DEVELOPMENT OF CLOSED-LOOP WATER REUSE / SYSTEM FOR LARGE WIRE EXTRUSION FACILITY
In developing this problematic permit, the state regulatory agency issued stringent NPDES limits for this large cable manufacturer. The permit included limits for metals at part per billion (ppb) levels and low effluent biochemical oxygen demand (BOD) based on categorical effluent limits.
The permit also required an unspecified reduction in discharge volume via treatment or other appropriate technologies. Advanced treatment techniques were required to reduce effluent metals concentrations to meet the proposed Water Quality Based Effluent Limitations (WQBEL's).
metals loadings resulted from dissolution of metals contained in dyes in extruded plastic and rubber compounds. Source water was from the receiving stream upstream of the facility. Up to one million gallons per day (mgd) was used in contact and non-contact cooling water processes.
an alternatives evaluation, undertaken to assess treatment and facility upgrades to meet NPDES permit limits, the choice was made by the facility to implement an effluent recycle / ‘near closed-loop’ process. Design was completed in 2001 and construction in early 2002.
aspects of this upgrade included:
A complete capture of a myriad of small and large contact and non-contact cooling water sources in a facility performing cable manufacture for 30 years,
to a large roof-mounted cooling tower and chiller,
Sizable energy savings resulting from heat recovery from large volume hot water extrusion baths,
Energy efficient pumps and the use of variable frequency drives
Elimination of both the river source water withdrawal and NPDES discharge,
Water treatment through innovative disinfection using plant processes to disinfect recirculating water at no additional capital costs,
Improvement in product quality resulting from use of a high quality, chlorinated municipal feed for makeup water,
Measurable increases resulting from increased capacity in product cooling, and
maintenance reduction with elimination of water supply infrastructure.
The cooling system has been operational since March 2002. Prior to construction, water use (withdrawal and discharge) averaged approximately 0.8 mgd with peaks as high as 1.0 mgd. Post-construction
makeup water demand has averaged approximately 40,000 gpd and POTW discharge 4,000 gpd resulting in a 20:1 recirculating / reuse ratio.
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