Wastewater Treatment in the Food industry
Dewatering Treatment In The Food Industry
What Is Dewatering?
Dewatering processes have become the forgotten part of food industry wastewater treatment. In many instances, wastewater treatment processes in the food industry are missing an important final stage i.e. dewatering.
Dewatering is defined as the removal of water from solid material by solid-liquid separation processes to produce drier cake.
Why Do I Need Dewatering?
In food wastewater processes, such as the treatment of waste from chicken abattoirs, the application of a dewatering method can equate to significant cost savings. Many food wastewater treatment plants have been installed without this final stage in an attempt to save capital costs to the detriment of operating costs.
Wastewater treatment processes e.g. Dissolved Air Flotation (DAF), produce a sludge that is high in water content e.g. 80 -90 %. This sludge cannot be discharged to the sewerage system or environment. Therefore, it will need to be removed from site, by a commercial carrier, for further treatment. Consequently, excess water is being removed and incurring costs unnecessarily. The costs of removal of this DAF sludge carried out by commercial waste companies includes not only cartage , labour and disposal costs but also government levies imposed on waste disposal .
Dewatering processes can reduce the water content in sludge by a substantial amount to give a cake that is 30% dry solids generating significant operational cost savings, by reduction in volume of sludge that needs to be removed from site. The water recovered from the sludge can be reused in the plant for a variety of applications, such as wash down water, with minimal further treatment, to produce a further benefit to the plant.
What Dewatering Options Are Available To The Food Industry?
There are a number of types of equipment, which can be used to dewater sludge and can be retrofitted to any wastewater plant. These include belt presses, filter presses and centrifuges. The final choice of equipment depends on the waste to be treated and the operational constraints of the plant.
The most common equipment in use in the food industry is the belt press. This is a relatively simple piece of equipment, based on the mangle principle of squeezing water from the waste via a series of rollers. This equipment has low maintenance costs and is adaptable to many types of food wastes.
Food wastes, which are not from primary production and involve further processing such a burger production and are high in oils and greases, may require more sophisticated dewatering movements such as the centrifuge, which operates using a high-speed vortex mechanism.
Filter or plate presses are only used in the food industry for difficult to dewater sludges. This equipment tends to have the highest capital and parts replacement cost.
The efficiency of all three dewatering options is enhanced by the addition of polymer flocculants. Cationic flocculants tend to be the most effective in the food industry.
The foot print space available is also an important consideration in the choice of dewatering methodology.
Buy or Lease Your Dewatering Equipment?
Dewatering equipment is available to purchase as a separate unit to retrofit to wastewater treatment plants and in many instances has a small footprint.
If capital expenditure is not available to upgrade your plant, a modern innovation is the facility to lease dewatering equipment. There are many options and companies available, which lease equipment for a variety of periods. Many companies provide packages tailored to suit operational needs or seasonal demand.
There is no reason nowadays for dewatering to be the forgotten part of food industry wastewater treatment. Nor is there any excuse for sloppy sludge to squander operational revenue.