Research on Characteristic of Fe²⁺/S₂O^2-<sub style="margin-left:-7px;">8</sub>Composite CaO Synergetic Conditioning for Municipal Sludge

For the problem as high energy consumption and sludge increment during the municipal sludge management process with advanced oxidation technology of sulfate radical, the Fe2+/S2O2-8 composite CaO reaction system was set up. Meanwhile, systematical studies had been carried out for coordinated conditioning of municipal concentrated sludge. The scientific process parameters were determined with the help of sludge capillary suction time, sewage sludge moisture content and other core indicators and the effect of traditional polyacrylamide flocculation method, Fenton method and activated persulfate method were compared. The results showed that in the neutral concentrated sludge conditioning, there were outstanding advantages for Fe2+/S2O2-8 composite CaO reaction system compared with Fenton, CPAM, and SO-4 methods and the optimal parameters for dosage were as follows: Fe2+/S2O2-8: 80 - 120 mg·g-1 DS, n(Fe2+):n(SPS) = 0.8:1, CaO: 200 mg·g-1 DS. To achieve similar performance index, the dosage of Fe2+ per ton for sludge could be reduced by 20%, the loss rate for iron in filtrate was 0.5%, dewatering of sludge by suction filtration was within 50 s and the moisture content for dewatering cake was 53.7%, which significantly improved the economy and practicability of SO-4 advanced oxidation technology, and the results were expected to form a useful supplement to the popularization and application of SO-4 advanced oxidation technology.

Experimental Study on Granular Sludge Cultivation Based on IC Reactor

[Objective]We aimed to discuss the optimal conditions of sludge granulation on the basis of IC reactor.[Method]By using the formulated glucose wastewater,we studied the rapid cultivation of granular sludge as well as its influencing factors,so as to discuss the optimal conditions of sludge granulation.[Result]Through the static culture outside of IC reactor and dynamic culture in IC reactor,granular sludge appeared within a training cycle,with particle size of 1.0-1.5 mm.In IC reactor,when COD concentration of influent water was 5 000 mg /L,rising velocity was 0.9 m /h,pH was around 7,and auxiliary materials (like flocculant and active carbon) and mature granular sludge were added to the actor during the training process,the granulation process of sludge was accelerated.[Conclusion]The research could provide references for the rapid start-up of IC reactor.

Differences in rheological and fractal properties of conditioned and raw sewage sludge

Rheological tests for raw and conditioned activated sludge （AS） or anaerobic digested sludge （ADS） show that power-law relationships can be used to describe the evolution of several rheological parameters, i.e., limiting viscosity （η∞）, yield stress （τy）, cohesion energy of the sludge network （Ec）, and storage modulus （G＇）, with total suspended solid （TSS） content in raw and conditioned sludge. A gel-like structure that behaves similar to weak-link flocs/aggregates was observed in AS and ADS. As derived from the double-logarithmic plots of G＇-TSS content, the mass fractal dimensions of the raw and conditioned AS or ADS flocs/aggregates were 2.70 and 2.53 or 2.85 and 2.79, respectively. The theological tests also indicate that both polymer conditioning and increased TSS content led to improved elastic behavior, cohesion energy, and yield stress of the sludge network, as well as expanded the corresponding linear viscoelastic range. The porosity of AS or ADS flocs/aggregates will be improved by polymer conditioning.

Improvement of sludge dewaterability with modified cinder via affecting EPS

The relationship between the improvement of sludge dewaterability and variation of organic matters has been studied in the process of sludge pre-conditioning with modified cinder, especially for extracellular polymeric substances （EPS） in the sludge. During the conditioning process, the decreases of total organic carbon （TOC） and soluble chemical oxygen demand （SCOD） were obviously in the supernatant especially for the acid modified cinder （ACMC）, which could be attributed to the processes of adsorption and sweeping. The reduction of polysaccharide and protein in supernatant indicated that ACMC might adsorb EPS so that the tightly bound EPS （TB-EPS） decreased in sludge. In the case of ACMC addition with 24 g·L^-1, SRF of the sludge decreased from 7.85 × 10^12 m·kg^-1 to 2.06× 10^12 m·kg^-1, and the filter cake moisture decreased from 85% to 60%. The reconstruction of ＂floc mass＂ was confirmed as the main sludge conditioning mechanism. ACMC promoted the dewatering performance through the charge neutralization and adsorption bridging with the negative EPS, and provided firm and dense structure for sludge floc as skeleton builder. The passages for water quick transmitting were built to avoid collapsing during the high-pressure process.