Jean Hall

Electro-kinetic technology as a low-cost method for dewatering food by-product

Increasing volumes of food waste, intense environmental awareness, and stringent legislation have imposed increased demands upon conventional food waste management. Food by-products that were once considered to be without value are now being utilized as reusable materials, fuels, and energy in order to reduce waste. One major barrier to the valorization of food by-products is their high moisture content. This has brought about the necessity of dewatering food waste for any potential re-use for certain disposal options. A laboratory system for experimentally characterizing electro-kinetic dewatering of food by-products was evaluated. The bench scale system, which is an augmented filter press, was used to investigate the dewatering at constant voltage. Five food by-products (brewers spent grain, cauliflower trimmings, mango peel, orange peel, and melon peel) were studied. The results indicated that electro-kinetic dewatering combined with mechanical dewatering can reduce the percentage of moisture from 78% to 71% for brewers spent grain, from 77% to 68% for orange peel, from 80% to 73% for mango peel, from 91% to 74% for melon peel, and from 92% to 80% for cauliflower trimmings. The total moisture reduction showed a correlation with electrical conductivity (R2 = 0.89). The energy consumption of every sample was evaluated and was found to be up to 60 times more economical compared to thermal processing.

Stabilization of a railway embankment using electrokinetic geosynthetics

Abstract A trial was conducted on a Victorian embankment to evaluate the use of electrokinetic geosynthetics for embankment stabilization. The embankment had been constructed by end tipping London Clay fill onto unprepared ground and has a history of instability. Ground investigations indicated a core of firm material underlain by softened embankment fill and alluvium and overlain by softened material towards the ground surface. The slope was treated to a maximum of depth of 7 m using electrokinetic geosynthetics and electrokinetic soil nails. Over a period of 42 days, electrokinetic treatment forced water out of the ground by raising it >4 m above the initial groundwater level such that discharge from activated electrokinetic prefabricated vertical drains (ePVDs) was >25 times that of control drains. Cation exchange processes were active as part of the treatment and correlated with reductions in plasticity and shrinkage. Overall DC power consumption was approximately 11.5 kWh m−3 of soil treated. Post treatment boreholes demonstrated that the soft material beneath the embankment had become firm and exhibited apparent improvements in both undrained and drained strength parameters. Pull-out tests on electrokinetic soil nails demonstrated an improvement in the bond strength of the nails by an average of 263%. Inclinometer data showed a significant reduction of movement tending to zero after treatment.

Discharged filtrate movement in food materials under application of electrokinetics

Orange juice (OJ) and malt extract (ME) samples were treated using an electrokinetic (EK) application to investigate the impact of the pH/Lowest conductivity point (LCP) ratio of experimental materials on the water profile direction and the anolyte to catholyte filtrate ratio. After applying the electric field through samples between two electrodes, filtrate was discharged mainly towards the anode in OJ samples (acidic medium, pH/LCP < 1) and towards the cathode in ME samples (alkaline medium, pH/LCP > 1). Adjusting the orientation of electrodes depending on the results maximised dewatering efficiency under EK by 7.8% in OJ and 11.8% in ME. Changing the pH/LCP ratio by adjusting the starting pH improved dewatering efficiency under EK by 25.7%. The results are used to develop theoretical guidelines to help determine the water profile direction and filtrate outlets for different food materials based on their pH and LCP values. EK is an effective method for dewatering food materials.

Dewatering Sludge Using Electrokinetic Geosynthetics

Many industries create sludges as a waste product. Dewatering of these fine grained slurries is often problematic and the traditional outlets of lagoons or landfill may pose stability and environmental contamination issues. Sludges may be mineral based or organic based. Mineral based sludges created by mining processes are currently deposited into lagoons. These tailings are often very soft and poorly consolidated thus they may create an environmental hazard and even pose a severe safety threat, particularly in seismically active areas. The treatment and disposal of organic based sludges (sewage sludge) is one of the most problematical issues affecting waste water treatment in the developed world. The traditional outlets for sewage sludge are to spread it on agricultural land, or to form a cake for deposit to landfill or incineration. In order to create a sludge cake, water must be removed. Existing dewatering technology based on pressure can only remove a very limited amount of this water because of the way in which water is bound to the sludge particles or flocs. Sewage sludge lagoons, although smaller than tailings ponds still pose an environmental hazard or impede redevelopment.