Proceedings

Energy intensive technologies are used to treat dissolved COD present in wastewater.
Moreover, the use of traditional technologies produces large amounts of sludge, which require
further treatment and adds to the energy and cost of the process. In responding to the
challenges of reducing energy usage and greenhouse gas emissions, new approaches to
resource recovery and for minimizing the environmental footprint are being examined. This
paper reports an investigation of adsorption processes as potential solutions for wastewater
treatment.

Rather than promoting the loss of COD to CO2, H2O and other simple products, it would be
beneficial to recover the organic carbon allowing the generation of energy, and thereby
reducing the overall cost. For designing any physicochemical wastewater treatment technique,
an understanding of wastewater, specifically the chemistry of the COD, is required. Solid phase
extraction (SPE) technique is used to characterise the dissolved COD fraction of settled sewage.
Based on the SPE results different media were evaluated.

To achieve this, batch studies were conducted using GAC, PAC, PolyChrom CEREX and granular
sludge as potential sorbents for the sequestration of different components of the dissolve
organic fraction present in the wastewater. A breakthrough curve was obtained by plotting
fraction of COD remain in the final discharge versus volume of wastewater treated. The effect of
temperature, pH, particle size, contact time and COD concentration on equilibrium time were
also investigated. Different strategies were employed to recover the captured COD in a
concentrated stream to allow the COD to be utilised for VFA production or digestion. Out of the
four media tested, the best phase chemistry for capturing dissolved COD was reverse phase,
followed by adsorption and then strong anion exchange.

Introduction:

Typical Municipal wastewater constitutes 99.9% of water and rest in the form of solids. Total
solids are consisting of suspended and dissolved organic and inorganic contents. Organic
substances present in sewage are of different nature like Proteins, fats, carbohydrates, lignin,
soaps, synthetic detergents and their decomposition products (Turovskiy and Mathai 2006).
Depending upon the location and sources of wastewater, treatment plant also receives various natural and synthetic organic chemicals from the process industries. Characterisation of
wastewater in terms of individual compounds is hectic, tiring cumbersome task because of
presence of wide range of natural and xenobiotic compounds and their concentration variation.
The treatment capacity and treatment efficiency of systems are calculated based upon the
influent concentrations and the effluent requirements (Gross 2005). For designing any
physicochemical wastewater treatment technique a complete understanding of wastewater in
terms of chemistry of compounds present in it is desired. Information regarding fraction of
polar, non-polar and ionic compounds present in wastewater will help us in choosing suitable
media and process for its removal. Wastewater characterisation using Solid phase extraction
(SPE) is an increasingly useful, quick and simple technique. SPE is used to overcome the
limitation such as incomplete phase separations, less-than-quantitative recoveries in
liquid/liquid extraction. Apart from usage of expensive, breakable specialty glassware it is not
also good from green chemistry point of view as it required large volumes of solvents. As per the
information of authors not much work is reported in literature on Wastewater characterisation
in term of polar, non-polar, ionic species using SPEs. SPE tubes were used in place of batch
studies in order to use the data generated for the column operations. In SPE tubes wastewater
at the top end is contacted continuously by fresh solution of constant concentration. Based on
the SPE results different commercially available media were evaluate and compare on the basis
of their sorption capacity. Batch and column adsorption experiments were conducted to
investigate the removal of COD from wastewater by PicaBiol, Resinex TPX-4500, NORIT GAC
1240W and Aquasorb 2000. The results obtained will help in designing process model for
dissolve COD removal using suitable material prior to ASP. The effective materials could also be
employed in different combinations to determine the best order for application.