Coliform concentration reduction and related performance evaluation of a down-flow anaerobic fixed bed reactor treating low-strength saline wastewater

Abstract

Low-strength saline wastewater may be generated by tourist facilities, industries and communities located in coastal areas. Sea salts, mostly chlorides, when present in wastewaters at high concentrations, can cause inhibition on biological treatment processes. In this study, a laboratory down-flow anaerobic fixed bed reactor (DFAFBR) was used for treating saline wastewater. This wastewater was simulated by dilution of piggery manure in a synthetic saline water to obtain a final total COD concentration in the range of 1100-2900 mg/l and a salt concentration of 15 g/l. The DFAFBR was operated at hydraulic retention times (HRT) of 96, 48, 24 and 12 h. The results showed that at sea salts concentrations in the range from 5 to 15 g/l, total coliform concentration reduction efficiencies higher than 97% were achieved. A decrease in the total and faecal coliform concentration reduction efficiencies from 99.5% to 90.5% and 92.5%, respectively, was observed when the HRT decreased from 96 to 12 h. Enumeration of coliform bacteria isolated from the biofilm in different zones of the reactor showed that more than 94% of the total amount was removed in the upper zone. A HRT of 24 h was required to obtain total COD, organic-N, total-P and faecal coliform concentration reduction efficiencies higher than 72%, 51%, 39% and 98%, respectively. A concentration of 8.4 g/l for chlorides, 1.25 g/l for sulphates and 4.6 g/l for sodium did not affect the process performance.

Effect of fluctuations in salinity on anaerobic biomass and production of soluble microbial products (SMPs)

“…Debaere et al (1984) found no sodium inhibition up to 29.01 gNa + l -1 , and only at 37.4 gNa + l -1 did the methanogenic activity decrease to 50%. Rovirosa et al (2004) studied the performance of a downflow anaerobic fixed bed reactor treating saline (15 gNaCl l -1 ) synthetic domestic wastewater. Start up lasted 335 days by gradually increasing the NaCl from 5 to 15 g l -1 so the bacteria could acclimatise.…”

Batch treatment of saline wastewater by Halanaerobium lacusrosei in an anaerobic packed bed reactor

“…Rovirosa et al studied the treatment of saline wastewater using a laboratory down-flow anaerobic fixed bed reactor (DFAFBR). 12 The results showed that at sea salts concentrations 5-15 g L −1 , a hydraulic retention time of 24 h was required to obtain better than 72% COD reduction for COD 0 = 1100-2900 mg L −1 . Kapdan and Erten reported over 70% COD removal at 3000 mg L −1 initial COD concentration, 19 h hydraulic retention time, and 3% salt concentration by H. lacusrosei in a continuously operated anaerobic packed bed reactor.…”

The isolation, identification , physiological and biochemical properties of salt-tolerant strains

“…The screened 8 strains were screened, detection their biological growth in the salinity of 5%, 9%, 15% and 18% [5,6,7,8] , determine their respective salt resistance and screen out superiority strains.…”