Cooling Tower Blowdown Water Research Articles

Treatment of cooling tower blowdown water containing silica, calcium and magnesium by electrocoagulation

This research investigated the effectiveness of electrocoagulation using iron and aluminium electrodes for treating cooling tower blowdown (CTB) waters containing dissolved silica (Si(OH)(4)), Ca(2 + ) and Mg(2 + ). The removal of each target species was measured as a function of the coagulant dose in simulated CTB waters with initial pH values of 5, 7, and 9. Experiments were also performed to investigate the effect of antiscaling compounds and coagulation aids on hardness ion removal. Both iron and aluminum electrodes were effective at removing dissolved silica. For coagulant doses < or =3 mM, silica removal was a linear function of the coagulant dose, with 0.4 to 0.5 moles of silica removed per mole of iron or aluminium. Iron electrodes were only 30% as effective at removing Ca(2 + ) and Mg(2 + ) as compared to silica. There was no measurable removal of hardness ions by aluminium electrodes in the absence of organic additives. Phosphonate based antiscaling compounds were uniformly effective at increasing the removal of Ca(2 + ) and Mg(2 + ) by both iron and aluminium electrodes. Cationic and amphoteric polymers used as coagulation aids were also effective at increasing hardness ion removal.

Dow membranes recycle cooling tower blow-down water

Dow Water & Process Solutions, a division of US-based Dow Chemical Co, reports that its dual-membrane technology is helping a power plant in China to reuse blow-down water from its cooling towers.

The cross-flow microfiltration of problematic surface and river waters to produce potable water

Cross-flow microfiltration (CFMF) using a polyester fabric hose support has been successfully used to treat a range of problematic waters. A prototype CFMF unit with a production capacity of up to 200 kl/d has been constructed and operated at a water works to produce water with a lower turbidity than that produced by alum coagulation, settling and filtration. A calcium carbonate precoat was used on the tubes. This has a significant effect on the permeate rate and quality. The process has also been used to treat polluted water to a reverse osmosis feed standard. A silt density index (SDI) of 3.1 was obtained after treating cooling tower blow-down water. Sewage works tertiary effluent was treated in a CFMF unit using a range of precoats. A seven fold increase in permeate flux and an improved permeate quality was obtained through the selection of the correct precoat layer.

A method for chromate removal from cooling tower blowdown water

Efficient removal of soluble Cr(VI) and precipitated Cr(III) has been demonstrated in the laboratory. The process utilizes ferrous ions to reduce the Cr(VI) species and fine magnetite to act as a nucleation and weighting agent. By this means the hydrous metal oxides are removed effectively and rapidly from suspension. The adsorbed metal flocs may be removed from the magnetite by mechanical or chemical means to allow reuse of the magnetite. This process for the removal of chromate could be competitive with the existing ferrous sulfate reduction-flocculation and ion-exchange processes.