Wastewater treatment of calcium hypochlorite bleached pulp
1. The ultrafiltration method is not easy to be decomposed by microorganisms because of the high molecular weight part of the bleaching waste solution.
Therefore, ultrafiltration was considered before biological treatment.
Ultrafiltration can remove 50%-90% of the organochloride or AOX in section E wastewater, but the chlorophenol compounds with low molecular weight are the most toxic components of AOX, so the ultrafiltration efficiency is very low, but then biological treatment can remove 62%-90% of AOX.
2. By chemical sedimentation, iron salt or aluminum salt can precipitate organochloride to remove AOX.
The use of Polyethyleneiminc can also make the chlorination and alkali treatment stage of the organic deposition down, the chlorination section of AOX removal rate of 54%-84%.
The alkali treatment stage is 50%-73.
(3) oxidation process
1) during the aeration process of ultrasonic oxidation, the low-molecular weight chlorinated organics such as - chlorophenol, dichlorophenol and trichlorophenol can be removed by ultrasonic treatment for 1h.
2) ozone, ultraviolet radiation and powdered activated carbon were oxidized alone or in combination.
The removal rates of the low molecular weight TOX were respectively
32.2%--43.7%, 18.7% -- 78.7%, and 10.2% -- 53.0%, respectively. The total TOX removal rates were 82% -- 86%, 47% -- 48%, and 73% -- 74%, respectively.
Oxidation by ultraviolet irradiation alone can be called photolysis. Photolysis mainly involves the decomposition of high molecular weight AOX into C1- under the action of UV.
3) oxygen oxidation of bleaching wastewater in E stage can significantly remove TOCL and chroma. Lignin chloride degradation is the strongest in the early stage of oxygen treatment, which plays an important role in the removal of TOCL and chroma.
Alkaline hydrolysis alkaline hydrolysis is the use of various basic compounds and lignin chloride reaction.
Methods to promote AOX reduction in waste solution due to different alkaline compounds or different combinations.
The ability of AOX to reduce waste liquid is also different, usually NaOH/Ca(OH)2 or Na2S, Na0H and Ca(0H)2 combination to reduce AOX.
Reaction time - certain, high PH value, high AOX removal rate in the mixture.
5. Unconventional biodegradation method waste solution unconventional biodegradation method.
At present basically is to use fungus, especially the fungus that decomposes lignin, commonly used white rot, it can degrade chlorinated lignin, but need to add carbon source to produce peroxidase, degrade lignin PH value, nutrient salt, dissolved oxygen, contact stay time to affect its effect.
6. Electrolytic treatment electrolytic treatment USES electrodes of different compositions to conduct electrolysis at different times to obtain the required AOX removal rate. At the highest AOX removal rate, the AOX removal rate can reach more than 99%.