Pool filter backwash accounts for a significant share of wastewater generated in swimming pool facilities. Although rinsing water is taken from the expansion tank, it is necessary to replenish water loss on a regular basis. For example, the daily water consumption of a recreational swimming pool and a hydromassage tub with a total capacity of the water treatment system of 75.9m3/h is 9.88m3/d. The rising costs of water intake, wastewater discharge, and water scarcity necessitates that swimming pools seek solutions that would reduce the facility maintenance costs.
One of the options of limiting wastewater discharge is to recycle backwash. The main problem with this is the high content of suspended solids and elevated concentration of chlorine compounds in the backwash. Therefore, before it is discharged into the environment, it is necessary to conduct pre-treatment, in particular, sedimentation and dechlorination. In addition to compliance with the physicochemical standards, it is also necessary to take into account the ecotoxicological impact of wastewater discharge.
The presented studies have analysed the physicochemical and phytotoxicological parameters of backwash from two swimming pools. Ten independent samples were taken from each pool being tested in order to measure several chosen indicators and conduct bioassays using Lepidium sativum, Sinapis alba, and Lemna minor. The influence of dilution and the matrix of diluted backwash were also analysed. Solutions with 0, 5, 10, 25, 50, 75, and 100% of backwash diluted with deionised water, tap water, or rainwater were prepared and the influence of dilution on the obtained responses from plant indicators was determined. The objective of the study was to identify whether it might be possible to use backwash after pre-treatment for the purpose of irrigation.