Removal of non-biodegradable compounds from stabilized leachate using VSEPRO membrane filtration

In this paper, the technical applicability of the vibratory shear-enhanced processing reverse osmosis (VSEPRO) membrane system for the treatment of stabilized leachate from the NENT landfill in Hong Kong was studied using both 99 and 96% NaCl rejection membranes. The performance of VSEPRO for NH3-N and COD removal was evaluated and compared to the performances of other individual and/or combined treatments from other studies. Without any pH adjustment, it was found that the rejection rates of VSEPRO were 96% for COD and 98% for NH3-N with initial COD and/or NH3-N concentrations of 8000 and 2620 mg/L, respectively. It was evident that pH adjustment of raw leachate to acidic conditions (pH 6.0) slightly improved the rejection rates for COD (97%) and NH3-N (99.6%). These results were satisfactory compared to other physicochemical treatments. It is important to note that the treatment of leachate using VSEPRO was able to meet the local effluent limit for COD of lower than 200 mg/L and for NH3-N of less than 5 mg/L. This result suggests that VSEPRO is technically applicable and appealing for the treatment of stabilized leachate.

3.4. Comparison of removal performance with other physicochemical techniques for leachate treatment To evaluate the performances of different treatments investigated in the present study, a comparative study is presented in terms of pH, dose required (g/L) and initial concentration of COD and NH3-N (mg/L) in the leachate. Table 6 summarizes the COD and/or NH3-N removal efficiency of various individual and/or combined treatments in previous studies. Although it has a relative meaning due to the different testing conditions such as pH, temperature, the strength of wastewater, seasonal climate and hydrology site, this comparison is useful to evaluate the overall treatment performance of each technique for a decision-making process. Struvite precipitation has achieved 98% treatment efficiency for NH3-N removal with an initial concentration of 7511mg/L. An outstanding COD removal of 96–98% has also been demonstrated by nanofiltration (NF) and reverse osmosis (RO) with COD concentrations ranging from 3840– 17,000 mg/L. Among the various combined treatments, the combination of RO and UASB (with initial COD and NH3-N concentrations of 35,000 and 1600 mg/L, respectively) has achieved an almost complete removal of COD and NH3-N. When compared to the treatment efficiencies presented in Table 6, the removal of COD (97%) and/or NH3-N (99.6%) by VSEPRO treatment (with pH adjustment) in this study is very satisfactory. Moreover, the total COD and NH3-N removal in this study was higher (COD: 97% out of 8000 mg/L; NH3-N: 99.6% out of 2620 mg/L) It is evident from the study that the use of VSEPRO for the removal of COD and/or NH3-N from landfill leachate is technically applicable and appealing. The advantages of using this membrane system for the treatment of leachate are the simplicity of the treatment and its ability to treat stabilized landfill leachate of varying strengths and compositions. Without any pH adjustment, it was found that the rejection rates of VSEPRO were 96% for COD and 98% for NH3-N with initial COD and/or NH3-N concentrations of 8000 and 2620 mg/L, respectively. pH adjustment of the raw leachate to acidic conditions (pH 6.0) did not significantly improve the rejection rates for COD (97%) and NH3-N (99.6%). These results were very satisfactory compared to those of other physicochemical treatments. It is important to note that the treatment of leachate using VSEPRO could meet the local effluent limit for COD of lower than 200 mg/L and for NH3-N of less than 5 mg/L. This result suggests that VSEPRO is technically applicable and appealing for the treatment of stabilized leachate. No biological process is required for further treatment of the leachate, thus reducing operational costs.