Research On The Technology And Mechanism Of Sludge Treatment

As a mixture consisted of pathogenic microorganism, different pollutants and heavy metals, sewage sludge mainly comes from municipal sewage treatment plant, the city waterworks and urban drainage systems. The sludge particles are tiny with a great scope of size distribution and a large resistance and viscosity has made it difficult to separate from the liquid, leading to an unsatisfactory dewatering efficiency for the urban sewage treatment. This will also increase the difficulty in the following sludge treatment steps and its reutilization. Meanwhile, as the sludge contains amount of poisonous and harmful material which is easy to be degraded to produce effluvial smell, it may cause serious pollution to atmosphere, water and soil. This is much more serious especially when it comes to the heavy metals which can cause major damage to the health of human and animals through food chain. Therefore, the improvement on the performance of sludge dewatering, the removal of heavy metal and the elimination of odorous gases have always drawn much attention from related researchers.In the presented paper, sludges from three cities, varied in iron content, were selected for further experiments, in order to improve its performance of dehydration. The results showed that for sludge containing iron content less than 4%, 81% of water could be removed after it was treated by adding some FeSO₄·7H₂O, H₂O₂ at 4% and H₂SO₄ at 2%, under 95°C for 40 mins by traditional heating (only 4 mins by microwave) with the liquid-solid ratio of 0.5 mL/g, while sludge with more than 4% iron content could achieve the same dewatering efficiency at unchanged conditions except for the absence of FeSO₄·7H₂O. Meanwhile, the average for heavy metal removal efficiency is about 75% and deodorization efficiency is obvious.Reduction, detoxification and reusing of sludge can be realized by using this technology, which will cost much less in the following states due to the absence of pollution, removal of water, odor, heavy metal and realization of recycling, while at the same time a new derection for recycling of sludge was developed.