A sustainable wastewater management plan is something every wastewater treatment facility should strive for. Sustainability is not simply being proactive in a few key areas, its taking holistic approach to reducing the overall impact on the environment.
In areas where fresh water sources are drying up, reusing wastewater back upstream in certain processes is a way for processing facilities to become sustainable from both an environmental and economic impact. Advancements in membrane filtration technologies has allowed for wastewater reuse to become a more economical choice than in years past.
Although in most Food & Beverage applications wastewater cannot be reused in any sanitary processing, it can be reused in other processes to reduce to overall water balance. In most applications, treating wastewater to reverse osmosis quality will in all likelihood generate a higher quality water that what comes from the processing plant’s raw water supply. This water can be used to feed boilers, sent to a cooling tower as makeup water, among others.
Food and Beverage wastewater generally has a very high organic loading which makes it an ideal candidate for anaerobic digestion. The main byproduct of anaerobic digestion is biogas which consists of approximately 65% methane. This methane can be harnessed and sent to a generator as fuel to generate both heat and electricity, which is integrated into the main plant.
See the Grassland Dairy presentation (link to case study page) to learn how their facility is able to generate enough electricity to power 2,500 homes per year and save over $20,000 per month in electricity costs.
One of the most challenging operating costs of a wastewater treatment plant is the biosolids (sludge) handling process. Biological processes generate a large volume of biosolids that must be processed and disposed of. Typical applications for disposing of sludge are land spreading on agricultural fields and disposing of them in landfills.
Biosolids that can be thickened on site have a direct impact on the volume of sludge that can be hauled thereby reducing the producer’s expense and liability.
With the uncertainty of land spreading sludge in Wisconsin and other states different sludge management methods are open for consideration. Northern climates also necessitate other means of sludge management as the fields are frozen or snow covered. Simple storage is the most common practice with other options outlined below.
CFR manages biosolids using three base techniques, with other options available depending on the project specifics:
- Membrane concentration: Using the crossflow membranes biological sludge from an activated sludge process may be thickened from approximately 1 wt% up to and greater than 3 wt%. This may not seem like much, but represents a 67% decrease in the sludge volume for disposal. As an added benefit the permeate may be directly discharged as the quality is generally equal to or better than the final plant effluent.
- Biological sludge from a food and beverage plant is typically difficult to mechanically dewater and standard equipment requires specific modification. CFR offers two proven technologies, a screw press and centrifuge, to achieve the desired goals. The screw press may achieve 12 wt% to 15 wt% solids and the centrifuge can consistently achieve 18 wt% to 23 wt%, or greater.
- If concentrating via a centrifuge or storage are insufficient then drying is the final step for ultimate disposal. A dryer may use plant waste heat to achieve 90 wt% solids or greater. The dry solids may be more stored, used as animal feed or animal bedding.