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On-site greywater recycling is one of the main ways of preserving water resources in urban or arid areas. This study aims to formulate model synthetic greywater (SGW) in order to evaluate and compare the performances of several recycling processes on a reproducible effluent. The formulated SGW is composed of septic effluent to provide indicators of faecal contamination, and technical quality chemical products to simulate organic pollution of greywater. To ensure that the SGW developed is representative of household greywater, its analysis was compared to real greywater collected and analysed (RGWs) and to real greywater mentioned in previous publications (RGW(L)). The performance of a direct nanofiltration process with a concentration factor of 87.5% at 35 bar was then tested on both real greywater and SGW. The laboratory experimental results are promising: fluxes and retention rates were high, and similar for both effluents. The permeation flux was higher than 50 L h(-1) m(-2). Retentions greater than 97% for biochemical oxygen demand for 5 days (BOD5) and 92% for anionic surfactants were observed. No Enterococcus were detected in the two permeates. These results confirm that the model SGW developed in this study shows the same behaviour as real greywater when recycled. Thus, the use of this SGW developed in this study was validated for the evaluation of membrane efficiency to treat greywater. This new tool will be a real asset for future studies.

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Swales are recognized as traditional basic open-drainage systems which are obviously capable to remove stormwater-borne pollutants. In spite of the numerous case studies on their performances, an overall assessment of swale efficiency to reduce pollutant discharge as well as an evaluation of the factors that could influence it are rare. In order to gain a better understanding of these aspects, a database was designed by collecting performance results and design characteristics from various swales reported in the literature. Investigations on correlations amongst pollutant efficiency ratios (ERs) indicated that total trace metals (copper (Cu), zinc (Zn), cadmium (Cd) and lead (Pb)), total suspended solids (TSS), total phosphorus (TP) and total kjeldahl nitrogen (TKN) exhibited many cross-correlated ERs, thus suggesting that they are mainly removed by the same processes in swales. Higher ERs were generally related to pollutants in particulate form, suggested that sedimentation and filtration should be considered as major processes involved in pollutant removal within swales. Furthermore, major discrepancies amongst swale performances may be attributed to variations of site mean inflow concentrations, found as the most recurrent factor influencing ER. Conversely, swale design factors were rather poorly correlated with ER, except swale length, positively correlated with TP and copper.

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