| Black and odorous water has become one of the environmental problems that threaten the health of residents and affect social development.As the source of endogenous pollution of black and odorous water,the sediment accumulates a large number of pollutants,so improving the sediment characteristics is one of the important measures to control black odorous water.Calcium peroxide(CaO2)is a commonly used oxygen-releasing compound,but the rapid release of oxygen in response to water does not meet the long-term slow release of oxygen required for engineering applications.In this study,CaO2 was used as the oxygen source,zeolite was used as the filler,and environmentally friendly material polylactic acid was used as the embedding material to prepare a CaO2 slow-release oxygen agent with slow release of oxygen.Through the clean water experiment and the simulated black odor water sediment improvement test,the effects of the embedding material ratio,the muddy water environment temperature and the different dosage positions of the slow release oxygen activator on the oxygen release rate and the improvement of the sediment characteristics were investigated.The following conclusions were drawn:(1)Scanning electron microscopy confirmed that polylactic acid can effectively entrap CaO2.The slow release oxygen and powder CaO2 were added to the oxygen-free water with a pH of7.12.The oxygen release rates were 0.18 and 0.973 mg/(L·h),respectively.The pH of the water was 8.9 and 11 after complete oxygen release.Experiments show that slow release oxygen caneffectively slow down the oxygen release rate of CaO2,and the effect on the pH value of water is much smaller than that of powdered CaO2.(2)The proportion of polylactic acid has a certain effect on the oxygen release efficiency of slow release oxygen.The proportion of polylactic acid below 71.4%or higher than 83.3%will lead to a rapid increase of oxygen release rate of slow release oxygen.In the 15-day test,when the ratio of polylactic acid was 83.3%,the slow release oxygen release rate was the slowest,0.521 mg/(L·h),and the removal rate of sediment organic matter was 5.3%and in the sediment.The inhibitory effect on the release of NH4+-N and TP in sediment was obvious.(3)The temperature of the water body and sediment environment is one of the factors affecting the rate of oxygen release from the slow release oxygen agent.When the mud water temperature is higher than 25?,the slow release oxygen release rate was fast,the oxygen release period was short,and when the temperature is lower than 10?,the oxygen release rate was slow and the oxygen release time was long.Considering the removal of organic matter in the sediment and the inhibition of the release of NH4+-N and TP from the sediment in the sediment,it is better to add the slow-release oxygen to the sediment under normal temperature conditions.(4)The addition of slow release oxygen at different locations affects the release of oxygen.The slow release of oxygen on the sediment surface is longer than the oxygen release time in the sediment,and it has a certain inhibitory effect on the release of NH4+-N and TP.(5)In the black odor water sediment simulation test,the dosage of the slow release oxygen agent was calculated to be 543 g/m2 according to the oxygen consumption rate(SOD)of the sediment.After 30 days of testing,the removal rate of sediment organic matter was 20.6%,and the overlying water NH4+-N,TP,COD decreased to 2.12 mg/L,0.408 mg/L,45 mg/L,respectively,and the peak dissolved oxygen of the overlying water was 4.54 mg/L.After 30 days of testing,the dissolved oxygen and pH were 3.7 mg/L and 7.9,respectively,and the color of the sediment changed from black to brown,but the mineralization of heavy metals in the sediment is not obvious. |
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