Wastewater treatment alternatives for a vegetable and seafood cannery
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Peeled or whole-pack tomatoes, herring roe and oysters are processed at a Virginia Cannery. Wastewater from each food processing effluent was characterized. Treatment alternatives were investigated for tomato and herring roe wastewaters. For herring roe processing wastewater, the discharge requirement for BOD was nearly met through plain settling, while the TSS limitation was easily achieved by settling out the roe particles" Oyster processing wastewater was found to meet effluent guidelines without treatment.
Bench-scale treatability studies were performed using sequencing batch reactors (SBRs) to treat the segregated wastewater from the caustic tomato peeling operation. This isolated 98% of sodium present in the wastewater.
Previously, all wastewater was land applied and the high sodium content damaged soil structure. Sodium levels in monitoring wells below the irrigation field have risen, approaching regulated values. Results indicated that SBRs can be effective in reducing BOD and TSS to discharge requirements. BOD and TSS removals were well in excess of 90%. Initial values for BOD and TSS were 21,400 mg/l and 14,000 mg/l, respectively. Although conventional food to microorganism ratios were used, relatively long hydraulic retention times of 8 to 20 days were required to accomplish adequate BOD removal. Screening was found to be an effective form of pretreatment to remove large quantities of TSS.
It appears practical to treat the tomato peeling wastewater by means of sludge drying beds. Approximately 0.5 acre of land would be required for bed construction. Final disposal costs associated with landfilling the dried sludge may govern whether sludge drying beds or an SBR should be used. In an effort to eliminate wastewater problems associated with the caustic peeling operation, an enzyme peeling study was performed using pectinase. Peeling ability of the enzyme was not as good as that of caustic, however, further investigation into alternative peeling operations is warranted due to the adverse effects of caustic materials on wastewater treatment alternatives.
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