Treatment of Effluents from Food Services Establishment (FSEs) by Physico-chemical Processes: A Case Study for Trinidad & Tobago

In Trinidad & Tobago, it is estimated that approximately 231,304 kg/day of unaccounted for FOG-bearing wastewaters from Food Establishments, are released into the environment with no method of viable treatment in the country. This seeks to find a financially viable and optimal physico-chemical processes for the treatment of emulsified FOGs, for subsequent release into the environment. Bench-scale studies analysed the characteristics of FSE’s effluents from three popular sources, studied the treatment using Jar Tests experiments, and subsequent pilot plant study. The mean concentration of constituents in the FSEs’ samples were FOG (511 mg/l ± 116 mg/l), Suspended Solids (446 mg/l ± 146 mg/l), Chemical Oxygen Demand (2229 mg/l ± 963 mg/l) and pH (6 ± 0.3). Jar Tests were conducted using Poly-aluminium Chloride (PACl) as coagulant, anionic and cationic polyelectrolytes as flocculant aids with suitable pH adjustments of samples to determine the isoelectric point for the coagulant. FOG removal levels of 99.9% resulted in a final effluent concentration of 0.17 mg/l, which was within the regulatory standard of 20 mg/l. Required conditions were a PACl concentration of 250 mg/l, followed by flocculation aid with 4 mg/l of 0.1% low cationic polyelectrolyte (CP 1154) at pH adjusted to 8, and post-sedimentation for thirty minutes. The Jar test results were used as the basis for the design of a pilot-scale treatment plant. The plant achieved a 97.4% removal of FOG (residual of 16.8 mg/l) using 0.1% medium cationic polyelectrolyte (CP1156) and pre- and post-sedimentation times of 120 minutes, and 360 minutes, respectively.