Marjana Simonič

Coagulation and UF treatment of pulp and paper mill wastewater in comparison

A study using coagulation-flocculation and ultrafiltration (UF)methods for pulp and paper mills’ wastewater (WW)was carried out. The reduction efficiencies of turbidity and chemical oxygen demand (COD), the removal efficiency of total suspended solids (TSS) and absorbance at 254 nm were the main evaluating parameters. Using coagulation-flocculation, the efficiencies of alum and polyaluminum chloride (PACl)were studied, when used alone and when coupled with flocculant aids. During the coagulation-flocculation process, use of a single coagulant, the coagulant dosage, and the pH, play an important role in determining the coagulation efficiency. At the optimum PACl dosage of 840 mg L−1 and optimum pH of 9.0, turbidity reduction was found to be 94.5%. A combination of inorganic coagulant and flocculant, or polymer was applied, in which PACl was used coupled with the polyelectrolytes Organopol WPB20 and WPB40. PACl coupled with Organopol WPB20 by optimal pH 9 gave a 98.3% reduction of turbidity, 91.9% removal of TSS, and a 60.2% reduction in COD. Ultrafiltration trials were carried out on a pilot scale. A tubular module was used with ceramic membrane. This membrane is a multi-channel membrane with an active surface layer made of Al2O3 and ZrO2. Within the acidic range, the turbidity and TSS were removed at above 99%.

Ultrafiltration of oil-in-water emulsion by using ceramic membrane: Taguchi experimental design approach

In this study, a Taguchi experimental design methodology was used to determine the importance of process parameters influencing the ultrafiltration (UF) of oil-in-water emulsions. Four parameters including pH (5–11), oil concentration (φ) (0.5–3% (v/v)), temperature (T) (25–45°C) and trans-membrane pressure (TMP) (1–5 bar) were studied at three levels. The highest flux was used as optimization criterion. In order to reduce the number of experiments, a Taguchi method was applied. Analysis of variance (ANOVA) was used to determine the most significant parameters affecting the optimization criterion.Filtration experiments were performed in a cross-flow operation at a total recycle condition in a laboratory-scale plant. The ceramic UF membrane with a pore size of 50 nm was employed in a tubular module with an active area of 0,418 m2. We used water-soluble cutting oil mixed with water as a model oil-in-water emulsion. During the experiment, the drop size and zeta potential distributions were evaluated.The optimum conditions for UF providing the highest flux were found at TMP = 5 bar, pH = 7, and φ = 0.5 v/v%. The pH of emulsion had the highest impact on COD retention. The results of this study could be used as a guideline for operating UF systems with ceramic membranes at optimal conditions.

A pilot-scale microwave technology for sludge sanitization and drying

Large volumes of sludge are produced from onsite sanitation systems in densely populated areas (e.g. slums and emergency settlements) and wastewater treatment facilities that contain high amounts of pathogens. There is a need for technological options which can effectively treat the rapidly accumulating sludge under these conditions. This study explored a pilot-scale microwave (MW) based reactor as a possible alternative for rapid sludge treatment. The reactor performance was examined by conducting a series of batch tests using centrifuged waste activated sludge (C-WAS), non-centrifuged waste activated sludge (WAS), faecal sludge (FS), and septic tank sludge (SS). Four kilograms of each sludge type were subjected to MW treatment at a power of 3.4 kW for various time durations ranging from 30 to 240 min. During the treatment the temperature change, bacteria inactivation (E. coli, coliforms, Staphylococcus aureus, and enterococcus faecalis) and sludge weight/volume reduction were measured. Calorific values (CV) of the dried sludge and the nutrient content (total nitrogen (TN) and total phosphorus (TP)) in both the dried sludge and the condensate were also determined. It was found that MW treatment was successful to achieve a complete bacterial inactivation and a sludge weight/volume reduction above 60%. Besides, the dried sludge and condensate had high energy (≥ 16 MJ/kg) and nutrient contents (solids; TN ≥ 28 mg/g TS and TP ≥ 15 mg/g TS; condensate TN ≥ 49 mg/L TS and TP ≥ 0.2 mg/L), having the potential to be used as biofuel, soil conditioner, fertilizer, etc. The MW reactor can be applied for the rapid treatment of sludge in areas such as slums and emergency settlements.

Purification of a contaminated thermal well at an oil drilling site

The thermal water from the well MT‐4 in Northeast Slovenia contains many organic micropollutants of geogenic origin because of the nearby oil fields. Therefore, a special technological treatment was necessary to make the water suitable for bathing: consisting of flocculation, sand filtration, and adsorption on granular activated carbon. We managed to remove not only all potentially toxic organic substances, but also the mesophilic bacteria (CFU) as well as sulfite reducing bacteria. On the other hand, all the important physical chemical parameters of water remained practically unchanged. In this way a hygienic water quality for balneological purposes was obtained. ©1999 John Wiley & Sons, Inc. Environ Toxicol 14: 211–216, 1999

Thermal water treatment with granular activated carbon

The object of this article is to discuss the purification of a special thermal water of a geogene origin, containing potentially toxic, organic micropollutants like benzene, toluene, mesitylene, xylene and phenols. As the flotation of the thermal water on model laboratory equipment did not remove all toxic organic substances present from water, a granular activated carbon (GAC) filter column was used. Although the use of granular carbon adsorption is well known in potable water treatment, in industrial water polishing and waste water treatment, there is no information about its use for the purification of special thermal water. The result of the purification with GAC adsorption is thermal water with quality that corresponds to requirements of DIN 19643 for bathing water. After this treatment thermal water reached the hygienic quality of drinking water and could be used for balneological purposes.

Alternative cleaning of compost leachate using biopolymer chitosan

Compost leachate poses a threat to the environment because it contains many organic and inorganic pollutants. Chemical Oxygen Demand (COD) has been reported at values above 5000 mg/l O2. Heavy metals, such as nickel, lead, chromium are also present within these waters. Thus, in order to comply with the increasingly stringent environmental quality standards such contaminants must be removed effectively. The research approach in this paper is directed towards chelating pre-treatment procedures. Nontoxic and biodegradable biopolymer chitosan was used as a chelator for the removal of dissolved metals from compost leachate. The influence of chemical conditions regarding the chelation efficiency was studied in model solutions. The optimal treatment conditions were applied onto compost leachate which was analysed further regarding metals. In addition, the influence of chitosan was studied on compost leachate toxicity. The most important aspect of this paper is to demonstrate the potential of waste chitosan recycling. Thus, the chitosan chelates were subjected to the electrospinning procedure in order to develop new nano-porous structures, such as, for example, conductive textiles.

Compost leachate treatment using polyaluminium chloride and nanofiltration

Abstract Laboratory scale filtration tests utilizing leachate were conducted to investigate fouling and filtration performance of nanofiltration membranes. The work presented in this study is conducted on real samples rather than model water. Physico-chemical analyses showed that the leachate contained a lot of organic substances, exceeding 20000 mg/L O2 expressed as chemical oxygen demand. Proper pre-treatment method must be chosen in order to reduce fouling index. Coagulation pre-treatment using poly-aluminium chloride was chosen. Two thin film polysulfone membranes were used, purchased by Osmonic Desal. The focus of this research is to assess the influence of the particle size and zeta-potential of the colloidal fraction in leachate on nanofiltration performance. The isoelectric point of both membranes was 4.7 and 4.3, respectively. The fouled membranes were negatively charged over the pH range with isoelectric point shifting to the left (lower pH) indicating the foulant material mainly not charged. It was confirmed by its zeta-potential, measured at -2 mV.

The influence of electrogalvanic device on scaling

AbstractThe use of an electrogalvanic device for scale neutralisation is descibed in this paper. Physico-chemical analyses were performed before and after the treatment. The results were compared with those obtained by using magnetic water treatment device. By measuring some individual parameters and the implementation of chemical analysis, the satisfactory functioning of the electrogalvanic device was demonstrated. The quality of drinking water did not change much after the water treatment method. The results of determination of calcium carbonate saturating index showed that the raw drinking water is in carbonate equlibrium as well as both treated water samples. The calcite/aragonite ratio was studied by means of microscopy and X-ray powder diffraction. Inspection of crystals formed during the experiments with microscopy indicated that aragonite crystal structure of the precipitates prevailed over the calcite stucture. The diffractograms showed that the share of aragonite increased after using the electrogalvanic device compared with raw drinking water samples where the share of calcite was higher.

Uncertainty of nitrate and sulphate measured by ion chromatography in wastewater samples

This paper presents an evaluation of measurement uncertainty regarding the results of anion (nitrate and sulphate) concentrations in wastewater. Anions were determined by ion chromatography (EN ISO 10304-2, 1996). The major sources of uncertainty regarding the measurements’ results were identified as contributions to linear least — square or weighted regression lines, precision, trueness, storage conditions, and sampling. Determination of anions in wastewater is very important for the purification procedure, especially the amount of nitrate in waste and potable waters.The determined expanded uncertainty was 6.1 % for nitrate anions and 8.3 % for sulphate anions. The difference between measurement uncertainties determined by the two methods, the weighted and linear least — square methods, is negligible.

Microfiltration of cutting-oil emulsions enhanced by electrocoagulation

Electrocoagulation (EC) was examined as a pre-treatment to the microfiltration (MF) of oily emulsions within the metalworking industry. The aim of this pre-treatment was to improve the MF performance in terms of flux decline and removal of oil by applying the minimum time of EC pre-treatment. Aluminium electrodes were used in EC, and flat sheetregenerated cellulose membrane in MF. The experiments were carried out using cutting-oil emulsions at different concentrations (0.1, 0.5 and 1.0% (v/v)) and conductivity of about 700 μ Sc m −1 . Drop size and zeta potential distributions were carried out to evaluate the impacts of EC time on zeta potential and average particle size. We found that in all emulsions, 10 min of EC made the average size of oil particles bigger than the average size of the pores in MF and substantially reduced pore clogging and irreversible fouling. Reduced flux decline was related to the continuous formation of Al(OH)3 in EC that interconnected the colloidal oil particles into porous and irregularly shaped flocs which formed highly porous cake layer on the membrane surface.