The treatment of industrial wastewater can effectively protect the water environment and maintain sustainable development. This paper introduces an incremental proportion and integration (IPI) control algorithm-based programmable logic controller (PLC) used to adjust the aeration tank's dissolved oxygen content automatically in the wastewater treatment process. The control algorithm was improved by a back-propagation neural network (BP-NN). An instance analysis was carried out on a wastewater treatment plant in Zhejiang Province, China. This showed that the BP-NN improved control algorithm made the aeration tank's dissolved oxygen content more stable at the set value than it was with manual adjustment and the conventional algorithm. The total nitrogen content in wastewater treated in the aeration tank under the control of the improved IPI algorithm was minimized and fluctuated least. The aeration tank blower's power consumption was also at its lowest under the control of the improved IPI algorithm.
Sludge dewatering has become an important issue in the sewage treatment industry. The essence of mechanical dewatering is the consolidation and drainage of sludge. Therefore, it is of great significance to study the consolidation characteristics of sludge to improve the dehydration efficiency. Consolidation tests were carried out on the sludge treated with FeCl3 and Fenton reagent, and the consolidation and permeability characteristics of the treated sludge were studied. The sludge shows ultra-high compressibility. The consolidation coefficient of the untreated sludge is 10−7∼10−6cm2/s. After adding 15% FeCl3 (relative to sludge dry weight), the consolidation coefficient of the sludge increased by 5∼8 times, and reached 10−6∼10−5cm2/s after Fenton reaction treatment. The untreated sludge has obvious time deformation characteristics.
The solidification technology can meet the requirements of landfill by enhancing the sewage sludge strength. The solidified sludge strength would be decreased by landfill leachate action because the acid could dissolve the hydrated materials. Chemical kinetics equation was obtained by reaction order α, β and rate constant k, which reflected the acid effect on hydrated materials by Ca2+ and were got based on the laboratory experiments. The research results showed that the strength loss could be neglected in engineering because pH value of leachate possessed less impaction on solidified sludge strength. Moreover, after adding clay minerals, the strength loss is smaller and the buffering capacity is stronger.
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