Improving Water Quality Of Waihuan River In Tianjin By Additive Microorganisms

With the development of economy, urban river in China is polluted more and more badly and the ecological environment is becoming worse, so that the shortage of water resource is aggravated. Therefore, an effective method is needed to maintain the balance of water. Additive microorganisms is considered to be an important way of preventing and repairing natural water pollution because this technology is effective, simple, economical, without secondary pollution etc.For practical application of improving water quality of Waihuan River in Tianjin by additive microorganisms, this paper mainly studied optimum dosage of cultures, optimum condition of mixed cultivation and optimum dosage of mixed microbial inoculum. What's more, it contrasted the two addition scheme through static experiment.Adoptive microorganism is actinomyces, yeast, Bacillus subtilis, lactic acid bacteria, flocculating bacteria. Yeast with the maximum COD removal efficiency was used as the primary microbe to biodegrade COD, actinomyces and lactic acid bacteria with the maximum ammonia nitrogen removal efficiency were used as the primary microbe to biodegrade ammonia nitrogen. Bacillus subtilis and flocculating bacteria were used as the accessorial biodegradation microbes.Firstly, it studied optimum dosage of primary biodegradation microbe by response surface methodology. Dosages of yeast, actinomyces and lactic acid bacteria were selected as three factors. After optimization analyzing by Minitab software, COD and ammonia nitrogen removal efficiency both reach maximum. Based on optimum dosage of primary biodegradation microbe, optimum dosage of accessorial biodegradation microbe was defined by addition different contents of accessorial biodegradation microbe. It was gained optimum dosage of cultures: yeast 0.725mL, actinomyces 1.355mL, lactic acid bacteria 2.250mL, Bacillus subtilis 0.215mL, flocculating bacteria 0.215mL(OD660=0.5, volume of raw water is 100mL), COD removal efficiency was 50.5%, ammonia nitrogen removal efficiency was 62.3%. Then, mixed cultivation of cultures was studied, medium for mixed cultivation was as following: brown sugar 5g/L, NH₄Cl 0.5g/L, KH₂PO₄ 1.3g/L, Na₂HPO₄ 3.2g/L, MgSO₄·7H₂O 0.2g/L; culture time was 49h; optimum temperature was 30℃; optimum pH was 7. Finally, COD and ammonia nitrogen removal efficiency of mixed microbial inoculum was studied and the results were summarized in the following: optimum dosage of mixed microbial inoculum was 3.5mL (dry weight of culture was 17.5mg), COD removal efficiency was 49.6%, and ammonia nitrogen removal efficiency was 61.3%. Although COD and ammonia nitrogen removal efficiency is decreased with the mixed microbial inoculum, it not only reduced the quantity of inpouring culture, the cost, manpower and material resources, but also simplified the making way.