Municipal Wastewater Treatment by USAB Process: Start-up at 20°c and Operation at Low Temperatures

Abstract

Laboratory-scale UASB reactors were started-up successfully at 20 degrees C and operated at temperatures of 32, 20, 15, 11, and 6 degrees C applying several hydraulic retention times (HRTs) ranging from 48 to 3 h during an operational period of approximately 900 days. Changes in temperature and HRTs impacted the reactor performance. However, overall reactor performance (70 to 90% COD removal) was found to be stable up to an HRT of 6 h and temperature of 11 degrees C. The performance of UASB reactor was not very stable during 6 degrees C operation, even though 30 to 50% of COD removal could be achieved. Biomass aggregation in the form of granules/bio-pellets (mean size ranged from 1.8 mm to 3.0 mm) could be achieved during 20 degrees C operation. The impact of temperature on morphology, surface structure, and shape of bio-pellets was explored. Morphological and elemental composition analyses showed the possible mechanism of biomass aggregation in UASB reactors. This study demonstrated that the UASB process could be applied successfully with some minor adjustment for the treatment of municipal wastewater in temperate and cold regions (average summer temperature 11-25 degrees C).

Anaerobic treatment of a medium strength industrial wastewater at low-temperature and short hydraulic retention time: a pilot-scale experience

“…The percentage of methane for T3 was estimated using the average of Tl and T2. Singh & Viraraghavan (2004) attributed their low methane production to a high fraction of particulate COD in the influent, the low operation temperature and the COD consumed during sulfate reduction; however, in our investigation, only the low operation temperature and the biogas losses due to biogas pocket release may have affected the low measured SMP. These values were low compared with the standard SMP (0.35 m^ CH4/kg CODsoi-removcd) (Metcalf & Eddy, Inc. 2003), but they were in the same order of magnitude achieved by others (Torkian et al 2003;Singh & Viraraghavan 2004;Akila & Chandra 2006).…”

“…Figure 2(b) illustrates the evolution of effluent VFA (as acetic acid) during the entire experiment. Singh & Viraraghavan (2004) noted that the effluent VFA slightly increased after reducing the HRT for different temperatures. During Tl, the effluent VFA was low (41 mg/L) and gradually increased to 84 and 114 mg/L during T2 and T3, respectively, as the influent CODsoi and OLRappi increased.…”

“…Biogas production is considered as an indicator of the stability of anaerobic processes; biogas production usually increases as the HRT decreases and it decreases as the operational temperature decreases (Singh & Viraraghavan 2004). Figure 2(a) illustrates that the correlation between OLRrem and measured biogas production for the three experiments was not representative (R^ = 0.5839), although Hernández-Torres et al (2008) reported a strong correlation (R^ = 0.9197) during previous experiments on the same UASB reactor evaluating similar OLRappi, but longer HRT (6 h).…”

Cold-loving microbes, plants, and animals—fundamental and applied aspects

“…Upward-flow anaerobic sludge blanket reactors gave a stable performance (70-90% COD removal) at an operation temperature of 11°C. At 6°C, COD removal was still 30-50% (Singh and Viraraghavan 2004). Bacteria and fungi that degrade high amounts of organic compounds within a short time at temperatures down to 1°C represent a promising source as inocula for accelerated wastewater treatment and also for the construction of biosensors for the rapid monitoring or in situ analysis of pollution (Alkasrawi et al 1999;.…”

Treatment of tannery wastewater using hybrid upflow anaerobic sludge blanket reactor

“…During the tanning process, a huge volume of wastewater is generated and in most cases it is released into water bodies and agricultural fields with or without treatment. Among the high rate anaerobic reactor designs, the upflow anaerobic sludge blanket (UASB) (Lettinga et al 1980;Fang et al 1990; Lettinga and Hulshoff Pol 1991;Singh andVirarahavan 2004 andLew et al 2004) and anaerobic filter (AF) (Suidan et al 1983;Young andYoung 1991 andSafferman et al 2004) have been successfully commercialized and numerous full-scale systems have been installed worldwide. methane as a by-product of the treatment.…”