Pretreatment and Reuse of Wastewater at Industrial Laundries

摘要

This paper will review the industrial laundries wastewater treatment options and present data from a case study involving the treatability studies and full-scale operating plant. California Linen Rental Company (Laundry) in Oakland, California, supplies laundered linens, clothing, and other washable items to small businesses in San Francisco Bay Area. Laundry installed a wastewater pretreatment and clarification system in order to comply with the East Bay Municipal Utility Distinct (EBMUD) fat-oil-grease (FOG) discharge limits. The pilot-scale demonstration tests proved that the method of magnesium coagulation at pH levels between 11.0-11.5 and anionic polymer flocculation was the best chemical treatment method for the dissolved air flotation (DAF) clarification of the treated wastewater. A multi-media filtration unit was also used after DAF to improve the FOG and total suspended solids (TSS) removal efficiencies. Magnesium chloride addition at 140-200 mg/L as Mg and 4-6 mg/L polymer addition made possible to reduce FOG by 98% and TSS by 85% using a DAF and filtration clarification system. Laundry recycles up to 50% of its treated effluent after reducing FOG, hardness, and TSS in the effluent. Warm treated wastewater is recycled back to the hot water system, saving energy and up to 11 million gal of water per year.