# A Preliminary Study on the Use of Xylit as Filter Material for Domestic Wastewater Treatment
## 2 Materials and Methods
### Treated Media, Their Dosing, and Collection  
The septic tank effluent used for the study was obtained from an on-site wastewater treatment plant consisting of a septic tank and soil infiltration system, collecting and treating domestic wastewater generated by a four-person household. The wastewater was collected as a septic tank effluent.  
The proportions of components of the seminatural greywater (GW) used in the study were 31%, 62%, and 7% of laundry, bath or shower, and washbasin, respectively. The seminatural greywater comprised 12 dm\({}^{3}\) of natural laundry greywater collected from the washing machine effluent after washing 2-5 kg of clothes (Ariel, Procter, and Gamble, Warsaw, Poland) mixed with artificial greywater simulating bath/shower greywater, prepared using: 3.6 g of shampoo (Head & Shoulders, Procter and Gamble, Warsaw, Poland), 5.7 g of shower gel (Colgate-Palmolive, Warsaw, Poland), 0.4 g of liquid soap (Serpol-Cosmetics Ltd., Miescisko, Poland) and 27 dm\({}^{3}\) of tap water. The total water hardness in tap water used was 275 mg CaCO\({}_{3}\)/dm\({}^{3}\).  
During the preliminary stage, the filtration columns were fed with septic tank effluent. In this stage, the columns were fed with a volume of about 20 cm\({}^{3}\) of wastewater every hour. During stage I, the filtration columns were fed with septic tank effluent; however, they were fed every two hours (with a volume of about 20 cm\({}^{3}\)).  
After collection, the STE was transported to the laboratory and stored in a chamber of 20 dm\({}^{3}\) at room temperature for a few days (up to 7 days). This suggests that thanks to the extended retention time and increased temperature, there occur processes that often take place in practice (high-temperature periods, vacation users' absence).  
During stage II, the filtration columns were fed with GW with a volume of about 20 cm\({}^{3}\), every two hours. The raw GW was prepared twice a week. The collection and measurements of wastewater quality indicators in raw GW were carried out no later than one day after supplying the retention chamber with a new dose of a new portion of media; hence, the retention time of media was about 24 h. The dosing schedule for raw and treated GW sample collection was as follows: 7:00, 9:00, 11:00, and 13:00, for the dosing of GW into the filters and 8:00, 10:00, 12:00, and 14:00, for the dosing of GW into the beakers.  
The assumed hydraulic load during the preliminary stage was about 30-40 cm\(\cdot\)d\({}^{-1}\) (20-25 cm\({}^{3}\) every hour per 15.2 cm\({}^{2}\) of inner filtering column surface area), and during stages I and II, about 15-20 cm\(\cdot\)d\({}^{-1}\) (20-25 cm\({}^{3}\) every 2 h).  
These filtering columns were fed with STE and GW using pumps controlled by a programmable timer.  
Xylit (xyloid lignite) used in this study comprised carbonised wood fibres derived from lignite. The raw lignite blocks were crushed to 10-30 mm pieces ('scraps') and raw lignite 'angel hair' was crushed to 20-40 mm pieces before being used as a filter material in the experiment.  
During the study (usually on a weekly basis, with a few deviations, such as holidays, a holiday break) measurements of hydraulic capacity (outflow rate) and qualitative analyzes of inflow and outflow media (STE or GW) were carried out in terms of total suspended solids (TSS), five-day biochemical oxygen demand (BOD\({}_{5}\)), chemical oxygen demand (COD), ammonium nitrogen (NNH4) and total phosphorus (P\({}_{\text{tot}}\)). Outflows were measured twice or three times a week.