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In this study, we investigated the effects of sodium chloride (concentrations ranging from 0 to 60 g/L) on the performance of sequencing batch reactors (SBRs) using a microbial culture developed from a domestic sewage treatment plant. The lab-scale SBRs were fed with synthetic wastewater (acetate as the organic substrate) containing either sodium chloride solution or seawater to ensure consistency in feed composition. It was found that sodium chloride concentrations of up to 10 g/L stimulated substrate removal. The organic removal efficiency decreased from 96%, when no sodium chloride was added, to 86% when 60 g/L of sodium chloride was introduced into the influent wastewater. Effluent turbidity increased significantly when the sodium chloride concentration in the wastewater was equal to or above 30 g/L even though the sludge volume index (SVI) decreased. The increase in effluent turbidity could be caused by the release of nondissolved cellular components due to plasmolysis of microorganisms as observed by scanning electron microscopy. Experiments involving seawater (with 20 g/L total dissolved solids) showed that organic removal efficiency improved from 87 to 95% while effluent turbidity and SVI values were lowered when the loading rate parameter ([L.sub.i]) was lowered from 0.6 to 0.3 mg total chemical oxygen demand (mg VSS day). Optical microscopy and scanning electron microscopy indicated morphological changes in the microbial population. From this study, it was concluded that microbial culture from domestic wastewater facilities could be acclimated in a SBR to treat wastewater containing sodium chloride concentrations of up to 60 g/L. DOI: 10.1061/(ASCE)0733-9372(2005)131:11(1557) CE Database subject headings: Reactors; Dissolved solids; Chloride; Sea water; Sludge; Turbidity.

Performance stability of a biofilm airlift suspension reactor (BASR) was studied using ethanol as a substrate. The main objective of this research was to investigate the applicability of the reactor as a wastewater treatment process by examining the effects of soluble chemical oxygen demand (SCOD) loading rate and hydraulic retention time (HRT) on the performance of the reactor. SCOD removal of 90% or higher was achieved at an HRT of 45 min with loading rates from 10 to 18 kg SCOD/[m.sup.3] day. Similar results were obtained at HRTs of 60 and 90 min and a SCOD loading rate of 10 kg SCOD/[m.sup.3] day. Nitrification occurred in the system when the ratio of SCOD to ammonia nitrogen was changed from 10:1 to 6:1. The morphology of the biofilm in the BASR was denser and thicker when nitrifiers grew in the biofilm. Filamentous overgrowth was observed from time to time and proper chlorine dose successfully suppressed its growth. The oxygen uptake rate was an effective tool for monitoring the effect of chlorination. CE Database subject headings: Biofilm; Cisterns; Wastewater treatment; Nitrification: Chlorination.

Performance stability of a biofilm airlift suspension reactor (BASR) was studied using ethanol as a substrate. The main objective of this research was to investigate the applicability of the reactor as a wastewater treatment process by examining the effects of soluble chemical oxygen demand (SCOD) loading rate and hydraulic retention time (HRT) on the performance of the reactor. SCOD removal of 90% or higher was achieved at an HRT of 45 min with loading rates from 10 to 18 kg SCOD/m[sup 3] day. Similar results were obtained at HRTs of 60 and 90 min and a SCOD loading rate of 10 kg SCOD/m[sup 3] day. Nitrification occurred in the system when the ratio of SCOD to ammonia nitrogen was changed from 10:1 to 6:1. The morphology of the biofilm in the BASR was denser and thicker when nitrifiers grew in the biofilm. Filamentous overgrowth was observed from time to time and proper chlorine dose successfully suppressed its growth. The oxygen uptake rate was an effective tool for monitoring the effect of chlorination. [ABSTRACT FROM AUTHOR]