Experimental Study On The Inhibitory Effect Of Filter Capping Combined With Immobilized Microorganism On Pollutants Release From Sediments

Landscape water, which has a closed relationship with human's daily life, is considered to be an important evaluation index of the urban cultural environment. Currently, an increasing water quality deterioration in landscape water has seriously affected people's production and life, especially in water eutrophication. However, even through the external source pollution is controlled, the endogenous pollution induced by the sedimentary pollutants release, such as nitrogen and phosphorous, can also accelerate water degradation and become the main reason for water eutrophication. Therefore, contaminated sediments repair should be the critical path to solve this problem.By taking the contaminated sediments in Yang-zhou Canal as the research object, the experimental simulations were carried out. In this study, the technology of filter capping combined with immobilized microorganism was applied to inhibit the pollutants migration from sediments to overlying water in order to prevent water eutrophication effectively, meanwhile, a variety of efficient microbial populations were constructed to reduce nitrogen load for in-situ bioremediation of contaminated sediments. The results show that:(1) Three strains of denitrifying bacteria and three strains of nitrification bacteria were isolated from Yangzhou canal sediment through repeated screening and purification: 9#-3,9#-6,9#-21and 1#-4,1#-5,3#-6. Ammonia nitrogen removal rate of nitrifying bacteria 9#-3,9#-6,9#-21 are: 75.58%, 59.83%, 65.08%. denitration nitrogen removal rate of denitrifying bacteria1#-4,1#-5,3#-6 are: 79.83%, 71.18%, 79.35%. Then the three strains of high efficient denitrifying bacteria and three strains of high efficient nitrification bacteria strains were mixed into many different combinations, the highest efficient combination was I:(1#-5)+(3#-6)+(9#-3)+(9#-6)+(9#-21),and the denitrifying bacteria, denitrifying bacteria volume ratio is 1:1. the highest total nitrogen removal rate can reach 78.44%. The highest efficient combination I will be immobilized microorganism layer repair experiment using bacteria in the next step.(2) The removal rate of ammonium by zeolite is more than 90% and the removal rate of ammonium by zeolite-microbe combined immobilization technology can reach 94.64%. The process of ammonium adsorption by the zeolite is in accordance with Langmuir adsorption isotherm. The maximum adsorption content of ammonium by zeolite is 4.761905mg/ g; 25℃enhanced ammonium adsorption onto zeolite, and the removal rate reached 92.1%; the main way of removing ammonium by zeolite is ion exchange. Desorption rate of the KCl solution on zeolite is higher than CaCl₂ solution and NaCl solution at different initial concentration of ammonium; Experiment preliminarily determines the zeolite (no biofilm) maximum dosage: in 25℃, 4.2kg/m²; in 15℃6.9 kg/m². Their highest total nitrogen removal rate are over 80%.(3) In 25℃, through comparing effects of inhibiting sediment pollutants using the different technical means: cover filler, covering filler combining immobilized microorganism, dosing 1% of predominant bacterium fluid, dosing 0.5% of predominant bacterium fluid, we know covering filler combining immobilized microorganism technique have more apparent denitrification effect than others, total nitrogen highest inhibition rate can reach 72.22%. This technique is through the formation of biofilms of ammonia nitrogen of biodegradable to make zeolite orthotopic clean renewable, thus achieved the in situ inhibiting ammonia nitrogen releasing from sediments, and denitrification reduce sediment nitrogen load. Through comparing experimental results of covering zeolite of different density to suppress the sediment of pollutants, we know when zeolite cover density is 3.3 kg/m², denitrification effects is better and total nitrogen highest inhibition rate can reach 73.86%.(4) In 15℃, through comparing effects of inhibiting sediment pollutants using the different technical means: covering filler combining immobilized microorganism, dosing 1% of predominant bacterium fluid, we know covering filler combining immobilized microorganism technique have more apparent denitrification effect than others, total nitrogen highest inhibition rate can reach 77.28%. Through comparing experimental results of covering zeolite of different density to suppress the sediment of pollutants, we know when zeolite cover density is 5.0 kg/m², denitrification effects is better and total nitrogen highest inhibition rate can reach 78.26%.