# Preliminary Study on Greywater Treatment Using Nonwoven Textile Filters
## 3 Results
### Efficiency of Organic Compounds and Nutrients Removal  
The treatment efficiencies of COD\({}_{\rm Cr}\) of set I and set II were shown in Figure 2.  
The inflow COD\({}_{\rm Cr}\) values were: 227.8 \(\pm\) 26.7 mg dm\({}^{-3}\) (\(n\) = 18) and 153.1 \(\pm\) 9.5 mg dm\({}^{-3}\) (\(n\) = 7) for set I and set II, respectively (Figures 3 and 4). Figure 2: Chemical oxygen demand (COD\({}_{\rm Cr}\)) removal efficiency in set I (**a**) and set II (**b**) during the experiment. Efficiencies of removal of dissolved organic substances expressed as \(\mathrm{COD_{Cr}}\) were: \(68.7\pm 5.6\%\) (\(n=17\)) for filter 1 and \(68.9\pm 4.0\%\) (\(n=18\)) for filter 2 of set I (Figure 3). Efficiencies of \(\mathrm{COD_{Cr}}\) removal by filters of set II were from \(58.8\pm 3.6\%\) (\(n=5\)) to \(71.6\pm 6.4\%\) (\(n=5\)) and were related to their hydraulic capacity (Figure 4). In general--the lower hydraulic capacity--the higher the removal efficiency. The outflow \(\mathrm{COD_{Cr}}\) values were in the range between \(11.0\) mg \(\mathrm{O_{2}}\) dm\({}^{-3}\) and \(124.0\) mg \(\mathrm{O_{2}}\) dm\({}^{-3}\) in the case of set I and between \(19.0\) mg \(\mathrm{O_{2}}\) dm\({}^{-3}\) and \(88.0\) mg \(\mathrm{O_{2}}\) dm\({}^{-3}\) in the case of set II. The results of BOD\({}_{5}\) removal efficiencies of set I and set II were presented in Figure 5.  
Figure 4: Chemical oxygen demand (\(\mathrm{COD_{Cr}}\)) inflow and outflow concentrations (**a**) and removal efficiencies (**b**) for set II. Figure 5: Biochemical oxygen demand (\(\mathrm{BOD_{5}}\)) removal efficiency in set I (**a**) and set II (**b**) during the experiment. Figure 3: Chemical oxygen demand (\(\mathrm{COD_{Cr}}\)) inflow and outflow concentrations (**a**) and removal efficiencies (**b**) for set I. The inflow BOD\({}_{5}\) values were: 70.6 \(\pm\) 5.1 mg dm\({}^{-3}\) (\(n\) = 17) and 49.2 \(\pm\) 4.6 mg dm\({}^{-3}\) (\(n\) = 6) for set I and set II, respectively (Figures 6 and 7). Efficiencies of removal of dissolved organic substances expressed as BOD\({}_{5}\) were: 79.8 \(\pm\) 6.2% (\(n\) = 15) in filter 1 and 79.4 \(\pm\) 3.5% (\(n\) = 17) in filter 2 of set I (Figure 6). Efficiencies of BOD\({}_{5}\) removal for filters in the set II were from 56.7 \(\pm\) 4.7 (\(n\) = 4) to 66.7 \(\pm\) 0.0% (\(n\) = 3) (Figure 7). The outflow BOD\({}_{5}\) values were in the range between 5.0 mg O\({}_{2}\) dm\({}^{-3}\) and 60.0 mg O\({}_{2}\) dm\({}^{-3}\) in the case of set I and between 10.0 mg O\({}_{2}\) dm\({}^{-3}\) and 60.0 mg O\({}_{2}\) dm\({}^{-3}\) in the case of set II. The P\({}_{\rm tot}\) removal efficiencies of set I and set II were shown in Figure 8.  
Figure 8: Total phosphorus (P\({}_{\rm tot}\)) removal efficiency in set I (**a**) and set II (**b**) during the experiment. Figure 6: Biochemical oxygen demand (BOD\({}_{5}\)) inflow and outflow concentrations (**a**) and removal efficiencies (**b**) for set I.  
Figure 7: Biochemical oxygen demand (BOD\({}_{5}\)) inflow and outflow concentrations (**a**) and removal efficiencies (**b**) for set II. The inflow \(\rm P_{tot}\) concentrations were: \(6.4\pm 0.7\) mg \(\rm dm^{-3}\) (\(n=18\)) and \(4.2\pm 0.3\) mg \(\rm dm^{-3}\) (\(n=7\)) for set I and set II, respectively (Figures 9 and 10). Efficiencies of total phosphorus removal (\(\rm P_{tot}\)) were: \(61.2\pm 3.3\%\) (\(n=17\)) in filter 1 and \(60.2\pm 2.8\%\) (\(n=18\)) in filter 2 of set I (Figure 9). Effectiveness of total phosphorus removal was: \(52.9\pm 7.0\) (\(n=5\))-\(73.3\pm 1.6\pm 2.8\%\) (\(n=7\)) for filters in the set II (Figure 10). The outflow total phosphorus concentrations were in the range between 1.2 mg \(\rm P_{tot}\)\(\rm dm^{-3}\) and 3.9 mg \(\rm P_{tot}\)\(\rm dm^{-3}\) in the case of set I and between 0.8 mg \(\rm P_{tot}\)\(\rm dm^{-3}\) and 2.5 mg \(\rm P_{tot}\)\(\rm dm^{-3}\) in the case of set II. The removal efficiencies of TSS were shown in Figure 2:0  
Figure 2:1 Total suspended solids (TSS) removal efficiency in set I (**a**) and set II (**b**) during the experiment.