A municipal wastewater plant (WWP) has biosolids with a zinc concentration above the biosolids criterion for zinc. The WWP found zinc concentrations in sediments contained in a fruit packing plant that discharges its wastewater for treatment. The plant's wastewater settling pit sediments measured at 1500mg/Kg. A water analysis yielded 162 ug/L. Another set of analysis of pit samples found 71.5 mg/L in a liquid/soild sample. The plant swears they do not use zinc containing chemicals at the packing house.

Are there any zinc containing compounds that are used in the orchards or packing house that the packing house would not be aware of. The high zinc levels in the biosolids are costly to dispose of at a landfill.

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