Wastewater Additives

Project 1

Effect of Additives on volatile Fatty Acid Producation in Anaerobic Digestion

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Abstract :

                Laboratory-scale experiments were conducted to study the effect of additives on the process of anaerobic digestion in general and on the production of volatile fatty acids in particular. Twelve reactors with a working volume of 3-litres were operated as anaerobic digesters and were loaded daily with 150 ml of the primary sludge with an average volatile solids content of about 3%. Five commercial additives - Biocope, Medina d-part, MPC, Alken Clear Flo 4100 and Biosep - were added in duplicates to the total ten reactors and two reactors were operated as control. The influent and effluent from each reactor were analyzed for total volatile solids, volatile fatty acids and pH. The volatile fatty acids were analyzed by using gas chromatography. The addition of Biocope resulted in the greatest reduction of the volatile solids of 47.5%. This was 8.1% greater (P< 0.05) than the reduction of volatile solids in control reactors, which did not receive any additives. Acetic and propionic acids were the only major acids present in the reactors receiving Biocope and Medina d-part. The reactors receiving MPC, Alken Clear Flo 4100 and Biosep produced considerable amounts of six major fatty acids. The reactors receiving MPC developed unbalanced conditions and hence resulted in the lowest destruction in volatile solids and highest concentrations of volatile fatty acids. It was found that only Biocope affected the anaerobic digestion process in a significant manner by causing the highest destruction in volatile solids. A cost analysis performed for a wastewater treatment plant using Biocope as an additive gave a benefit to cost ratio of 2.27, indicating the potential economic advantages associated with its use.

Project 2

How Additives Affect Microbial Populations And Overall Breakdown Of Municipal Waste In Anaerobic Digesters

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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 effects 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 Biocopeä 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 level-one 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 Biocopeä, 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 HMB-IV 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.