| This topic is derived from an industry-university-research cooperation, which is hosted by Guangdong University and Technology with Ganghui Industrial Wastewater Treatment Co., Ltd (Foshan City). And, it also combines with the technology improvement of Ganghui sewage plant on treatment printing and dyeing wastewater with high concentration ammonia, then finding a new process technology.In this thesis, it carried out the upgrade project of Ganghui sewage treatment plant before studying new technology processing, which adopted immobilized microorganism technology to process printing and dyeing wastewater with ammonia nitrogen. Combined with the actual situation of the centralized printing and dyeing wastewater treatment plant, the transformation uses two-stage biological treatment process, which is "coagulation and sedimentation+the hydrolytic acidification+coagulation and sedimentation+bio-contact oxidation". With ammonia concentration at400mg/L or less in influent, the upgrade system is running stable and up to drainage standard. But with high concentration of ammonia nitrogen wastewater increased dramatically in the Industrial Park, the upgrade process can never satisfy the requirement of the denitrification process after ammonia concentration up to500mg/L or more.This study finds four denitrification bacteria by enrichment and screening with high purity and good stability, including ammoniated strains, nitrosated strains, nitrification strains and denitrification strains. And it also researches physical and chemical characteristics and physiological feature of them. The results showed that:they are small round translucent wax-like ball grown in solid beef extract-peptone medium, with nitrosation and nitrifying bacteria similar, but the form of anti-nitrifying bacterium difference. And they belong to rod-shaped bacteria. Addition to ammoniated bacteria, other three strains are gram-negative bacteria. The four strains have heat resistance, the growth temperature is38℃, salt tolerance of6%, an obvious movement. Also, they all have strong characteristic of nitrate reduction and starch hydrolysis, especially the nitrifying bacteria and denitrifying bacteria. And they have no the characteristics of catalase reaction but only denitrifying bacteria.With optimizing the component ratio, we found the optimal solution of immobilized microorganism particles preparation, including polyvinyl alcohol (PVA) concentration of 11%, alginate concentration of1%, the activated carbon added concentration of2%, a curing agent is saturated solution of boric acid with4%calcium chloride, the fixed-cross linking time is24h.Adding the carbon source is conducive to the immobilized bacteria on the degradation of ammonia removal. And the efficiency of ammonia removal can achieve the maximum with the right amount of carbon source. But it will retard the speed of ammonia removal with higher content of carbon source in immobilized particles process. In this experiment, the immobilized denitrification technology applies to nitrogen-containing wastewater with the various concentration. It has better treatment effect that the ammonia nitrogen concentration ranging from50mg/L to300mg/L, with higher degradation speeds, as high as90%degradation rate. At the same time, it will achieve better removal by appropriately increasing response time, when the system has higher concentration of ammonia nitrogen in the sewage.Conventional activated sludge method is suitable for dealing with low concentrations of nitrogen-containing wastewater. And it has a better effect for domestic wastewater treatment than printing and dyeing wastewater. In this test, we regard100mg/L ammonia-nitrogen concentration as the drug point of microorganisms in the conventional activated sludge system.Bio-contact oxidation method is suitable for dealing with medium and low concentration of nitrogen-containing wastewater. In this test, we regard150mg/L ammonia-nitrogen concentration as the microbial drug point in the bio-contact oxidation system.It is a significant advantage for the immobilizated denitrification bacteria technology to deal with the various concentrations of nitrogen-containing wastewater, especially in the printing and dyeing wastewater with high concentration of nitrogen-containing.To be protected by the immobilized vector, microorganisms show a certain buffering capacity for higher ammonia nitrogen impact of the external environment. So the immobilized technology has a higher resistance than conventional activated sludge and bio-contact oxidation, which shows stronger load resistance with the higher concentration of ammonia nitrogen wastewater. In this test, we regard400mg/L ammonia-nitrogen concentration as the microbial drug point in the immobilized denitrification bacteria technology.We can combine with multiple biological processes for degrading the wastewater with high concentration of ammonia nitrogen. It can bring technical superiority into full play, and avoid the limitations of a single process. We can choose the immobilized microbial technology to treat the wastewater with high concentration of ammonia nitrogen above200mg/L-400mg/L. And then, the bio-contact oxidation process can be used as the secondary biological treatment, when ammonia concentration is below150mg/L after responding8hours, because the bio-contact oxidation technology is suitable for dealing with nitrogen-containing wastewater with medium and low concentration. In this way, we can reduce aerating reaction time and save operating costs. With low concentration of nitrogen-containing wastewater under100mg/L, we can use the conventional activated sludge process, which is more simple, lower operating costs and better treatment. |
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