Impact of high chloride wastewater on an anaerobic/anoxic/aerobic process with and without inoculation of chloride acclimated seeds

The performance of an anaerobic/anoxic/aerobic (2+2+12 h of hydraulic retention time) process with and without inoculation of sodium chloride acclimated seeds was investigated using a synthetic wastewater with COD, nitrogen, and phosphorus of 500, 25, and 15 mg/l, respectively. The sodium chloride in the fed wastewaters varied from 0 (control) to 30 g/l while maintaining the solids retention time at 10 d. The results indicated that the organic (in terms of COD) and nitrogen removal efficiency of the non-acclimated system was reduced from 97 to 60% and 88 to 68% a the salt content increased from 0 to 30 g/l NaCl, respectively, whereas it decreased from 90 to 71% and from 85 to 70% as the salt content rose from 5 to 30 g/l NaCl, respectively, in the salt acclimated system. The phosphorus removal in this study was not as high as those reported elsewhere; probably due to the intense sensitivity of poly-P bacteria to high salt concentration. Time required to reach steady state was higher (10–20 d) for the non-acclimated system than that with acclimation (8–15 d). In addition, it is apparent that the system started up with high salt content and acclimated seed could better tolerate a shock of 70 g/l NaCl as well as required less recuperation period than that initially fed with low salinity and without acclimation.