Recycle Loads Management Strategy Accounts for the Impact of Regional Anaerobic Solids Digestion on Low Limit Biological Nutrient Removal
Abstract:This paper evaluates alternatives investigated to reduce chemical addition at a water reclamation facility with anaerobic digestion recycle streams. The alternatives evaluated were: 1. the MLE process with alum addition for P removal and denitrifying filters for N removal (MLE alternative), and 2. the 5-stage Bardenpho alternative process of biological phosphorus removal, activated sludge biological denitrification using methanol addition and the Ostara struviterecovery recycles treatment process was considered. The 5-stage Bardenpho alternative resulted in annual cost operational savings of 640,000–770,000 compared to MLE alternative under present load conditions and 700,000–800,000 under future load conditions. Reduce chemical and electrical energy consumption and increase net digester methane gas production are other major benifits. The cost of a 5-stage Bardenpho conversion was estimated at 6.1 million. The cost of the Ostara facility was estimated at 5.1 million at present load conditions, with an additional 1.4 million at future load conditions. Process performance would significantly increase: the 14 percent reduction in future average MLSS concentration would reduce the secondary clarifiers load and increase process stability; the effluent total phosphorus concentration would be reduced from about 0.9 mg/L to about 0.4 to 0.5 mg/L; and the nitrate load and load variability of the denitrifying filters would decrease. In addition, since the filters would need to remove only about 1.9 to 3.1 mg/L nitrate under the Bardenpho alternative, compared to about 7.4 to 7.7 mg/L under the MLE alternative, this would significantly reduce the risk of methanol or nitrate effluent breakthrough.
Document Type: Research Article
Publication date: 2009-01-01
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