Experimental Study On The Improvement Of River Water Quality By Microbial Enhanced Gravel Bed Under Aeration Condition

Traditional river aeration technology can improve river dissolved oxygen in a short time, accelerate the restoration of river ecological environment, have a good feasibility and superiority in control of river pollution. This research tried to combine adding engineering bacteria, gravel contact oxidation technology and river aeration technology, to develop a new technology with long term effect on river channel treatment. The main research contents and conclusions are as follows:(1) Compared 0.33 m3/m2·h?1.66 m3/m2·h?3.33m3/m2·h three kinds of aeration intensity, the result showed improving aeration intensity can improve water treatment effect. Considering the economic benefits, the best choice is 1.66m3/m2-h. Under this situation, after 78h the concentration of CODMn?NH3-N reduced from 16.6mg/L and 11.8 mg/L to 11.2mg/L and 8.37mg/L. Comparing water quality and economic effect, the optimum dosage is 500mL/t, after 7 days the concentration of CODmn?NH3-N decreased from 18.2 mg/L and 8.03 mg/L to 10.1 mg/L and 5.69 mg/L. Adding engineering bacteria under intermittent aeration conditions, after 7 days CODmn?NH3-N decreased from 17.3mg/L and 8.29 mg/L to 6.6 mg/L and 5.63 mg/L.(2)Compared 30cm,50cm,and 80cm gravel height, the result showed improve gravel height can improve the water treatment capacity.80cm gravel height could reduce the concentration of CODMn> NH3-N from 18.6mg/L and 10.3mg/L to 9.37mg/L and 6.09mg/L. Comparing 0.5m/h?0.25m/h?0.125m/h three different velocity, the result showed that purification effect is better when velocity is slow. When the velocity is 0.125m/h, CODMn? NH3-N decreased from 17.8mg/L and 8.77 mg/L to 11.9 mg/L and 6.88 mg/L(3)Long time running results showed that this technology can have at least 25d treatment effect, in this period, CODMn and NH3-N removal percentage were 27.3%-47% and 10.9%-33.4%. Winter running(minimum temperature o f-3??8?) results showed the effect of various measures were declined. Simple aeration CODMn and NH3-N removal rate were about 20%, adding engineering bacteria had little effect to CODMn removal, but 25% removal of NH3-N. Biofilm gravel bed had only 10% removal percentage of both CODMn and NH3-N.(4)Analyzed the specific situation of the Park River in YiXing, with the gravel bed (50cm), intermittent aeration (2h/d), engineering bacteria (one-time dosing 500mL/t), calculated the total oxygen demand of Park River by using the first order reaction box model was 7.6kgO2/d, the project investment was about 92k Yuan, project operation cost is 73.08 Yuan/day. The same type of river restoration project investment costs about 800k Yuan/km, operation cost is 635 Yuan/(d·km).