Treating Bakery Wastewater

Bakery wastewater typically contains high loadings of suspended solids, fats, oils and grease (FOG), and a high biochemical oxygen demand (BOD). Due to the complex nature of this wastewater it requires a multi-step solution.

First, a pretreatment stage is almost always required to remove large solids, gloves, hairnets, etc. Then, a chemical treatment step is required to break bonds between surfactants (which are typically cleaning solutions) and fats, oils and grease. Charges at the surface of suspended solids and FOG are neutralized, causing the solids, fats, oils and grease to become unstable and precipitate out of solution. A polymer is then added to bind the solids and FOG together to form what’s known as "sludge." The sludge has a high surface area at this point and can be settled or floated out of the water using a clarifier or Dissolved-Air-Floatation (DAF) system.

However, a solid removal pretreatment solution is insufficient to meet total effluent criteria. The next challenge is to reduce the Biological Oxygen Demand (BOD) levels to within the stringent effluent permit limits. This is because of the presence of soluble (dissolved) BOD sources like sugar and proteins. Even cleaning solutions can contribute to BOD. If a bakery needs to discharge treated water with a low BOD, a biological treatment system is required.

Biological wastewater treatment can be complicated for bakeries because every bakery needs to keep its equipment and processing lines clean and disinfected. A careful review of the chemicals used in the cleaning process is necessary, as certain disinfecting chemicals can inhibit microbial growth in the biological treatment system, even in small quantities. Among the most detrimental to biological systems are quaternary ammonium compounds, or quats for short. These disinfectants are very effective at disinfecting the bakery’s equipment but are toxic to the friendly microbes in the biological treatment system. If used, it will invariably lead to a malfunctioning biological system. Since only small quantities are required to inhibit most biological growth, quats can render a biological treatment system completely ineffective.

Disinfecting chemicals that break down or become consumed in the process of disinfecting are ideal for use at bakeries that use biological treatment systems. Some of these chemicals may include, Peracetic Acid (PAA), Hydrogen Peroxide (H2O2), and even weaker solutions of bleach. The goal must be to effectively disinfect inside the bakery, yet, allow the wastewater to be treated using microorganisms. These microorganisms are the only cost-effective way to removed dissolved substrates like sugar, protein, alcohol and other organic pollutants from wastewater. A bakery with its own biological treatment system becomes in-effect, like a mini-sewage treatment plant. The waste in the water may be somewhat different, but the type of treatment and the principles of operation are the same.

If you operate a food processing plant and are in need of wastewater treatment solutions, please consider Ecologix Environmental Systems as your source for expert solutions and high quality treatment systems. Ecologix has a wealth of experience in the engineering and fabrication of wastewater treatment systems. We design and build nearly every system we provide. Ecologix also operates its own internal laboratory that has tested and developed chemical solutions for hundreds of clients arounds the world. We are truly a one-stop shop for all your water treatment needs.