Design Of The Photoelectric Detecting Device For Leather Waste Water COD

According to traditional chemical methods for COD (Chemical Oxygen Demand) measurement has the defects of complicated operation, easy to produce secondary pollution, and combining with the industry background that the leather enterprises in Zhejiang is concentrated currently, they producing large amounts of industrial waste water what containing high concentrations of COD every year, this paper put forwards to apply the 282nm characteristic wavelength method with advantages of fast detecting, high accuracy on leather waste water COD measurement, and design a device to achieve its detecting automatically. In addition, makes use of ultraviolet spectroscopy instead of traditional chemical methods can calibrate the COD prediction model quickly and environmentally, improves the reliability of the device further. This device is suitable for popularity in the enterprise has with its low cost of running and high accuracy of detecting. The main contents of this paper are as follows:1 Introducing the research results about detecting system of water quality at home and abroad, combining with traditional COD’s measurements, exploring the feasibility and significance about designing a photoelectric device what detecting by characteristic wavelength and calibrating by ultraviolet spectroscopy for leather waste water COD.2 Design a photoelectric detecting device for leather waste water COD, it including four parts:optic detecting system, sampling and processing system, electrical control system and PLC control system. Completed components’ selection and combination for the optic detecting system, utensils’design and mechanical installation for the sampling and processing system, achieved an electrical control for optic detecting and waterway’s processing in accordance with the detecting requirements and finished a design of software and hardware for the PLC control system, made it debugging and simulating finally, verified the device could be running automatically.3 Divided the waste water from different leather enterprises of Wenzhou, Lishui of three parts after diluting for different proportions. Detected their COD concentration by national standard method, detected their spectral absorption peak area by ultraviolet spectrum scanning and absorbance by the characteristic wavelength. Then established two prediction models based on the data and made use of ultraviolet spectroscopy instead of traditional chemical methods to calibrate the COD prediction model.4 Examined the precision of the models. Detected 16 leather waste water COD by the two prediction models and compared results with the national standard method, errors do not exceed 5%, showed that the two methods have a high accuracy and the detecting results of this device is reliable.5 Applied characteristic wavelength method on the absorbance detection of several other industrial waste water COD, got the analogous conclusions. Then explored the impact of temperature, turbidity, pH on characteristic wavelength, at last, put forward the property, the possible reasons of the errors and some further improvements of this device.