Experimental Study On Remediation Of Ammonia Contaminated Groundwater By Permeable Reactive Barrier

The issues of groundwater pollution are paid more attention recently and ammonia nitrogen contaminated groundwater is an attractive problem. Biodegradation is a traditional and efficient way of removing the ammonium to nontoxic water and nitrogen, but the final effect is limited for the diversity activity of microbe in different environment. A promising material, zeolite, has higher adsorption characteristics for ammonium ion as a cheaper natural mineral in groundwater remediation. However it does not remove ammonium completely through the physical adsorption process. Herein, we proposed to use zeolite and microbe to treat ammonium contaminated groundwater for in site remediation by Permeable Reactive Barrier (PRB).Nitrification experiments were conducted and we got the information about the suitable environment for microbe living condition, degradation rate and degradation cycle. Various oxygen-releasing compounds (ORC) were synthesized and oxygen was measured to meet the microbe demands. It's important to observe the change of pH variation and effect of phosphate on microorganism in releasing oxygen process. Finally, column experiments were used to let the groundwater flow though the ORC column and zeolite column and to study adsorption with biodegradation for groundwater remediation. These results can supply guidance for lateral pilot experiment, such as oxygen-releasing materials selection, microbial bio-film, PRB design. The results are as follows.1, Under the condition of ammonium initial concentration of 15-20 mg/L and dissolved oxygen (DO) of 8-10 mg/L, the growth cycle of microorganism is adaptation period of 1-2 days, growth period of 2-4 days, mature period of 4-8 days and decline period of 8 days later.2, Adding certain proportion of phosphate to ORC, it not only decrease the pH of the system, but also supply nutrition (phosphate) to promote microorganism growth and make the microorganism get into mature time 2 days in advance. In addition, ORC also can persist to supply oxygen and keep the DO of the system sustain 10 mg/L. Because nitrification process can produce mass hydro ion, pH shows a downward trend with the active nitrification.3, Column experiments showed that the change of pH and accumulation of nitrite and nitrate can be used to estimate the forming time of microbe. Nitrite sets out to accumulate at 17 days and reaches stabilization after 27 days. The nitrate concentration appears stable accumulation at the same time. Considered the decrease of pH in the process, the forming time of microbe can be estimated 27 days.