Water recovery from floor cleaning operations of industrial or public areas: The results of a field test

Water resources are increasingly under pressure because of human activities and economic development. Moreover, accelerated urbanization and the expansion of drinking water supply and sanitation systems contribute to this rising demand. The development of water reuse solutions is an urgent issue. This study presents a solution for the reuse of wastewaters generated from floor cleaning operations of industrial or public areas. A portable device containing a grid, for coarse filtration, and a 300-L reaction chamber to carry out the sequential processes of coagulation, flocculation and settling, was employed for a field test. In the field test the wastewater coming from the tank of a cleaning machine, used for floor cleaning in an industrial site, was treated and reused for the same purpose for a total of 110 times. The quality of the treated wastewater was monitored cycle after cycle and the results of the test demonstrated that the treated water was suitable to be reused for the same purpose, even after a large number of cycles, provided that a finishing treatment was eventually supplemented in order to reduce the residual concentration of organic substances. It was demonstrated that, under standard operating conditions, that is a wastewater with a total suspended solid (TSS) content of 800 mg/L, and on the grounds of the results found in the test, that is a TSS removal efficiency of 98% and a sludge total solid (TS) content of 6%, the whole volume of the cleaning machine tank was completely renewed with fresh water after 60 cycles. Eventually, the combination of treatment and reuse operations allowed to save approximately 18,000 L of fresh water over a series of 60 cleaning cycles. The proposed treatment allowed not only to save fresh water but even to reduce the cost of water usage by approximately 50%. In fact, thanks to this treatment, the cost of a single cubic meter of water decreased from approximately 6 €/m3, which included supply of fresh water and discharge to the public sewer, to approximately 3 €/m3.