Biodegradability Of Major Papermaking Chemicals

The composition of papermaking wastewater was complex and toxic, so it was one of themain water pollution. It was difficult to handle the papermaking wastewater. The study selectedrepresentative chemicals as retention and filter aid (CPAM), wet strength agent (PAE) and sizingagent (AKD) to research on the biodegradability of these chemicals in activated sludge.Firstly trained the activated sludge. Added nutrient solution everyday according to theproportion of COD:N:P=100:5:1andC/N=20. At the same time the activated sludge keeped thecontinuous aeration. Microscopy and monitor the SV, MLSS, SVI and the COD value everyday.As training there appeared a lot of strip zoogloea and vorticella. The SV, MLSS and SVI of theactivated sludge increasing and stabilized at last. The SV of the activated sludge stabled at30%,the SVI of the activated sludge stabled at50~60ml/g, the MLSS of the activated sludgefluctuated in a small-scale nearby6.5mg/L, the pH of the activated sludge varied between6.5and8.5. At last the COD removal rate stabilized at88%, indicating that the activated sludge hadbeen successfully trained.Secondly domesticated the activated sludge. Added chemicals as10mg/L,20mg/Lincreased to50mg/L, and the daily dosage of nutrient solution was same, besides the activatedsludge keeped the continuous aeration. When the activated sludge formed large floc particleswith closely structure and the measured SV, SVI, COD index was stable, it seemed that theactivated sludge had been successfully domesticated. When the domestication finished the pH ofthe activated sludge containing CPAM was near7.0, the SV was near55%, the MLSS was near7.0mg/L, the SVI was near80ml/g, the removal rate of COD stabilized at about75%. The pHof the activated sludge containing PAE was near6.8, the SV was near60%, the MLSS was near10.5mg/L, the SVI was near50ml/g, the removal rate of COD stabilized at about62%. The pHof the activated sludge containing AKD was near6.3, the SV was near58%, the MLSS was near6.8mg/L, the SVI was near55ml/g, the removal rate of COD stabilized at about61%.Finally analyzed the biodegradable of the chemicals. Explored CPAM concentration, pH,sludge concentration, idle time on the influence of the removal rate of CPAM with theorthogonal experiment was concluded that the best processing conditions for degradation ofCPAM was idled for1h, namely aerated for2.5h then stopped for0.5h, repeated2cycles, the CPAM concentration for60mg/L, sludge concentration for5g/L, pH at7.5. This moment, theremoval rate of CPAM would reach56%. IR spectrum showed that there were not any CPAMadsorbed on the activated sludge. At last the wastewater containing CPAM still belonged to thebiological wastewater. The removal rate of PAE would reach47.0%. IR spectrum showed thatthere were not any PAE adsorbed on the activated sludge. At last the wastewater containing PAEstill belonged to the biological wastewater but the biological was poorer than the wastewatercontaining CPAM, may be PAE was degraded into another product that made the COD increased.The removal rate of AKD would reach60.2%. IR spectrum showed that there were not any AKDadsorbed on the activated sludge. At last the wastewater containing AKD still belonged to thebiological wastewater but the biological was poorer than the wastewater containing CPAM,better than the wastewater containing PAE. AKD was unstable, most of it would be hydroliedinto palm ketone.