Study On The Treatment Of High Concentration Morpholine-containing Wastewater

The heterocyclic xenobiotic compound morpholine (C4H9ON) and N-methylmorpholine (C5H11NO) are of great importance for different industrial purposes. They are used as versatiles solvents, rubber additives, anticorrosive agents and in the production of drugs and pesticides due to their chemical nature, being both a cyclic ether and a secondary amine. Due to their xenobiotic natures they often pass through biological treatment processes unchanged and their occurrences in food and drinking water have been reported. Since morpholine and N-methylmorpholine can be chemically or enzymatically modified into carcinogenic and mutagenic N-nitroamine and N-nitrosamine derivatives, their presences in drinking water and food is a serious public health concern. Therefore, it is of great practical significance screening out highly effective morpholine and N-methylmorpholine degradation strains and exploring the effective wastewater treatment process.This study aimed at the organic wastewater containing high concentration of morpholine and N-methylmorpholine, proposing a combined process of aerated stripping-adsorption-biological process, and indoor experiments were made.1,The aerated stripping experiment was made on different stripping time and gas-liquid ratio. The raw wastewater after twice aerated stripping, the concentration of ammonia nitrogen was reduced from 62,500mg/L to 431mg/L, meanwhile COD was reduced from 50,840mg/L to 26,051mg/L.2,It was determined through adsorption experiments that the maximum adsorption capacity of the activated carbon for COD was 198mg/g, and the adsorption equilibrium time was 6 hours. From the activated carbon adsorption removal efficiency and economic cost perspective, the best dosage of activated carbon was 140g/L. Under these conditions, COD of the wastewater was reduced from 26,051mg/L to 2,769mg/L and the concentration of ammonia nitrogen was reduced from 431mg/L to 134 mg/L.3,In biological experiments, strain M and strain JM which can degrade morpholine and N-methylmorpholine were screened out from wastewater and sediment. Strain M can not degrade N-methylmorpholine but morpholine, and strain JM can degrade both morpholine and N-methylmorpholine. After a month domestication, the optimum concentration of the target pollutants were defined. The optimum concentration of morpholine for the growth of strain M in the liquid substrate was 2,000mg/L, and the optimum concentration of morpholine and N-methylmorpholine for the growth of strain JM in the liquid substrate were 2,200mg/L and 2,000mg/L respectively. The strain M was chatacterized as a Gram-positive, catalase-positive, starch hydrolysis-positive, 3-keto–galactose-negative, nitrate reduction-positive, nitrite reduction-negative, denitrification-positive, glucose-oxidation, ball-shaped bacterium, belonged to micrococcus through the preliminary identification. The strain JM was chatacterized as a Gram-positive, catalase-positive, starch hydrolysis-positive, 3-keto–galactose-negative, nitrate reduction-positive, nitrite reduction-negative, denitrification-positive, glucose- fermentation , rod-shaped bacterium, belonged to microbacterium through the preliminary identification. The optimum degradation conditions of the strain M and JM were defined by examining their degradation rates under different pH, the amount of phosphate buffer solution, auxiliary carbon source and the mount of inoculum, and the degradation kinetics experiments were made under these conditions. The experimental results showed that the highest morpholine degradation rate of strain M was got under the conditions of pH 7.5, 1.5mL phosphate, glucose as auxiliary carbon source, 8mL inoculum, reaching 74.5% within 120 hours, and its degradation curve was fit for the first-order kinetics. The highest morpholine and N-methylmorpholine degradation rates of strain JM were got under the conditions of pH 7.5, 3.0mL phosphate, methanol as auxiliary carbon source, 4mL inoculum, reaching 86.8% and 86.1% respectively, and their degradation curves were both fit for the zero-order kinetics.4,In the biological treatment of indoor experiments, the combined process of activated sludge reactor and biological aerated filter(BAF) was used. In the activated sludge reactor system, activated sludge which had higher degradation rate was got after two month acclimation. The removal efficiency of the efluent COD was studied under different pH, DO, HRT and adding amount of the functional strains. The experimental results showed that the removal efficiency of the sedimentation tank efluent COD is the highest when the pH of the aeration activated sludge reactor influent is 7.5, DO is 4.3mg/L and HRT is 30 hours. When the adding amount of the functional strains to the aeration activated sludge reactor is 3.0g/L, the efluent removal efficiency of COD in the sedimentation tank can be achieved 83.1%. In the BAF process, the removal efficiency of the COD was studied under different DO, and when the DO is 3.3mg/L, the removal efficiency of COD is the highest, reaching 55.8%. Continuous monitoring of the biological process was made in the best parameter, when the influent COD was 2736mg/L, the average efluent COD was 387mg/L, and the removal efficiency could reach 85.9%.The efluent COD of the morpholine-containing wastewater was reduced from 50,840mg/L to 387mg/L through this combined treatment process.