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The raw water for the packaging color printing waste water includes the production waste water and the domestic sewage. Normally we use the polyacrylamide as the waster purifying agent. The production waste water is mainly the printing ink waste water and the paste glue waste water, which is about 80% of the total volume. The component of this waste water is very complex which very high COD, but it does not contani the heavy metals and the toxic substances. The domestic sewage is about 20% of the total volume, it is of less pollution and does not have the heavy metals and the toxic and the harmful substances neither. To treat these two types of waste water together comprehensively will help to level the water quality and will facilitate the biochemical treatment. The cationic polyacrylamide can be used in the treatment, it can achieve the clarification and purification effect, the settlement promotion effect, the filtering promotion effect, the thickening effect and the other effects to help the treatment.
The polyacrylamide has been applied as the flocculant for the purification to many industries and fields such as the sewage treatment, the textile industry and the coal industry etc. Among these industries, the sewage discharge of the printing factories is always a headache problem because now the governmental authorities strictly control the discharge of such sewage, therefore, the big -sized printing factories all have set up the sewage treatment system. The polyacrylamide has played an irreplaceable role in the process of these sewage treatment systems.
The pollutants in the packaging color printing waste water are mainly the feculence, the salts, the oil and the fats etc which are attached on the cotton and other textile fibers, and also all kinds of the slurry, the adding dyes, the surfactants, the additives and the alkali etc which are added during the production processing. There are two type of treatment methods for the printing and dyeing waste water, one is the physical method, another is the biochemical method, both are fairly scientific and reasonable.
The polyacrylamide used for the packaging color printing waste water is the cationic polyacrylamide, that is because the content of the impurities in such color printing waste water is relatively high which may require a more complicated treatment processing and technics. Currently, both the physical method and the biochemical method needs the flocculant. According to the characteristics of the color printing waste water, that is the high ink concentration and the high COD concentration, it is required to do the air flotation pretreatment.
The treatment principle of the packaging color printing waste water
The printing ink waste water, the production waste water and the oily waste water firstly will go through a mechanical grille, and then get into the adjusting tank for the homogeneous adjustment after the bigger solid impurities are removed. In the adjusting tank, the water quality and quantity will be regulated, and then the water will be pumped up to the flotation device. Before the flotation device, a dosing system is designed, and the dosing system will put the mixing agent to the water for the solid-liquid separation process. After that, the waste water will go to the sedimentation tank, the sludge will be separated and sent to the sludge drying field for the drying process, while the waste water after the pretreatment will enter the anaerobic regulation tank for the preliminary treatment with the domestic sewage and the dinning hall sewage. After the preliminary treatment, the water will enter the two-stage aeration tank for the aerobic treatment, it will take about 6 to 7 hours for the biological degradation which will further improve the removal rate of the COD and BOD. The sewage sludge mud generated in the biological treatment system will be extracted to the anaerobic regulation tank, using the the microbial digestion sludge decomposition system to reduce the sludge discharge volume.
By the treatment in these processes, the concentration of the COD will be generally lowered to meet the stata emission standard of such waste water.