Study On Low Turbidity Micro-Pollute Water By Enhanced Coagulation Of Recycling Sludge Process And The Floc Dimention Characteristics

Surface water sources in southern of China including rivers, lake water, reservoirs water, the lakes and reservoirs water as the typically low turbudity micro-polluted source water, have a lower suspended particles concentration, smaller particle size, and higher organic matter and ammonia, and also contain some olfactory and taste, so efficiency of collisions between particles are lower, the effect of coagulation is poor, more pharmaceutical consumption is needed, and a large of sludge production is raised, which brought a great challenge to the conventional process. In order to ensure the safety and effectiveness of treatment of drinking water, it is important to strengthen treatment the low turbidity micro-polluted water. The sludge in sedimentation tank at the purification plant contained a section of insoluble metal hydroxides with adsorption, which can increase the concentration of particulate matter in the raw water, research has shown that, sludge return process may have a enhanced treatment effect on the low turbudity micro-polluted water. The flocs surface shape and internal particles is highly irregular, self-similarity and scale invariance in flocculation process, so the flocs morphology and structure have fractal charactristic. Currently, people are still lack of sufficient knowledge of the interaction between each influencing factor in flocs reaction process and the change of flocs morphology and structure changed. Fractal theory provides a powerful tool to further research on the improvement of flocculation process and flocculation mechanism.This study takes low turbidity micro-polluted water as the research object, compared conventional process with sludge reflow process under different PAC(Polyaluminium Chloride, PACl) dosage for the removal of turbidity, organic matter, and analyzed the change of floc fractal growth characterisics dimension under different coagulation mechanism through static test and CCD camera system recording the particle morphology and structure in flocculation reactor; Investigated the influence of Coagulant dosage, polymer coagulation aid(PAM) and reflux ratio on turbudity, UV254, CODMn and the evolution of floc morphology and structure in sludge return process, the ability of sludge return process to resist water quality and hydraulic shock loads, and the effect of adsorbents, pre-oxidation and pre-oxidation joint adsorbents on turbudity,UV254 and CODMn of sludge return process, and the evolution of floc morphology and structure in recycling sludge process. Experimental results were as follows:1. The results of the comparative experiments between conventional process and sludge return process under different coagulant dosage showed that under certain conditions, sludge return process can reduced sludge coagulant dosage and sludge production, and when the dosage of PACL was 0.04 mmol ? L-1, sludge ruturn process can enhanced coagulation effect on the turbidity, UV254 and CODMn removal, and can generated large and dense flocs, improved the sedimentation performance; Adding PAM can increased the density of floc, improved the average particle size and strengthen the strength of floc, improved flocculation.When the reflux ratio ranges from 1% to 4%, the sludge return process has enhanced Effect on pollutants remove, and the flocs have a higher density, bigger particle size, and better floc settling properties, Floc particle size distribution is approximately normal distribution.2. Sludge reflow process not only have a different treatment effect on turbidity and organics, but also have a great impact on flocs structure and morphology under different impact load, when the initial turbidity of raw water ranges from 20 NTU to 60 NTU, the lower of the initial natural organic matter content and the initial pH ranges from 7-8, and the hydraulic stirring in a suitable conditions, the effect of Enhanced Coagulation are better, the density of the flocs are higher, the particle size are larger in sludge reflow process, floc particles are more uniform, and distributed more concentrated.3. The results of the experiments about comparing powdered activated carbon(PAC), zeolite and magnetite combined process found that the turbidity and organic matter removal are the best in PAC-return sludge combined process, the flocs fractal growth characterisics dimension were the biggest, growth rate is the fastest, coefficient restitution was the highest after flocs crushing in the flocculation process, and floc particles are uniform and centralized.4. The particular size and fractal growth characterisics dimension of flocs can reflect the changes of flocs structure and morphology, can sensitively reflect the influence of hydraulic and water quality conditions change on the flocs Growth characteristics in the growth process, can be used to reflect improve flocculation effeciency, but when the coagulation conditions, impact load, Residual turbidity change in a small range, flocs growth fractal growth characterisics dimension can not sensitive manifested.