Erkan Sahinkaya

Effects of 2,4-dichlorophenol on activated sludge

Abstract. The effects of 2,4-dichlorophenol (2,4-DCP) on both acclimated and unacclimated activated sludge were investigated in batch reactors. The IC50 values on the basis of maximum specific growth rate (µm), percent chemical oxygen demand (COD) removal efficiency and sludge activity were found to bexa072, 60xa0and 47xa0mg l–1, respectively, for unacclimated culture. The percent COD removal efficiencies of unacclimated culture were affected adversely, even at low concentrations, whereas culture acclimated to 75xa0mg 2,4-DCP l–1 could tolerate about 200xa0mg 2,4-DCP l–1 on the basis of COD removal efficiency. Although yield coefficient values of unacclimated culture increased surprisingly to very high values with the addition of 2,4-DCP, a linear decrease with respect to 2,4-DCP concentrations was observed for acclimated culture. Although no removal was observed with unacclimated culture, almost complete removal of 2,4-DCP up to a concentration of 148.7xa0mg l–1 was observed with acclimated culture. It was showed that the culture could use 2,4-DCP as sole organic carbon source, although higher removal efficiencies in the presence of a readily degradable substrate were observed. Culture acclimated to 4-chlorophenol used 2,4-DCP as sole organic carbon source better than those acclimated to 2,4-DCP.

The growth behavior of Chlorella vulgaris in the presence of 4-chlorophenol and 2,4-dichlorophenol.

Toxicity of 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP) on the growth of Chlorella vulgaris was investigated in batch reactors. Results revealed that 4-CP did not adversely affect the growth of algae up to 20mg/L, however higher concentrations inhibited growth appreciably and no growth was detected at 100mg/L. 4-CP also caused some physiological changes in the algal cells as increasing initial 4-CP concentration caused a linear decrease in chlorophyll a (chl-a) content of the cell. 2,4-DCP up to 20mg/L did not exert toxic effect on the growth of C. vulgaris, rather an induction effect was evident. Unlike a linear decrease with 4-CP, no exact correlation between 2,4-DCP concentration and chl-a content of the cell was observed, but it was certain that the presence of 2,4-DCP caused some physiological changes in the cell of C. vulgaris. No biodegradation of 4-CP and 2,4-DCP was observed over a 30-day incubation.

Modeling chlorophenols degradation in sequencing batch reactors with instantaneous feed-effect of 2,4-DCP presence on 4-CP degradation kinetics

Two instantaneously fed sequencing batch reactors (SBRs), one receiving 4-chlorophenol (4-CP) (SBR4) only and one receiving mixture of 4-CP and 2,4-dichlorophenol (2,4-DCP) (SBRM), were operated with increasing chlorophenols concentrations in the feed. Complete degradation of chlorophenols and high-Chemical oxygen demand (COD) removal efficiencies were observed throughout the reactors operation. Only a fraction of biomass (competent biomass) was thought to be responsible for the degradation of chlorophenols due to required unique metabolic pathways. Haldane model developed based on competent biomass concentration fitted reasonably well to the experimental data at different feed chlorophenols concentrations. The presence of 2,4-DCP competitively inhibited 4-CP degradation and its degradation began only after complete removal of 2,4-DCP. Based on the experimental results, the 4-CP degrader’s fraction in SBRM was estimated to be higher than that in SBR4 since 2,4-DCP degraders were also capable of degrading 4-CP due to similarity in the degradation pathways of both compounds.

Analysis of the best available techniques for wastewaters from a denim manufacturing textile mill

The present study was undertaken as the first plant scale application and evaluation of Best Available Techniques (BAT) within the context of the Integrated Pollution Prevention and Control/Industrial Emissions Directive to a textile mill in Turkey. A best practice example was developed for the textile sector; and within this context, BAT requirements for one of the Worlds leading denim manufacturing textile mills were determined. In order to achieve a sustainable wastewater management; firstly, a detailed wastewater characterization study was conducted and the possible candidate wastewaters to be reused within the mill were identified. A wastewater management strategy was adopted to investigate the possible reuse opportunities for the dyeing and finishing process wastewaters along with the composite mill effluent. In line with this strategy, production processes were analysed in depth in accordance with the BAT Reference Document not only to treat the generated wastewaters for their possible reuse, but also to reduce the amount of water consumed and wastewater generated. As a result, several applicable BAT options and strategies were determined such as reuse of dyeing wastewaters after treatment, recovery of caustic from alkaline finishing wastewaters, reuse of biologically treated composite mill effluent after membrane processes, minimization of wash water consumption in the water softening plant, reuse of concentrate stream from reverse osmosis plant, reducing water consumption by adoption of counter-current washing in the dyeing and finishing processes. The adoption of the selected in-process BAT options for the minimization of water use provided a 30% reduction in the total specific water consumption of the mill. The treatability studies adopted for both segregated and composite wastewaters indicated that nanofiltration is satisfactory in meeting the reuse criteria for all the wastewater streams considered.