Abstract
The Caspian Sea water is attractive to investigators due to low TDS (less than 15,000 ppm) and possibilities of use low-pressure membranes. But a key problem is that boron is poorly rejected by membranes under pH values below 9. Thus boron content in product water exceeds hygienic standards. Due to relatively high hardness and high boron content, a technological scheme included clarification, acid and antiscalant dosage as pretreatment, double stage RO with caustic dosing into the 1st stage product, product water post treatment. A research program was undertaken to reveal possibilities to reduce capital and operational costs. The investigation included evaluation of ultrafiltration reliability, antiscalant behavior and product water composition prognostic techniques. The paper describes experimental procedures and results that enabled us to determine: an optimum correlation between filtration and backwash duration ensuring best reliability of ultrafiltration pretreatment; RO flow decrease due to CaCO 3/CaSO 4 accumulation and antiscalant efficiency to increase recovery, to increase pH value and better reject boron; optimum recovery limits, product composition and best suitable membrane type.
Published Version
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