# Preliminary Study on Greywater Treatment Using Nonwoven Textile Filters
## 2 Materials and Methods  
Experimental sets were located in the laboratory of Department of Hydraulic and Sanitary Engineering (Poznan University of Life Sciences, Piatkowska Str. 94 A, Poznan). The study was made at a temperature close to room temperature, however, some differentiation was observed (17-27 \({}^{\circ}\)C)). This was caused by window openings and central heating intensity fluctuation. The study was conducted from August 2017 till December 2018. From the last week of August till the beginning of October 2017, the initial start-up using tap water was performed in order to tightness of the set-up verification and flow rate (dosage volume) setting. Samples treated as greywater inflowing to filters were taken from reactors and outflowing--collected in beakers as dropping form filters (through the outflow pipes). Two sets of filters were used in the tests (Figure 1). The first set (set I) consisted of two filters: four-layer filter (filter 1) (3.6 mm thick, polyfelt TS 20 with a thickness of 0.9 mm each) and eight-layer filter (filter 2) (with a thickness of 7.2 mm). The dimensions of filters inside set I were: \(6.0\times 20.0\times 40.0\) cm (height). The reactor containing filters of set I was made of a PE panels, and its internal dimensions were: \(17.0\times 28.0\times 40.0\) cm. The filters of set I were made of geotextile wrapped around a plastic framework. The second set (set II) consisted of five filters (filter 1-filter 5) made of four-layer filtering material--polyfelt TS 20 (with a thickness of 3.6 mm). The reactor containing filters of set II was made of a PVC tube of 16.0 cm diameter and 40.0 cm long with five filters. The external diameter of a single filter was 2.36 cm and its height 35 cm. Non-woven geotextile (polyfelt TS 20) layers were glued on a galvanized steel grid with the dimensions of a single mesh of \(12\times 12\) mm. A few conclusions have been taken from building and operation of similar construction set-up used for septic tank effluent treatment [30], e.g., related to isolation--special gum rings have been used for connection of filters outflow pipes with the bottom of the reactor and geotextile coupons have been glued using specially dedicated glue. Figure 1: (**a**) Set I, (**b**) set II, and (**c**) scheme of nonwoven textile filter set (differences in dimensions between set I and set II and construction details are described in the main text of the article). The reactors were fed with greywater by a pump controlled by a programmable time controller, six times a day (every 4 h). Set I was fed with greywater of average volume 288 cm\({}^{3}\) to the maximum level of 20.0-25.0 cm and minimum greywater level was 9.0-12.0 cm. Set II was fed with greywater of average volume 500 cm\({}^{3}\) and operated at greywater levels: 20.0-23.0 cm (maximum) and 11.0-14.0 cm (minimum). Hydraulic capacity was calculated as the quotient of the outflow volume from a given filter and its active filtration surface per time unit. The second set (set II) dimensions have been changed comparing to the set I with the aim of reducing the total capacity of filters, however, the basic principles of technology and filters operation have remained unchanged. The geotextile properties used in both sets (trade name: polyfelt TS 20) were: thickness: 0.9 mm, surface mass: 125 g m\({}^{-2}\), specific surface area about 10\({}^{4}\) m\({}^{2}\) m\({}^{-3}\), opening size O\({}_{90}\): 0.105 mm (according to EN ISO 12956) [32], permeability at stress 2 kPa 115 dm\({}^{3}\) m\({}^{-2}\) s\({}^{-1}\). The set I during the start-up period was fed with septic tank effluent and after reaching the expected biomass concentration the filter set I was fed with greywater. The set II was fed during both the start-up period and during work period - with greywater. The aim of using two sets (set I and set II) was to compare the start-up period longevity. The set I was fed with STE, and then, with greywater. The set II was fed with greywater from the beginning of the experiment.