Two types of geotextile, TS 50 and TC/PP 300, were investigated as experimental filters. The raw wastewater, pre-treated in a septic tank, was intermittently dosed and filtered under hydrostatic pressure. At the beginning, the filter reactor comprised nine filters made of geotextiles (of three types: TS 10, TS 50 and TC/PP 300). At the end of the start-up period the TS 10 filters were removed due to their high outflow instability. After four months of working, the hydraulic capacities of the remaining filters were: 3.23 cm3/cm2/d for TS 50 and 4.14 cm3/cm2/d for TC/PP 300. The efficiencies of COD and BOD5 removal were similar for both types of geotextile (COD: 64%, BOD5: 80%). A small but statistically significant difference between ammonium nitrogen removal was observed (40% for TS 50 and 35% for TC/PP 300), most probably due to their different structure. Biological removal of P(tot) was relatively poor and similar for both geotextile types. The mean concentration of matter accumulated on the geotextiles was over one order of magnitude higher than conventional activated sludge concentrations. During the last weeks of the experiments the values of basic pollution indicators in the effluent were lower than the maximum permissible values (according to Polish law).

This article presents a small diameter gravity sewerage system in a rural area. In this system, domestic wastewater was preliminarily treated in septic tanks equipped with outlet filters, so the effluent features were similar to those of clear water. Additionally, some outlets were equipped with floating-ball check valves to avoid backflow. One of the pressure mains was used as a gravity collector conveying septic tank effluent in the direction of the pumping station during pump idle time. The operation of the system was simulated using SWMM computer code. The simulation results were validated for data obtained from part of a sewerage system in Kolonia Zolkiew and Rozki village consisting of two pumping stations and 86 serviced households using polyethylene pipes of outer diameter 50–63 mm. The results of the measurement of the outflows from one pumping station are presented. The simulation results showed good agreement with the empirical data, especially after several simulation days. The greatest discrepancy during the start-up period was the consequence of the initial conditions describing the empty pipework. Thanks to storage in the pump sumps, septic tank and pipes, as well as their smart operation, a relatively uniform inflow to the pumping stations was achieved. Simulations in SWMM showed that there is still potential to optimize the sewerage system through more adequate pump selection and pipe diameters.

The article presents modern methods of hydraulic design of an innovative small diameter gravity sewerage system. In this system, domestic wastewater is preliminary treated in septic tanks equipped with outlet filters, thus the effluent features are similar to those of clear water. Innovative non-return valves at the outlets eliminate introduction of air to the system and thus the flows can be treated as one-phase ones. Computer codes EPANET 2 and SWMM 5.0 were applied and compared. Two flow schemes typical for the sewerage system were implemented in EPANET 2, and the third -in a slightly modified SWMM 5.0. Simulation results were validated on empirical data obtained on a laboratory physical model, consisting of four tanks of minimum volumes 600 dm 3 each, connecting PE pipelines of diameters 25 mm and 36 mm and relevant sanitary fittings. Water inflows, typical for domestic wastewater outflows from single homesteads, were provided by a pump. Water flows were measured using water meters with pulse outputs, and water levels in tanks by pressure transducers. Hydraulic characteristics of filters and non-return valves were provided. Simulation results showed good agreement with the empirical data. Ranges of values of design parameters, needed for successful application of both codes, were established and discussed.

The aim of the study was to describe in a mathematical manner the hydraulic capacity of textile filters for wastewater treatment at changeable wastewater levels during a period between consecutive doses, taking into consideration the decisive factors for flowconditions of filtering media. Highly changeable and slightly changeable flow-conditions tests were performed on reactors equipped with non-woven geo-textile filters. Hydraulic conductivity of filter material coupons was determined. The dry mass covering the surface and contained in internal space of filtering material was then indicated and a mathematical model was elaborated. Flow characteristics during the highly changeable flow-condition test were sensitivity to differentiated values of hydraulic conductivity in horizontal zones of filtering layer. During the slightly changeable flow-conditions experiment the differences in permeability and hydraulic conductivity of different filter (horizontal zones) height regions were much smaller. The proposed modelling approach in spite of its simplicity provides a satisfactory agreement with empirical data and therefore enables to simulate the hydraulic capacity of vertically oriented textile filters. The mathematical model reflects the significant impact of the filter characteristics (textile permeability at different filter height) and operational conditions (dosing frequency) on the textile filters hydraulic capacity.M. Spychała, M. Pawlak, T. Nawrot 422There are many factors and conditions related to non-woven geo-textile hydraulic conductivity and clogging. Some of these are well known: fibre density [Marks 1975], filtered suspension particle size [Gourc and Faure 1990] and organic material growth or deposition [Hoogerdendorn and Van der Meulen 1977].The studies conducted thus far [Spychała et al. 2013] showed a satisfactory pollution removal by textile filters for wastewater treatment (TFWT).The average values of removal efficiencies can seem to be relatively low, however much higher values were observed occasionally under slightly changeable conditions (inflow concentrations): up to 89% for COD, 80% for ammonium nitrogen and up to 48% for total phosphorus. Taking into consideration that this type of filter operates without forced (energy consuming) aeration and sophisticated solutions are not applied, it can be considered as satisfactory in its performance.TFTW hydraulic conditions are complex due to the dosing regimen related to changeable wastewater surface level (which causes changeable hydrostatic pressure). Another flow-related condition is the stratification of biomass (the mixture of live organisms and solids originated from wastewater) concentration and their resistance along the filter layer height (filtering surface is oriented vertically) due to the clogging process. However it is worth noting that the TFWT is a specific filtering medium operating under specific conditions and therefore both internal clogging and surface accumulation (in the form of filter cake) occurs.The form of biomass inside th...

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