Natural diatomite mediated continuous anaerobic sludge digestion: Performance, modelling and mechanisms

The extent of reduction in selected microorganisms was tested during both aerobic wastewater treatment and anaerobic digestion of sludge at the wastewater treatment plant in Ottawa to compare the removal of two encysted pathogenic protozoa with that of microbial indicators. Samples collected included the raw wastewater, the primary effluent, the treated wastewater, the mixed sludge, the decanted liquor, and the cake. All of the raw sewage samples were positive for Cryptosporidium oocysts and Giardia cysts, as well as for the other microorganisms tested. During aerobic wastewater treatment (excluding the anaerobic sludge digestion), Cryptosporidium and Giardia were reduced by 2.96 log10and 1.40 log10, respectively. Clostridium perfringens spores, Clostridium perfringens total counts, somatic coliphages, and heterotrophic bacteria were reduced by approximately 0.89 log10, 0.96 log10, 1.58 log10, and 2.02 log10, respectively. All of the other microorganisms were reduced by at least 3.53 log10. Sludge samples from the plant were found to contain variable densities of microorganisms. Variability in microbial concentrations was sometimes great between samples, stressing the importance of collecting a large number of samples over a long period of time. In all cases, the bacterial concentrations in the cake (dewatered biosolids) samples were high even if reductions in numbers were observed with some bacteria. During anaerobic sludge digestion, no statistically significant reduction was observed for Clostridium perfringens, Enterococcus sp., Cryptosporidium oocysts, and Giardia cysts. A 1-2 log10reduction was observed with fecal coliforms and heterotrophic bacteria. However, the method utilized to detect the protozoan parasites does not differentiate between viable and nonviable organisms. On the other hand, total coliforms and somatic coliphages were reduced by 0.35 log10and 0.09 log10, respectively. These results demonstrate the relative persistence of the protozoa in sewage sludge during wastewater treatment.Key words: Cryptosporidium, Giardia, indicators, wastewater, sludge.

Download Full-text

SURVIVAL OF ENTEROVIRUSES DURING ANAEROBIC SLUDGE DIGESTION

Advances in Water Pollution Research ◽

10.1016/b978-0-08-017005-3.50016-5 ◽

1973 ◽

pp. 99-107 ◽

Cited By ~ 2

Author(s):

A. PALFI

Keyword(s):

Anaerobic Sludge ◽

Sludge Digestion ◽

Anaerobic Sludge Digestion

Download Full-text

Enhancement of performance and biodegradability kinetics of aerobic-anaerobic sludge digestion

E3S Web of Conferences ◽

10.1051/e3sconf/202016701010 ◽

2020 ◽

Vol 167 ◽

pp. 01010 ◽

Cited By ~ 1

Author(s):

Boonchai Wichitsathian ◽

Jareeya Yimratanabovorn ◽

Watcharapol Wonglertarak

Keyword(s):

Organic Matter ◽

Removal Efficiency ◽

Aeration Rate ◽

Anaerobic Sludge ◽

Sludge Reduction ◽

Excess Sludge ◽

Sludge Digestion ◽

Anaerobic Sludge Digestion ◽

Aerobic Sludge ◽

Biodegradable Organic Matter

The excess sludge problem from a wastewater treatment plant is a great concerned due to the high cost of sludge management accounting for about 20% to 50% of the total operating cost. Therefore, sludge reduction is critical. Currently, aerobic and/or anaerobic sludge digestions are widely used in the industries for treating the excess sludge. The objective of this research was to study the effects of aeration rate and temperature on the excess sludge reduction by using the aerobic-anaerobic digestion system in the laboratory. The aeration rates of 1.0, 0.5, and 0.1 volume air per volume slurry per minute (vvm) at the room temperature and the thermophilic temperature (55 ± 2°C) were investigated. The results showed that the highest removal efficiency of aerobic sludge digestion was obtained at the thermophilic temperature and aeration rate of 1.0 vvm. The removal efficiency of organic matter in terms of COD, total solids (TS) and volatile solids (VS) were 34.76%, 33.01% and 43.45%, respectively. Consequently, the highest specific growth rate of microorganisms was 0.39 per hour and the substrate removal rate was 0.55 milligram CODremoved per milligram VSS per hour. Furthermore, slowly biodegradable organic matter was hydrolyzed to readily biodegradable organic matter and inert soluble organic matter. When the sludge effluent from aerobic sludge digestion was feed to the anaerobic sludge digestion, the removal efficiency of organic matter in terms of COD, TS and VS were increased by 25%, 17% and 28%, respectively. Moreover, the obtained methane production rate in the anaerobic sludge digestion was approximate 0.234 m3/kg COD removed.

Download Full-text

Sludge digestion enhancement and nutrient removal from anaerobic supernatant by Mg(OH)2 application

Water Science & Technology ◽

10.2166/wst.2001.0039 ◽

2001 ◽

Vol 44 (1) ◽

pp. 161-166 ◽

Cited By ~ 20

Author(s):

Q. Wu ◽

P. L. Bishop ◽

T. C. Keener ◽

J. Stallard ◽

L. Stile

Keyword(s):

Biogas Production ◽

Treatment Plant ◽

Pilot Scale ◽

Ammonia Nitrogen ◽

Phosphate Removal ◽

Anaerobic Sludge ◽

Phosphorus Concentration ◽

Sludge Stabilization ◽

Sludge Digestion ◽

Anaerobic Sludge Digestion

Anaerobic sludge digestion is a widely adopted process for sludge stabilization. Phosphate removal from anaerobic supernatant is necessary to limit the phosphate returned to the head of the treatment plant, thereby improving the overall treatment efficiency. In this study, magnesium hydroxide (Mg(OH)2) was used to improve the sludge digestion efficiency and to remove phosphorus from anaerobic supernatant. The anaerobic sludge digestion experiment was conducted at a pilot scale, and the results showed that applying Mg(OH)2 to anaerobic sludge digester resulted in a larger reduction in SS and COD, a higher biogas production rate, a lower level of phosphate and ammonia nitrogen concentrations in the sludge supernatant and an improved sludge dewaterability. Research results at both lab scale and pilot scale on phosphorus removal from anaerobic supernatant using Mg(OH)2 showed that a high removal of phosphorus can be achieved through the addition of Mg(OH)2. The required reaction time depends on the initial phosphorus concentration and the Mg(OH)2 dosage.

Download Full-text