J. Bohdziewicz

The application of reverse osmosis and nanofiltration to the removal of nitrates from groundwater

Abstract The intensive development of agriculture and application of chemicals led to the contamination of many natural water reservoirs and groundwaters with nitrates. This paper reviews an attempt at removal of nitrate ions from tap water by means of the combined processes of reverse osmosis and nanofiltration. In the first stage, the water was filtered on nanofiltration membranes which resulted in the absence of bivalent ions in the obtained permeate. Then the filtrate was concentrated using reverse osmosis. Because the substances forming membrane scale (CaSO4, CaCO3) were removed from the filtrate, the efficiency of this process was limited mainly by the osmotic pressure of the retentate.

Application of pressure-driven membrane techniques to biological treatment of landfill leachate

Abstract The treatment strategy of landfill leachate is not easy to define in general terms due to differences, involving its composition, dumping place, and age of wastes. Since it is of specific type, characterized by high loading caused by refractive compounds, organic and inorganic substances, they are much more difficult to treat in comparison with municipal sewage. For this reason, the application of hybrid processes is advantageous, because, they enable the treatment of all contaminants present in the leachate. Preliminary tests of sanitary landfill leachate were carried out, using the following hybrid systems: activated sludge-chemical oxidation, activated sludge-ultrafiltration-chemical oxidation and activated sludge-ultrafiltration-reverse osmosis.

Removal of nitrates from ground water by a hybrid process of biological denitrification and microfiltration membrane

Abstract Removal of nitrates from ground water in a hybrid process of biological denitrification and microfiltration is discussed. The most favourable parameters for a culture of denitrifying bacteria with respect to organic carbon/nitrate nitrogen (C/N) ratio and nitrate loading have been determined. A capillary module was selected on the basis of the amount of biomass retained during microfiltration. The optimum operational parameters of microfiltration on the selected membrane module were determined. The installation used for denitrification consisted of a bioreactor and a membrane module made of capillary fibres. This was fed continuously for several months with a fluid medium containing organic carbon (methanol), nitrates and biogenic elements.

Removal of chromium ions (VI) from underground water in the hybrid complexation-ultrafiltration process

Transport and separation properties of ultrafiltration membranes made from polyacrylonitrile have been characterized and their suitability for chromium ion (VI) removal from underground water by means of complexed hexadecylpyridine chloride has been evaluated. It has been found that membranes of a 17.5% polymer content retain 98% of the chromium complex (VI) while the remaining ions present in water pass to the permeate. Tests which aimed at determining the most favourable amount of a complexing substance in relation to the amount of chromium ions (VI) and the optimum pH of the solution for which a retention coefficient of the chromium complex (VI) was the highest have been conducted. The results obtained confirmed that the complexation-ultrafiltration system presents an effective method for chromium ion (VI) removal from abyssal water.

Biodegradation of phenols and cyanides using membranes with immobilized microorganisms

Abstract The immobilization of microorganisms on ultrafiltration membranes made from polyacrylonitrile modified chemically with hydrazine hydrate and glutaraldehyde and their application to the biodegradation of phenol and cyanide contained in industrial wastewaters was examined. Three types of microorganism isolated from a mixed population of activated sludge adapted to phenol and cyanide decomposition were immobilized. Simulated phenol and phenol-cyanide wastewaters with a concentration of xenobiotics equal to their concentration in coke sewage were subject to ultrafiltration. The membranes were operated at a pressure ranging from 0·5 × 105 to 2·5 × 105 Pa, at a constant temperature of 298 K and a constant stirring rate in the bioreactor of 250 rpm. The results obtained were characteristic of each immobilized strain. The membrane with a mixture of microorganisms from the strains Agrobacterium radiobacter, Staphylococcus seiuri and Pseudomonas diminuta immobilized on its surface appeared to be the most effective. The coefficients of phenol and cyanide biodegradation were 36 and 20·3%, respectively.

Biological treatment of meat industry wastewater

The work aimed to determine the effectiveness of the treatment of wastewater generated by the meat industry in a hybrid system combining biological methods of activated sludge (in an SBR reactor) and reverse osmosis. The tests carried out on the wastewater from the meat processing plant Uni-Lang in Wrzosowa showed that the biological treatment resulted in sufficient removal of contaminants from the wastewater, which consequently could be discharged into receiving water. In order to make it possible for the wastewater to be reused in the production cycle, it was additionally treated with reverse osmosis. The research was described mathematically by the program MATLAB using artificial neural networks. The program enables a prediction of the results for the treatment of wastewater over a range of tested values.

Removal of nitrate ions from natural water using a membrane bioreactor

The research aimed at determining effectiveness of nitrates removal from natural ground water in a membrane bioreactor (MBR) with capillary polymer membranes. The paper presents an influence of nitrate loading on denitrification in an anaerobic packed-bed reactor, a sanitary and epidemiological analysis in a culture apparatus and effectiveness in removal of microorganisms from a post-culture effluent during microfiltration. The installation used for denitrification, which contained a bioreactor and membrane module made of capillary fibers, was fed continuously for several months with natural ground water enriched with organic carbon (methanol).

Porous polycarbonate phase-inversion membranes

Abstract This paper presents a method of preparation of phase-inversion porous polycarbonate membranes as well as experimental data on their structure and transport and separation properties. From a casting solution containing 8% of polycarbonate in a mixture of dioxane and dimethylformamide (mass ratio 3: 2), it is possible to obtain porous membranes by the phase-inversion method. Gelation should be carried out in an atmosphere of air saturated with water vapour. The porosity of the membranes can be controlled by the time and temperature of gelation. The obtained membranes are reasonably symmetrical, having a spongy structure with identical pore sizes and a skinned external structure. They retain macromolecules and suspended substances to a degree which depends on the nature of the solutes and on the pressure.

Kinetics and equilibrium of the sorption of bisphenol A by carbon nanotubes from wastewater

The aim of this study was to determine the sorption potential of carbon nanotubes (CNTs) to bisphenol A (BPA) contained in synthetic wastewater whose composition corresponds to biologically treated effluents. These nanotubes differed in their outer diameter, the number of graphene layers and the presence of modifying functional groups. Based on the nitrogen adsorption-desorption isotherms, mensuration of the specific surface area and pore size distribution was undertaken. The porous structure of the CNTs was bidispersive; the majority consisted of micropores, there was an average fraction of mesopores, and macropores did not occur. On the basis of common kinetics models (pseudo-first-order and pseudo-second-order models), a trial of modelling the kinetics of BPA sorption onto nanotubes was undertaken. The experimental data were well fitted only to the pseudo-second-order models. The kinetics study indicated that adsorption of BPA on CNTs proceeded very fast, with the majority of the adsorbate being adsorbed in the first few seconds. The sorption capacity of nanotubes to BPA was the highest for single-walled CNTs. A decrease in the sorption potential of the nanotubes for higher pH values occurred as a result of the deprotonation of the BPA and formation of bisphenolate anions, consequently leading to a decrease of π-π (hydrophobic) interaction and enhancing electrostatic repulsion. Overall, these results unequivocally confirm the ideal performance and potential of nanotubes for removal of micropollutants from synthetic wastewater. Replicating the conditions occurring in real wastewater allows us to expect a high sorption of BPA in real competitive sorption systems.

Application of the system which combines coagulation, activated sludge and reverse osmosis to the treatment of the wastewater produced by the meat industry

The wastewater from the meat industry was treated in the system linking the processes of: coagulation, biological treatment using the activated sludge method, simultaneous precipitation of phosphor and reverse osmosis. The carried out investigation studies showed that after the simultaneous precipitation of phosphor the sewage could be returned to the natural receiving water, since its pollution ratio did not exceed the permissible values for sewage waters which can be returned to natural receiving waters. By cleaning up the wastewater in the process of reverse osmosis, it was possible to use it again in the technological cycle.