Edyta Łaskawiec

THE USE OF MEMBRANE TECHNIQUES IN SWIMMING POOL WATER TREATMENT

The paper has determined the suitability of membrane processes (UF ultrafiltration, UF, and nanofiltration, NF) for the purification of waste streams, so-called backwash water, obtained from washing filtration beds in a swimming pool water system. The backwash water samples were taken from the circuits located in two indoor facilities with a different purpose of the basins. Moreover, the samples were characterized by varying quality, as described by selected physicochemical parameters (such as turbidity and ultraviolet absorbance UV254). Commercial membranes were used for the tests. The transport-separation properties of the membranes were determined based on the volumetric flux of the permeate. In addition, backwash water samples before and after the membrane process were subjected to toxicological assessment using the Microtox® screening test. The performed processes contributed to a significant reduction in turbidity and the value of UV254 ultraviolet absorbance, both in the ultrafiltration and nanofiltration processes. Whereas, significant differences in transport properties were noted within individual processes. A great influence of backwash water quality, including physicochemical parameters, on the course and results of the membrane filtration processes was demonstrated. In all of the nanofiltration cycles carried out, the removal of the toxic properties of the backwash water with respect to bacteria in the Microtox® test was found. Nevertheless, samples with high values of resultant physicochemical parameters after the ultrafiltration process were still characterized by high toxicity. Pressure membrane processes show high effectiveness in the removal of contaminants from backwash water. However, it is necessary to introduce supporting processes aimed at reducing membrane pore blocking by deposits and organic compounds, and in the case of ultrafiltration, assuring the safety of the purified stream in terms of the toxicological effect.

Ultrafiltration for Purification and Treatment of Water Streams in Swimming Pool Circuits

The paper presents possible applications of pressure-driven membrane processes for treatment of swimming pool water and purification of waste streams – washings. Newly identified swimming pool water quality issues are presented that require a modernization of existing technologies. The studies used polymer membranes with the same particle distribution range (50000 Da), but made of different membrane-forming materials: polyvinylidene difluoride (PVDF) and polyether sulfone (PES) for purification of washings. The ultrafiltration process allowed obtaining a high turbidity reduction rate in washings (over 95%), and also a significant reduction of total organic carbon. The effectiveness of the PES membrane was reduced after the process commencement, whereas the separation capacity of the PVDF membrane increased during the studied filtration process. While setting the operational process parameters consideration should be given also to the resistance of used membranes to chlorine present in the swimming pool water. A prolonged exposure of the polyether sulfone membrane to chloride may have caused its gradual damage and degradation of its separation properties.

Elimination of Bisphenol A from Wastewater through Membrane Filtration Processes

New priorities for the environment have resulted in a reassessment of modern technology for treatment of urban wastewater. Urban wastewater treatment mainly involves the elimination or reduction of anthropogenic organic micropollutants in the aquatic environment. In this paper, the effectiveness of bisphenol A elimination from wastewater, after biological treatment, through a complex ultrafiltration/reverse osmosis purification process was evaluated. The effectiveness of the wastewater treatment process in the tested system was also evaluated with a number of other physical and chemical analyses for pH, turbidity, colour, absorbance, TOC, phenol index, conductivity and the concentration of selected heavy metals. Within this study, the change in the hydraulic performance of the membranes was also investigated. The effectiveness of the reduction of bisphenol A concentrations during the process of ultrafiltration was small, due to the significant difference between the size of the pores of the membrane and the size of eliminated micropollutants. In the process of reverse osmosis, the wastewater treatment system reported that the concentration of bisphenol A was reduced by 68%. In the tested treatment system, the ultrafiltration/reverse osmosis completely removed colour, lead and chromium. Other contaminants were eliminated by more than 31%. In both membrane processes, there was evidence that the membrane pores were blocked, but this occurred to a greater extent during the process of reverse osmosis.

TREATMENT OF POOL WATER INSTALLATION WASHINGS IN A FLOCCULATION/ULTRAFILTRATION INTEGRATED SYSTEM

The article presents the possibilities of employing an integrated flocculation/ultrafiltration system in the treatment of washings generated upon the rinsing of filter beds in pool water installations. Single ultrafiltration process was used as a comparator. Flocculation was carried out using commercial dialuminium pentahydroxychloride solution widely used at pool facilities for the removal of contaminants in flocculation processes. The studies consisted in determination of correlations between the conditions of the flocculation process (variable doses of Al3+ ions: from 4 to 280 mg/L) and the transport/separation characteristics of ultrafiltration membranes. Flocculation was performed at different temperatures of washings i.e. 8, 21, and 30°C for each of the pre-defined doses. Ultrafiltration was highly capable of reducing the turbidity of washings and removing a large group of contaminants as determined by turbidimetry and UV254 absorbance measurements. The studies revealed that the best transport/ separation characteristics of ultrafiltration membranes were obtained in a system in which ultrafiltration was performed following flocculation of washings carried out at 21°C using a 40 mgAl3+/L solution. The turbidity was reduced by ca. 99% and UV absorption was reduced by ca. 94% while the relative volumetric stream of the permeate increased by more than 35% (as compared to the filtration of washings in a singleprocess system). Membrane ultrafiltration significantly increased the quality of the waste stream consisting of washings from the pool water installation. Pre-processing of washings is required before ultrafiltration in order to limit the blocking of membrane pores. Flocculation may be one of such pre-processing methods.

THE MUNICIPAL SEWAGE TREATMENT PLANT EFFLUENT POLISHING IN ULTRAFILTRATION

The effluent from the municipal sewage treatment plant was comparatively treated in the ultrafiltration process using ceramic and polymer membranes. Filtration was carried out in the cross-flow system under the conditions of the transmembrane process pressure of 0.1 MPa in the case of the ceramic membrane and 0.2 MPa with the polymer membrane, at a temperature of 20°C. The effectiveness of the process has been assessed by means of various physical and chemical analyses (pH, turbidity, color, absorbance, TOC and phenol index). The toxicological assessment (by applying the bioluminescent bacteria Aliivibrio fischeri as an indicator organism) and microbiological assessment of tested samples were included. The hydraulic efficiency of membranes was studied during filtration. Is was specified that the efficiency of the process depends on the conditions of membrane filtration, wherein the better effects of the removal of organic pollutants have been noted in the case of polymer membrane than with the ceramic membrane. However, the polymer membrane, in comparison to the ceramic membrane, was more susceptible to pore blocking, which caused the reduction of hydraulic efficiency. Regardless of the type of membrane, the permeates were not toxic and did not contain microorganisms.