Recycling of hospital laundry wastewater using membrane technology

Abstract

The laundry wastewater from a Qatari hospital has been characterized and its membrane filtration behavior studied. 1,800-2,500 L or wastewater per cycle for washing a laundry load of 40-50 kg was determined, with the wastewater shown to be sufficiently polluted to require treatment prior to discharge. Two treatment approaches were adopted, the first being a single membrane technology employing a “tight” ultrafiltration (UF) membrane of 5 kDa molecular weight cut-off (MWCO) and the second a combination of coarser UF of 75 kDa MWCO followed by a nominally 200 Da nanofiltration (NF) membrane. Both approaches were found to be acceptable in terms of pollutant rejection (more than 87%), with the statutory wastewater discharge limit being met. Fluxes of (29-42, 72-100 and 27-54 LMH were determined for the 5 kDa UF the 75 kDa UF and UF-pretreated NF). However, only the dual technology (combination of UF-NF) was able to remove the dissolved solids as evident by the reduction in wastewater conductivity. Results demonstrated that the hospital wastewater can be successfully treated at a pressure of 2.5 bar, temperature 25°C and a crossflow rate of 1 L/min, with rejection and flux being sensitive only to temperature within the range of 25°C-45°C.