified kinds of microorganisms such as protozoans and metazoans.The mean particle diameter and specific oxygen uptake rate of Bioferric-SMBR were 3.10 and 1.23 times the common SMBR,respectively.