Improvement And Optimization Of Permeable Reactive Barrier Technology To Remove Ammonium From Groundwater

Since the pollution of ammonium in groundwater become more and more serious, the remediate method received a wildly attention. The Permeable Reactive Barrier (PRB) technology based on the reaction media zeolite was favored, for the low cost, stable treatment effect, convenient operation, and no power consumption. However, the application was limited, for the adsorption saturation problem of zeolite. In this research, we modified the PRB using different dosages of Oxygen Releasing Compound(ORC), ceramsite and sponge iron particle. And a single-media PRB, a multi-media PRB(M-PRB) and four improved M-PRB(IM-PRB) were designed to select a technology which could not only overcome the defect of zeolite-PRB but also have a good pratical application, using one-dimensional continuous dynamic column to do the research. The research results were summarized as follows:(1) After three stages of "prepared to hang bio-film, started to hang bio-film, and full hanged bio-film", The natural zcolite(NZ) surface was coverd with bio-film, but it’s composition and structure had almost no changes. The growth of bio-film in the surface of3-5mm bio-zeolite(BZ) was not as good as0.1-0.9mm. Therefore, the smaller the particle size, the better the bio-film covered on the NZ.(2) The adsorption kinetics procedure of BZ was similar to NZ. Fitting for the Lagergren pseudo-second-order kinetic model it had the characteristics of fast adsorption (0-2h) and slow balance (2-48h). All of the two procedure could be fitted with the Langmuir adsorption isotherm. The adsorption capacities of0.1-0.9mm NZ.0.1-0.9mm BZ,3-5mm NZ,3-5mm BZ were11.85mg/g,13.4mg/g,9.3mg/g,11.35mg/g. respectively. There was little diffence on adsorption capacity between NZ and BZ with the same particle size. And the bio-film did not inhibit the ammonium adsorbtion on zeolite.(3) Since the PRB was limited by the adsorption ability of river sands and the IM-PRB4was limited by the reduction products of irons-ammonium, both of them had a high effluent concentration of ammonium (>2mg/L). Though the ammonium removal efficiency of M-PRB was more than99%, it presence the adsorption saturation problem of zeolite. Depending of the strong ion exchange adsorption of zeolite, the ammonium removal efficiencies of IM-PRB1, IM-PRB2, and IM-PRB3were higher than99%. And IM-PRB1, IM-PRB2, and IM-PRB3could achieve part of the biological ammonium removal by the denitrification effect, reduce zeolite adsorption loads, and promote the biological regeneration.(4) Compared with M-PRB1, the stronger nitrification effect in IM-PRB2and IM-PRB3was more conducive to the regeneration and longevity of zeolite. However, the cost of ceramsite used in IM-PRB2and IM-PRB3was10times higher than that of zeolite. The savings from operation and maintenance might not be able to compensate the additional expenditure. IM-PRB1would have the highest value of engineering application if every aspects were taken into consideration.