Effect of substrate concentration on biodegradation of 2,4-dichlorophenol using modified rotating biological contactors

Abstract

2,4-Dichlorophenol used in the manufacture of pesticides, germicides, resins, seed disinfectants and antiseptics, if disposed untreated causes greater havoc for land and aquatic environment. In all the earlier works, 2,4-dichlorophenol has been fed along with easily biodegradable substrate, glucose as one of the constituents. A modi®ed 4-stage RBC was used for the biodegradation studies of 2,4-dichlorophenol. The micro organisms attached to the disks were specially acclimatised to the extent that the 2,4-dichlorophenol alone serves as the sole carbon source supporting their metabolic activities. The RBC was operated at 12 rpm. The toxic substrate removal studies were carried out in the hydraulic loading rates ranging from 0.005 m 3 /m 2 /d to 0.035 m 3 /m 2 /d and organic loading rates from 0.35 g/m 2 /d to 6.15 g/m 2 /d. A correlation plot between 2,4-dichlorophenol removal and organic loading rate is presented. A mathematical model is proposed using regression analysis. List of symbolsA m 2 total surface area of the discs D m Submerged disc depth F Removal of 2,4-dichlorophenol expressed as a fraction L gm A2 d A1 In¯uent organic loading Q m 3 m A2 d A1 hydraulic loading rate S mgl A1 In¯uent 2,4-dichlorophenol concentration W rpm rotational speed F hr hydraulic detention time T°C wastewater temperature 1 Introduction 2,4-dichlorophenol (DCP) is used extensively in the manufacture of herbicides, pesticides, resins and wood preservatives. DCP can be found in the environment in degraded herbicides, saw mills, wood waste incinerators and hazardous waste sites. DCP can cause death, respiratory failure, bone marrow atrophy and skin damage in animals and confers a bad taste and odour to food and water. Literature is available for biodegradation of different type of wastes ranging from domestic sewage, to industrial wastes like distillery, tapioca, sugar cane etc; using RBC technology. But very few reports are available for biological degradation of toxic phenolic waste wasters using RBC. Huang et al. (1985) studied the RBC treatment of phenol-formaldehyde resin waste waters. Pilot scale RBC's at various in¯uent phenol levels as high as 600 mg/l were used in this study. Results showed that average phenol removal rates were about 99 percent. Tokuz (1991) used RBC for studying the biodegradation of phenolic compounds such as 2-chlorophenol, 2,4-dichlorophenol, 2,4,6,-trichlorophenol; pentachlorophenol, 2-nitrophenol, diethyl phthalate and dibutyl phthalate. This study reveals that the phenolic compounds are biodegradable and RBC process is a viable process in treating phenolic waste waters. Radwan et al. (1997) used laboratory scale modi®ed RBC for studying the organic removal of 2,4-dichlorophenol waste waters. The concentration of 2,4-dichloropheonal treated was 200 mg/l and the removal ef®ciency was reported as 99.2%. In this study, DCP was spiked along with the synthetic sewage containing glucose as one of the constituents. The advantages of RBC is that, easy adaptability for small to medium type installations, sim...

Para-chlorophenol containing synthetic wastewater treatment in an activated sludge unit: Effects of hydraulic residence time

“…Recent investigations on biodegradation of chlorophenols focused on the use of immobilized cells or biofilm reactors (Shieh et al, 1990;Radwan and Ramanujam, 1996;Shin et al, 1999;Swaminathan and Ramanujam, 1998;Kim et al, 2002, Xiangchun et al, 2003Ranganath, 2005, Kargi et al, 2005), since biofilm reactors are more resistant to high concentrations of chlorophenols. Suspended culture systems have considerable advantages over the biofilm systems such as better aeration, control and easy operation as compared to the biofilm reactors.…”

Attached-growth process engineering in wastewater treatment

“…A modi®ed 4-stage rotating biological contactors (RBC) was used for the biodegradation studies of 2,4-dichlorophenol [30]. It was a laboratory model made of ®ber reinforced plastic, having a central spindle made of stainless steel.…”

Biological treatment of synthetic wastewater containing 2,4 dichlorophenol (DCP) in an activated sludge unit

“…Pre-adaptation of the activated sludge cultures to chlorophenols was reported to improve the rate and the extent of biodegradation of those compounds (Bali and Sengul, 2002;Sahinkaya and Dilek, 2002). Recent investigations on biodegradation of chlorophenols focused on the use of immobilized cells or biofilm reactors (Shieh et al, 1990;Radwan and Ramanujam, 1996;Shin et al, 1999;Swaminathan and Ramanujam, 1998;Kim et al, 2002). Biofilm reactors are more resistant to high concentrations of chlorophenols, because of high biomass concentrations and diffusion barriers within the biofilm for the toxic compounds.…”