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Chemical and Process Engineering Resources

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Category: Plant Economics
Question: What factors should be included in evaluating the costs associated with precipitating metals from aqueous waste streams?
Keywords: costs,precipitating,precipation,metals,aqueous,waste,streams
Answer: The following factors should be considered:Type of metal and concentration level   Precipitation is often effective from levels from 1 to 1,000 mg/L. Multiple metals may need to be treated as well. Both metal type and the concentrations of each metal are used to determine the feed rate and the rate of sludge generation.
Flowrate   Flowrate is used to determine the size of the treatment equipment that will be necessary. Typical flowrate are from 350 to 1,000 gallons per minute for a process stream and up to 125 gallons per minute for groundwater treatment.
Influent pH   If pH adjustments of more than one are necessary, this may necessitate the purchase of additional equipment. You should always assume that a pH adjustment of at least one will be necessary. pH adjustments may be determined based on the precipitation agent choosen and the amount of the agent needed.
Effluent pH   If pH adjustment before discharge will be necessary (typically a discharge pH range of 6-8 is allowed), additional equipment may be necessary to neutralize the outgoing stream.
Treatment Duration   Treatment duration should be factored into equipment sizing and total throughput.
Worker Safety   OSHA 29CFR Part 1910 includes four levels of safety (A,B,C, and D). "A" is the highest level of safety and "D" is the lowest level. Increased safety levels will increase equipment costs and labor rates.
Links: OSHA 29CFR Part 1910