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The fate of lindane in the conventional activated sludge treatment process

A. M. Kipopouloua, A. Zouboulisb, C. Samara, and Th. Kouimtzisa

a Environmental Pollution Control Laboratory, Department of Chemistry, Aristotle University of Thessaloniki, GR-541 24, Thessaloniki, Greece
b General and Inorganic Chemical Technology Laboratory, Department of Chemistry, Aristotle University of Thessaloniki, GR-541 24, Thessaloniki, Greece

Received 3 February 2003; revised 4 July 2003; accepted 4 November 2003.




Abstract
A pilot-scale treatability study was performed to evaluate the fate of lindane (-hexachlorocyclohexane) in wastewater treatment plants operating in the conventional activated sludge mode. Different types of wastewater (industrial and municipal) spiked with variable lindane concentrations were used at different dosing rates in order to determine distribution and removal under various operational conditions. The major amount (67–91%) of lindane inputs to the treatment process was found to concentrate in primary sludge. A significant linear correlation between the compounds partition coefficient (logKp) and the organic fraction of primary sludge (foc) was found. Sorption on primary sludge solids was concluded to be the major removal mechanism. Only 0.1–2.8% of lindane inputs was concentrated in activated sludge. Lindane losses in primary treatment were low (4–26%). Higher losses (up to 61%) were observed during the biological treatment probably due to biodegradation. These losses were negatively correlated with the inflow rate of lindane into the aeration tank. Activated sludge aged about 23 d presented the maximum loss of lindane. Increased sludge age was associated with increased percentages of lindane in the final effluent.

Author Keywords: Activated sludge process; Lindane; Organochlorine pesticides; Wastewater treatment


Article Outline
1. Introduction
2. Materials and methods
2.1. Pilot plant description
2.2. Operational scenarios
2.3. Analysis of lindane
3. Results and discussion
3.1. Pilot plant performance
3.2. Distribution of lindane in the wastewater treatment plant
3.3. Phase partitioning
3.4. Mass balance of lindane
4. Conclusions
References


1. Introduction
Organochlorine pesticides (OCPs), including lindane (-hexachlorocyclohexane), have been recognized as a major environmental problem due to their widespread use in the past, their pronounced persistence against chemical/biological degradation, and their trend to bioconcentrate. Although most OCPs have been regulated during the past years, some are still used (probably illegally) or produced in many countries ([Jaffe, 1991]; [Ro and Libra, 1995]). OCPs are introduced into the environment mainly via diffuse sources (agricultural runoff), but also from point sources (production sites) ( [US EPA, 1979]; [Saleh et al., 1980]; [Petrasek et al., 1983]; [Hannah et al., 1986]; [Haverhoek et al., 1997]). OCPs may enter a wastewater treatment plant either due to the contribution of industrial discharge or as a component of urban runoff or drainage into the sewerage system ( [Petrasek et al., 1983]; [Haverhoek et al., 1997]; [Katsoyiannis and Samara, 2002]). The fate of these xenobiotic organic compounds in wastewater treatment plants will be governed both by the physico-chemical properties of the compounds and the process design and operating conditions of the treatment system ( [Bhattacharya et al., 1996]; [Mikkelsen et al., 1996]; [Jacobsen et al., 1996]; [Byrns, 2001]).

Literature data concerning the fate of lindane during the wastewater treatment process are relatively few and largely variable. It has been found to be recalcitrant to bio-oxidative activity of wastewater microbiota under a specific incubation method ([Tabak et al., 1981]), and poorly biodegradable by integrated activated carbon/activate