The Research On Water Reaeration Technology For Urban Hard River

In this paper, a research on arrangement the relative position of the three kinds of aeration technology is studied, by studying the effects of reaeration and removal of pollutants, influence factors of the photosynthesis of aquatic plants,microporous aeration technology, and hydraulic reaeration technology. The study is aimed at the problem of urban hard river closely related to water hypoxia, such as the deterioration of water quality, weak water self purification ability etc. This paper puts forward the arrangements of reaeration technique, and provides technology support for water purification in urban hard river.The main conclusions of the study are:(1)Four native submerged plant, Hydrilla verticillata, Ceratophyllum demersum,Vallisneria spiralis, and Myriophyllum spicatum in natural light conditions through photosynthesis have reaeration effect on water. The order Of water reaeration effect from good to bad is Hydrilla verticillata, Vallisneria spiralis,Ceratophyllum demersum and Myriophyllum spicatum. Hydrilla verticillata, Ceratophyllum demersum, Vallisneria spiralis and Myriophyllum spicatum have good removal rate of ammonia nitrogen in water, and Hydrilla verticillata has the best effect among them. Effect on removing COD in the water of the four kinds of aquatic plants are not obvious,and the growth status of aquatic plants influences their removal effect of pollutants.(2)Through laboratory experiments of microporous aeration technology reaeration ability, the main conclusions are as follows: The required aeration time DO in water reached a stable value is negatively correlated with aeration intensity, and positively aeration depth. The DO in water near aeration point in four hours can reach more than 6mg/L. The water reaeration effect of microporous aeration technology is no difference in the vertical direction, and gradually decreases in the transverse direction. The removal effect of COD and ammonia nitrogen is no difference in the vertical direction. Microporousaeration measures on hard river have very low removal rate of COD and ammonia nitrogen. In the depth range of 0.3m-0.7m, and aeration intensity of 200L/( ㎡ ·h),Microporous aeration in continuous operation and intermittent aeration(40 min aeration, static 20 min, alternately) operating conditions can increase water DO to more than 6mg/L, to meet the objective needs of microporous aeration reoxygenation in 3h. In the most unfavorable water depth of 0.7m under the condition of intermittent operation, water DO decreases gradually after stopping aeration at the rate of 0.0249 mg/(L·min)with time.(3)The effect of water drop reaeration measures on hard river on the whole is positively correlated with the falling height, water flow, and water depth, but negatively correlated with the concentration of DO. Hydraulic water drop reaeration measures have very poor removal effect of ammonia nitrogen and COD.(4)On the basis of studying the reaeration effect of microporous aeration,hydraulic drop, aquatic plant photosynthesis, this paper puts forward five kinds of reoxygenation arrangement of A, B, C, D, E making the water DO reach above6mg/L, compares economy of various layout from microporous aeration duration and recommends operating mode for the hard river reaeration technique in practical engineering applications.