Treatment of Laundry Wastewater by Physicochemical and Flotation Processes

Abstract

AbstractLaboratory and field studies were conducted to evaluate the capabilities of two commercially available laundromat waste treatment systems to treat laundromat wastes with the possibility of recycling the treated effluent: (a) The Winfair Water Reclamation System (WWRS) involves the addition of alum to a pH of 4, sedimentation, sand filtration, carbon absorption, and passage through ion exchange resins and (b) The American Laundry Machinery Industries (ALMI) system employs chemical precipitation prior to filtration through diatomaceous earth. Lenox Institute of Water Technology (LIWT) designed a physicochemical process system involving mainly the use of dissolved air flotation (DAF) for treating the same laundry wastewater.The WWRS achieved a 56% BOD reduction, 62% COD reduction, and 94% ABS reduction, but suffered from a buildup of total solids in the effluent. The system produced an effluent suitable for discharge into many streams. For effluent recycling, a functioning demineralizer would be required.The ALMI system achieved a 63% BOD reduction, 69% COD reduction, 87% ABS reduction, 94% P04 reduction, and complete coliform removal. The increase in effluent alkalinity and hardness render very questionable the suitability of the effluent for reuse without softening and pH adjustment.A LIWT system has been specifically designed for small operations, such as small laundromats, prewash laundries, car washers, although large laundry plants may also adopt. It is a rectangular DAF-sedimentation system without moving parts. According to the investigation of the US Environmental Protection Agency (USEPA), a DAF unit can: (a) remove 50% COD, 59% TOC, 75% TSS, 80% O&G, and 96% TP from a laundry wastewater, if 1800 mg/L calcium chloride and 2 mg/L of polymer are dosed or (b) remove only 8% COD, 38% TOC, 36% TSS, 59% O&G, and 9% TP from a laundry wastewater, if only 60 mg/L polymer is dosed. Many heavy metals and organic pollutants may also be removed by DAF at the same time. There are over thousands of commercial Supracell DAF and Sandfloat DAFF, and KAMET-DAF-DAFF systems installed and operated for treating various industrial wastewaters around the world. They (Supracell, Sandfloat, and KAMET) are suitable for use by large auto and laundry industries, but may not be suitable to small laundromats because there are many moving parts. Other commercial DAF units, such as Clari-DAF and AquaDAF, have been applied to only drinking water treatment. It is the authors’ professional judgment that either Clari-DAF or AquaDAF should be able to adequately treat the wastewater from a laundry plant, if adequate chemicals are used. A consulting engineer has successfully treated a prewash laundry wastewater using DAF. Construction of the LIWT rectangular DAF-sedimentation plant for treatment of laundry and car wash wastewaters using the optimized chemicals is recommended. This laundry wastewater treatment research was started by late Dr. Donald B. Aulenbach. Researchers around the world are invited to continue his research in order to find the best solution to treating the large-scale auto and laundry wastewater, and the small laundromat, prewash laundry, and car wash wastewaters. This was Dr. Aulenbach’s final wish conveyed to his coauthors in 2019.KeywordsWinfair Water Reclamation System (WWRS)American Laundry Machinery Industries System (ALMI)InnovationLenox Institute of Water Technology Wastewater Treatment System (LIWT)Dissolved air flotationSupracellDAFSandfloatDAFFKAMETDAF-DAFFClari-DAFAquaDAFPretreatmentMunicipal sewer dischargeRectangular DAF-sedimentation systemCar wash wastewater treatmentPrewash laundry wastewaterUSEPA investigations