How additives affect microbial populations and overall breakdown of municipal waste in anaerobic digesters

Date

1998-05

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Journal ISSN

Volume Title

Publisher

Texas Tech University

Abstract

A bench scale analysis of twelve 4-Liter anaerobic digesters with a 3-Liter working volume were operated to examine the effects of five commercial additives on the degradation of primary municipal sludge. The reactors were loaded with 150 ml per day of 3% volatile-solid content waste collected from the Lubbock Municipal Treatment Plant. Ten of the reactors were loaded with one of five commercial additives, in duplicate, with two reactors serving as the control. The objective of the experiments was to determine the efiects that the additives would have on the performance of the digestion of the waste and the microbial populations. It was found that during steady state operation, the total volatile solids content of reactors with the Biocope additive were significantly lower (16.5%) than the control (p<0.05), for an overall increase in volatile solids degradation of 8.2%. A preliminary levelone economic feasibility test showed that $193,257 could be saved over an assumed 20 years of operation, by constructing an 8.2% down-sized treatment plant with the inclusion of Biocope^^, based on an average flow rate of 1 million gallons per day of wastewater into the treatment plant. During the last two and one-half months of operation, pH, and anaerobic bacteria levels were substantially lower (p<0.05) in reactors loaded with the MPC additive than the control reactors. The total volatile solids destruction and chemical oxygen demand removal, and biomass readout from the HMBrV device were also was significantly lower (p<0.05) in these reactors than in the control.

The HMB-IV device used to measure aerobic activity of a sample, was shown to be effective in determining unsteady mixing in the anaerobic digesters, and early detection of a drop in pH below the threshold value of 6.5. HMB-IV readings significantly dropped 1-2 weeks before a pH drop would be detected that would inhibit the digestion process. It was concluded that the HMB-IV device could be excellent for early detection of process failure thereby providing an early response to corrective action.

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Keywords

Anaerobic bacteria, Digestion, Sewage sludge digestion

Citation