The Effects Of The Microwave Conditioning Combined With CPAM On The Structure And Dewaterability Of Sludge

Urban sewage treatment plant produces large amount and component of waste sludge. Therefore the enhancement of dewaterability becomes an important topic. The addition of polyelectrolyte to the sludge, which is presently the most common sludge conditioning method, increases costs and may cause secondary environmental pollution.In this paper, fractal theory is utilized to study sludge fractal structure characteristics under sludge conditioning. Differences of sludge structure parameters——specific resistance to filtration ?SRF?, water content of vacuum filtration, particle size ?do.s?, fractal dimension ?Df?, floc strength ?FS?, flocculation ability ?FA? and relative hydrophobicity ?RH? were analyzed after microwave conditioning and microwave combined with cationic polyacrylamide ?CPAM?. The effects of structure parameters on sludge dewatering characteristics were discussed for the sludge conditioning mechanism. The experiment result is as follows:Appropriate microwave radiation could obviously improve the dewateringability and sludge structure. Under the same microwave intensity, the SRF and water content of vacuum filtration were both dropped firstly and then increased with the radiation time. Results showed that D₂, D₃ and FS were also increased firstly and then decreased with the radiation time, but RH was always increased. And the appropriate microwave radiation could also improve FA.The test results showed that with the optimal dosage for the single conditioning of CPAM ?80mg/L?, the SRF and the water content of vacuum filtration reduced by 81.60% and 9.34% respectively, but the RH and FA increased to 86.86% and 38.36% separately. With the increasing of dosage, the D₃ of sludge floe was continuously reduced, but D₂ and FS was increased and the latter altered obviously.The dewaterability was significantly improved with the conditioning of microwave combined with flocculant, where CPAM plaved a kev role in sludge dewatering. Different from microwave conditioning, with the radiation time extension and the same CPAM dosage, the particle size distribution was declined, but D₃ and D₂ were both increased. The RH, FS, FA under microwave combined with flocculant conditioning were both higher than separate flocculant conditionings.The larger d_0.5 and the denser floe structure, the better dewaterability of sludge. The key factors affecting SRF were particle size, fractal dimension and flocs strength in microwave conditioning. Under microwave combined with CPAM conditioning, the SRF and moisture content of filter cakes were reduced firstly and then increased with increasing of do.s. With the increase of flocculant dosage, the more osteoporosis of sludge floc, the larger porosity were found, but the smaller D₃ and SRF. SRF was decreased by the alteration of FS within a certain range, and the increasing floc strength was conducive to sluge filtration, but the strongest flocculent structure doesn't always mean the biggest dewater efficiency. The key factors in microwave conditioning combined with CPAM influenced SRF as well as d_0.5, D₃ and FS. The models of dewatering characteristics under different sludge pretreatments were built with the tool of SPSS statistics ?V17.0?, and the multiple linear regression models between structural parameters and SRF were proposed separately for the two conditioning methods. The model results showed that the d_0.5 was the crucial factor to improve dewaterabilitv capability of sludge.