Phenolic compound wastes from a large number of industries big and small which are highly toxic and pose a direct threat to human and aquatic life are generally let into the rivers and coastal waters. 2,4-dichlorophenol is used in the manufacture of industrial and agricultural products such as pesticides, germicides, soil sterilants, seed disinfectants and antiseptics. A modified Rotating Biological Contactor (RBC) was used for the treatability studies of synthetic 2,4-dichlorophenolic (2,4 CP) wastewaters. The RBC used was a four stage laboratory model and the discs were modified by attaching porous netlon sheets to enhance biofilm area and volume. Synthetic wastewaters were prepared with influent concentrations from 40 to 200 mg/l of 2,4 CP. Four hydraulic loads were used in the range of 0.024 to 0.065 m3.m\2.d\1 and the organic loads used were in the range of 2 to 13 g 2,4 CP.m\2.d\1. The RBC was operated at a speed of 12 rpm. Effect of hydraulic loadings and influent 2,4-dichlorophenol concentration on 2,4-dichlorophenol removal were discussed and showed maximum organic removal at hydraulic loads of 0.024 and 0.046 m3.m\2.d\1. Also, a correlation plot between 2,4 CP applied and 2,4 CP removed was presented. A mathematical model was proposed using regression analysis. List of symbols IntroductionOne of the industrial wastes of serious consequence from the point of water pollution is the phenolic compounds wastewater from the manufacture of industrial and agricultural products such as pesticides, germicides, soil sterilants, seed disinfectants and antiseptics. There have been considerable contributions to the knowledge on RBC technology over the last decade. The literature, however, contains limited information on the RBC treatability of toxic organic wastes. There are only a limited number of reports available on the RBC treatment of phenolic industrial wastewaters. Tabak, et al. (1981) studied the biodegradability of 96 compounds using ''static-culture flaskscreening'' method. Even though this method can not be directly compared to the wastewater treatment process, some of the findings are of interest. They found that the chlorinated and nitrated phenols were significantly biodegradable wastes. Tischler and Kocurek (1983) examined the effectiveness of biological treatment in removing toxic organic pollutants from chemical industry wastewaters. Operational data from activated sludge treatment systems operated by five organic chemical manufacturing plants were compiled and evaluated. Sixty toxic organic pollutants including 2,4 dichlorophenol was detected in wastewater samples. The average removal rate was 91%. Congram (1976) studied the treatment of petroleum refinery wastewaters using a 4-stage RBC. He reported that the influent and effluent phenol concentrations were 2.65 and 0.12 mg/l, respectively, which is equivalent to a removal efficiency of 95.5 percent. Huang et al. (1985) studied the RBC treatment of phenol-formaldehyde resin wastewaters. Pilotscale RBCs and various influent phenol levels (in some ca...

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...

A laboratory-scale hybrid UASB reactor, which combined an UASB in the lower part and a ®lter in the upper part, was used for the treatment of distillery spentwash. The reactor was operated under ambient conditions for 380 days. Using anaerobically digested sewage sludge as a seed, the start-up of the reactor and the cultivation of active granular sludge was completed within three months period. Scanning electron microscopic (SEM) observation of the granules showed the presence of Mehtanonthrix-like bacteria as the dominant species. Following the start-up the organic loading rate (OLR) was increased, stepwise, to 36 kg COD/m 3 á d at a constant hydraulic retention time (HRT) of 6 h. COD removal ef®ciency was 80% even at a high OLR of 36 kg COD/m 3 á d. Biogas rich in methane content (80%), with a maximum speci®c biogas yield of 0.40 m 3 CH 4 /kg á COD was produced. Polypropylene pall rings ®lter medium in the upper-third of the reactor was very effective as a gas-liquid-solid (GLS) separator, and retained the biomass in addition. The study indicated that hybrid UASB is a very feasible alternative for the treatment of high-strength wastewaters like distillery spentwash. IntroductionAn aerobic wastewater treatment (AWT) is becoming an accepted technology, not only for the treatment of variety of wastewaters but also for the environmental protection and recovery of renewable resources, particularly after the development of high-rate anaerobic reactors [1]. These reactors achieve the separation between hydraulic retention time (HRT) and solids retention time (SRT), thereby making an application of signi®cantly high volumetric loading rates possible. Various types of high-rate anaerobic reactors such as anaerobic ®lter (AF), down¯ow stationary ®xed ®lm (DSFF) reactor, up¯ow anaerobic sludge blanket (UASB) reactor,¯uidized bed (FB) and expanded bed (EB) reactors have been developed. Hybrid UASB [2] is among the newer designs which combines the advantages of UASB and AF concepts. In literature, hybrid UASB is also called as sludge blanket ®lter (SBF), up¯ow sludge blanket ®lter (UBF), hybrid up¯ow anaerobic sludge blanket (HUASB) reactor and the up¯ow anaerobic¯oat-ing bed (UAFB) or more simply anaerobic hybrid reactor.In India, there are over 200 distilleries [3] producing annually approximately 10,000 million litres of spentwash or vinasse. The distillery waste in the form of spentwash is amongst the worst pollutants produced by any industry both in magnitude and strength (BOD 5 ³ 30000 mg/l). It has been a cause of concern in India for the past few decades. In developing and tropical countries such as India, anaerobic digestion of high-strength wastewaters like spentwash becomes more attractive. Various anaerobic systems such as conventional digester, open lagoon, AF and two-staged ®xed ®lm reactor have been attempted for the treatment of distillery spentwash with a limited success. Applicability of hybrid UASB, which is considered most suitable for series of soluble and partially soluble wastewaters [4], appears to b...

High-strength organic waste like distillery spentwash can be effectively treated by electrolysis in the presence of sodium chloride. Because the graphite anode and stainless steel cathode zones were kept unseparated, chlorine produced during electrolysis forms hypochlorous acid. The hypochlorous acid thus formed oxidizes the organic matter present in the wastewater. The COD removal from the spentwash was found to be 99% for an initial COD concentration of 15 000 mg/L at the end of 240 min of electrolysis. The energy requirements were found to be 36 and 27 W·h/L for treating 20 L of spentwash at 2.5 and 3% sodium chloride concentration, respectively. The observed energy difference is due to improved conductivity of the electrolyte.

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