Fat, Oil And Grease Research Articles

Preparation of polyelectrolytes for wastewater treatment

Liquid-phase polymerisation of acrylamide-acrylic acid to form polyelectrolytes used in wastewater cleaning was examined using accelerated electron beam and microwave irradiation methods. Polymerisation was carried out in aqueous solutions at temperatures ∼60 °C. Monomers total concentration was established at 40% (36% acrylamide and 4% acrylic acid). Only using the features of simultaneous radiation–induction and microwave heating can result in the formation of linear polymer chains with good water solubility and low residual monomer concentration. The flocculation capacity of the obtained polymers was tested using two wastewaters, one sampled from a slaughterhouse and the other from a vegetable oil plant. Quality indicators such as total suspended matters (TSM), chemical oxygen demand (COD), biological oxygen demand (BOD) and fat, oils and grease (FOG) were measured before and after the treatment with polymeric flocculants and compared with the results obtained in classical treatment with Al 2(SO 4) 3. It was found that the combined treatment with polymers and Al 2(SO 4) 3 increases the degree of purification of both wastewaters up to 99%.

The Aerobic Treatment of Grease-Containing Fast Food Restaurant Wastewaters

Fast food restaurants typically produce a low volume grease-containing wastewater, generated by their daily kitchen activities, for which there is currently no acceptable treatment technology. This paper describes the performance of a novel bioreactor, the weir tank reactor, for the treatment of fast food restaurant wastewater at an organic loading rate (OLR) of 5 kg wastewater m -3 d -1 . Two different mixed microbial cultures (one designated MC1, the other an activated sludge), were used together with fast food grease residues from two different sources (Woking, Surrey, and Birmingham, West Midlands). The reactor achieved a high (84–96%) removal of FOG (fats, oils and greases) irrespective of the microbial inoculum, the source of the FOG or the alkalinity (low or high) of the water. This high performance was attributed to a combination of the effective mechanical mixing regime and the periodic removal of a portion of microbial solids from the weir tank reactor liquor, in the form of an effluent, during the weir tank reactor studies.

Fatty acid separation from hydrolyzer wastewater by ultrafiltration

AbstractA fatty acid emulsion wastewater containing approximately 3,500 mg/L of inedible Fats, Oil and Grease (FOG) is treated at 280 L/min by ultrafiltration (UF) to yield a clear permeate with 390 mg/L FOG and a free fatty acid oil phase product. The UF flux rates are 2 m3/m2‐day, with a 3 to 7 day period of operation between membrane cleanings. The system recovers approximately 900 Kg of fatty acids per day at a cost of $1.13 per Kg recovered, including both capital and operating costs, and enables the plant to comply with its wastewater pretreatment permit for Fats, Oil and Grease.

Plant experience using hydrogen peroxide for enhanced fat flotation and bod removal

AbstractHydrogen peroxide (H2O2), is known in the food processing industry to reduce COD, BOD, to prevent anaerobic conditions in pipes, tanks and lagoons and to remove malodorous sulfides in effluents from anaerobic wastewater treatment. It has recently been shown to also provide effective solids removal from food processing wastewater. The wastewater of food processing plants often contains a very high loading of organic material consisting of fat, oil and grease (FOG), resulting in unacceptable BOD and COD levels. Since many wastewater treatment systems are being pushed to the limit of their capacity or are already overloaded, the high FOG loading cannot be removed well by the conventional means of treating the wastewater with dissolved air flotation or grease traps. As a result, many food processors are paying surcharges for not being in compliance with the tight discharge limits. To overcome these problems, a process has been developed using H2O2 for enhanced FOG recovery and BOD removal. The process is based on the formation of microbubles which attach themselves to the FOG particles and float them to the surface where they can be easily skimmed off. In addition to meeting effluent standards, the process has been able to yield a material that is very renderable and suitable for reuse. Technical and operational data of several industrial applications in the U.S. and Canada are presented, together with process costs. H2O2 treatment will generally be most applicable when improvement of solids removal is required without major investment costs, e.g. emergency situations, during seasonal peaks or increased production.

Pretreatment of Poultry Processing Wastewater in a Pilot-Scale Anaerobic Filter

Wastewater from a typical poultry processing plant in the southeastern U.S.A. was treated on site with a pilot-scale anaerobic packed-bed reactor. The reactor had a working volume of 3.2 m3, was filled with 15-cm diameter polyethylene random-pack media, and was operated at 35°C with a retention time of 21 hours and at a loading rate of 2.8 kgCOD/m3d−1. Under these conditions, treatment efficiencies were sufficient to meet typical surcharge-free municipal discharge requirements, with effluent soluble COD of 440 mg/L, soluble BOD5 of 190 mg/L, fats, oil and grease (FOG) of 10 mg/L, and total suspended solids of 140 mg/L. Results from pilot operation are compared to those of previous laboratory-scale studies, where similar results were obtained with less than half of the hydraulic retention time. Differences in treatment on pilot vs. laboratory scale were largely due to differences in wastewater variability and reactor operation. Recommendations for future studies to reduce the costs of treatment, including emphasis on types of low-cost packing, amounts of packing media, and heating requirements are presented.

Evaluation of procedures for measuring fats, oils and greases (FOG) in wastewaters

Abstract Fats, oils and greases (FOG) represent a major contituent of municipal and industrial wastewaters. Analytical procedures for this parameter present problems of reliability and convenience. This study was conducted to compare a continuous liquid‐liquid extraction procedure with currently accepted standard procedures.

Treatment of combined and raw sewages with the dissolved air flotation process

Daily, sewage treatment works (STWs) receive large volumes of fats, oils and greases (FOG), by-products of food preparation. To increase FOG removal at STW, conventional primary sedimentation tanks (PSTs) can be enhanced using chemical coagulant or through dissolved air flotation (DAF) techniques. This work aimed to assess the potential benefits of enhanced primary treatment for FOG removal through an energy and costs analysis. To achieve this, a five-year sampling programme was conducted monthly at 15 STWs measuring FOG concentrations in crude and settled sewage (i.e. after primary treatment). In addition, two DAF pilot systems were trialled for four months and their performance, in terms of FOG removal, was assessed and compared to that of a control primary clarifier. Across the 15 STWs, influent FOG concentrations were found at 57 ± 11 mg.L−1. Chemical coagulants dosed prior to PSTs increased FOG removal rates on average to 71% whilst traditional sedimentation only achieved 50% removal. Effluent FOG concentrations were found between 12–22 mg.L−1 and 19–36 mg.L−1 respectively. By contrast, DAF achieved FOG effluent concentrations on average at 10 ± 4 mg.L−1 corresponding to 74% removal from a relatively low influent concentration of 40 ± 30 mg.L−1. Thus, enhanced primary treatments have the potential to reduce organic load to secondary treatment and increase energy generation through anaerobic digestion. The overall net energy balance was estimated at 2269 MWh.year−1 for the DAF compared to 3445 MWh.year−1 for the chemically-enhanced PST making it a less financially attractive alternative. Yet, in the case where the works require upgrading to accommodate flow or load increases, DAF appeared as a sensible option over sedimentation offering significantly lower capital costs and footprint. In relation to FOG management, upgrading all STWs is not realistic and will require understanding where the benefits would be the highest.