Wastewater Treatment in Food Production Facilities

In industry, large volumes of water are often required to support their respective processes.   As a result, a large portion of that water will get contaminated and must be treated prior to its release back into the environment.

Within food processing plants, the manner in which water gets contaminated will vary, however, some of the more common modes are described as follows.

• Ingredient/raw material spills
• Bleed off of spent or off-spec materials from intermediate processing steps
• Overflow or component/material release from finished goods during cooking
• Cleaning & sanitation activities

It goes without saying, where possible, source control is of paramount importance. If there is an opportunity to segregate and remove a source contaminant or at the very least, minimize its concentration in the wastewater, every effort should be made to do so. This in turn will reduce the number of processing steps needed to treat the waste and ensure operational costs are held at manageable levels.

For any impurities that make it into the wastewater, its type and the form in which it is present is of significant importance .   For example, in most food plants, waste materials are characterized as being “Insoluble” or “Soluble” impurities. Insoluble impurities are relatively easy to remove by employing some form of liquid, solid separation (primary treatment). Soluble impurities are not so easily removed and often require some form of biological oxidation  (secondary treatment). If soluble impurities are present in high concentration, the complexity of a WWT plant will increase significantly, as will its corresponding operating costs. A plant’s decision to pursue treatment to this extent will be based largely on their ability to stay within the municipal limits, negotiate an amenable surcharge agreement and account for the inevitable fines that will be incurred when exceedances are measured.

To give us a better feel for some of food-based impurities that fall into each category of waste, the following have been listed.

Insoluble impurities

• suspended solids
  • breaded materials
  • granular solids (flour, baking soda, cocoa, etc.)
  • broken/fragmented raw, intermediate or finished goods
• fats, oils & grease
  • butter, cooking oils, lard, margarine, shortening etc.

Soluble (dissolved) impurities

• sugars, brines & syrups
• cleaners, surfactants and chelated materials
• products of decay (alcohols / organic acids)
• nitrogen bearing salts/preservatives
• metals & minerals

When faced with the reality that some form of wastewater treatment will be required, the preference is to try and meet discharge and operational targets solely through the application of liquid, solid separation. This often involves some form of screening, filtration, sedimentation and/or floatation. In some cases, sludge dewatering is used but the decision to apply it is largely based on the amount of waste sludge that is produced and the costs tied to its disposal. The diagram below provides an example of some of the more common pieces of equipment that are used to treat wastewater in some of the more standard food plants that are in operation today.

Used alone or in combination, the effectiveness of the equipment being used is heavily dependent on the following.

• Relative size and concentration of the particulate solids or immiscible materials that are present.
• The degree to which immiscible or slightly miscible materials (fats, oils, greases, organic/fatty acids) are emulsified or chemically bound.
• The amount of surfactant or chelating material present (sanitation).

As one can appreciate, chemistry can have a notable influence on the way impurities are either introduced or subsequently removed from wastewater. If sanitation chemistries are used to clean and remove impurities, WW treatment chemicals must be applied to promote their removal as they transition into the wastewater.

Coagulant and flocculant chemistries are commonly used to promote the removal of impurities from wastewater. When added, each will carry out the following functions.

Coagulants

• neutralize charge stable solids
• salt out any surfactants and/or chelating compounds
• break emulsions
• precipitate out, fatty acids and inorganic materials

Flocculants

• promote the formation of large floc structures by sweeping and bridging coagulated solids together.
• maintain structural integrity within the floc so the solids can be effectively removed and subsequently dewatered

If applied properly, a well-defined accumulation of large discrete suspended solids in clear water will appear. Once present, their removal is subject to the operational performance of the equipment that is in place and the operating conditions they are subject to.

It’s never easy to look at an existing system or “soon to be constructed” facility and intuitively know what your wastewater treatment needs will be. Thankfully, there are professionals out there who can provide you with the insight and support you need.

Aquasan has a well-versed team of experts and a product portfolio that is more than capable of meeting your operational needs. If called upon, Aquasan can provide support in the following ways.

• Characterize untreated wastewater and work in conjunction with WW equipment suppliers to identify the treatment needs (chemical and mechanical) of a new facility.
• Survey, assess and take corrective actions to try and improve operational performance when an existing WWT facility is struggling to meet its established discharge targets.
• Innovatively apply chemistries in ways that will maximize removal efficiency, maintain operational reliability and ensure chemical spend is proportional to the operational need.

At Aquasan, your success is ours. We are here to help!