In this paper, the preliminary study on the impact of filamentous particles (FP) in the septic tank effluent (STE) on filter cake (FC) development was presented. The number, length and diameter (30 p./cm3, 451 and 121 microm, respectively, on average) of FPs were measured using microscope image analysis of STE samples condensed using a vacuum evaporation set. Results of this study showed, that 0.73% of volatile suspended solids (VSSs) mass from the STE occurs in the form of FPs. No correlation between FP total mass and VSS was found. An experiment with a layer of FPs simulated by ground toilet paper was conducted and showed the impact of this layer (4.89 mg/cm2) on wastewater hydraulic conductivity--for an FC with FPs (FC-FP), hydraulic conductivity was seven times lower than for the FC without the FP layer, and on outflow quality (lower concentration of organic matter expressed as chemical oxygen demand (COD) in effluent from the FC-FP filter than in the effluent from the FC filter: 618 and 732 gO2/m3, respectively). Despite a relatively small amount of FPs in STE solids (as volume fraction), they play an important role in FC development due to their relatively high length and low degradability. Probably relatively small pores of the FC containing FPs (FC-FP) caused a small particle blocking and a decrease in permeability.
Physicochemical studies on wastewater quality and microscopic analyses of activated sludge are necessary to properly evaluate the condition of activated sludge. The aim of this study was to evaluate the application of the sludge biotic index to determine when a change in treatment quality is short-lived, caused by, e.g., a change in influent quality or quantity, and when it indicates adverse changes in the biocenosis of activated sludge, which would very likely result in the lower efficiency of wastewater treatment in the near future. The objects of the study were two identical parallel running small wastewater treatment plants. The following indicators of contamination were analyzed: the chemical oxygen demand (COD), biochemical oxygen demand (BOD 5 ), and total suspended solids (TSS). The authors additionally carried out a microscopic analysis. The study confirmed a correlation between the sludge biotic index and the removal efficiency of COD and BOD 5 ; however, no correlation was found between the sludge biotic index and the removal efficiency of total suspended solids. The presence of metazoan microorganisms coincided in time with a good effluent treatment efficiency. When their quantity declined, a decrease in the efficiency of wastewater treatment was also observed.
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...
In recent years in Poland the dynamic growth of declarations by local government concerning onsite wastewater treatment plants (WTPs) can be observed. These systems are popular in rural areas, where the building of sewerage systems is not recommended for economic and technical reasons. At the end of 2013 the declared onsite WTPs number was approximately 155 thousand [Environmental protection, Central Office of Statistics (GUS), Poland, 2005-2014], and about 125 thousand of these were installed in rural areas [Municipal infrastructure GUS, 2003-2013] (Figure 1). In recent years the annual growth of declared onsite WTPs can be seen in the range of 20-30 thousand. The septic tank (ST) is usually the first part of the onsite WTP. The purification of wastewater in a ST occurs during the slow flow of wastewater through the tank, mainly thanks to three
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