By getting creative, municipal wastewater treatment facilities (WWTFs) and their large, water-intensive customers can work together to send less process wastewater to municipal sewers for treatment. Customers can save money by using and discharging less water, and municipalities can avoid expensive infrastructure upgrades.
Manufacturing and industrial customers that send large amounts of process wastewater to municipal sewers also add a lot of money to community’s revenue stream each time they pay their water treatment bill.
In general, this process is win-win: the manufacturer’s wastewater needs to be treated before being reintroduced to the environment, and the municipality generates revenue because its WWTF can do just that.
But sometimes sending less process wastewater to a municipality’s WWTF is a good idea – for both the manufacturer and the municipality. The manufacturer could reduce its operational costs by producing less wastewater. And what if the WWTF is nearing capacity for flow or nutrients but a costly expansion or replacement of the facilities simply isn’t in the cards?
To reduce manufacturing and industrial wastewater discharges and save money in the process, let’s start with the familiar phrase “reduce, reuse, recycle” and break the rules just a bit by adding the non “R” word “sell.” Below, we examine just how these three Rs and one S can help municipalities and their customers reduce the volume of process wastewater flowing into WWTFs.
Generating less wastewater may seem like an obvious place to start, yet for many industries it’s easier said than done. Putting an optimization program in place can help industrial manufacturers manage their wastewater flows.
A food processing plant, for example, generates wastewater throughout the day. But at certain times – like during product changeover or a sanitation cycle – the wastewater volume can increase quickly, and the characteristics of wastewater can change quickly.
Let’s look at sanitation. During a 4-6 hour sanitation cycle, a facility may discharge up to 80% of its daily wastewater flow. Wastewater characteristics also change, such as organic strength, nutrient loading, temperature, pH and toxicity. Pretreatment technologies like flow equalization and chemical/physical pretreatment are required to help mitigate these conditions, but these mitigation measures can be costly and consume a company’s profit margins. Investigating ways to reduce volumes that require pretreatment can help these large customers save on wastewater treatment charges.
In some cases, contaminants must be removed from the wastewater prior to treatment. This can be done by segregating the contaminants before they reach the municipal WWTF. Optimizing a clean-in-place program is another way a customer can reduce wastewater flows.
By looking upstream and implementing a pretreatment process, manufacturing and industrial customers can effectively reduce the amount of wastewater they discharge into a municipal sewer. This saves dollars in the long run and benefits the municipality.
A manufacturer can work with their quality assurance/quality control team, machine operators, control logic programmers and process equipment suppliers to determine precise requirements for sanitation and help reduce overall flow processed by municipalities. Once a manufacturer has developed a standardized process, they can use automated sensors and controls to lock down procedures, ultimately taking the guesswork out of the process.
A manufacturer may be able to safely capture process wastewater for reuse if it exhibits periods of relatively low organic or chemical impacts, or if the facility has non-critical operations. Another option: a plant’s final sanitation rinse may be suitable to use as a first flush during product changeover or sanitation.
If a final sanitation rinse can’t be used in the sanitation process, can it be used elsewhere in the facility? Some processors reuse low strength wastewater as floor washdown. And if it’s clean enough, manufacturers could consider if it’s feasible to bypass on-site pretreatment, discharge to final effluent, or direct discharge to the municipality.
Sometimes a wastewater treatment process at a manufacturing facility may generate a byproduct that can be sold. By thinking outside the box, innovative manufacturers can isolate elements from their wastewater process – think precious metals, chemicals and even the water itself – then sell it. There is a market for metals, particularly those with high purity cathodes recovered from the wastewater treatment process.
When metals and chemicals are isolated from a wastewater stream, they can be sold, as mentioned above, or they can be put back to work for the manufacturer. These cases may be rare. But when metals and chemicals are required for the industrial process, recycling them can lead toward “zero discharge,” one of the most heralded situations in manufacturing.
Most water discharged from industrial processes is not cleaned enough to be sold as potable water, yet manufacturers might still be able to reuse it in a similar manner. Recycled water can may be used to irrigate agricultural fields or even manufacturer’s own landscaping.
Manufacturing and industrial customers can better understand the variable composition of process wastewater by gathering data at various times and locations. How to get the data? By installing temporary flow meters and selective samplers to collect wastewater from primary points of generation within the facility. Also consider sampling discharge lines from processing machines or waste collection pits to track flow volume and waste strength trends.
Wastewater composition also changes over time. If the data warrants, manufacturing and industrial customers could evaluate options to retrofit their system to segregate the highest strength waste for alternate management or disposal. Recent studies conducted at beverage bottling operations show that approximately 60% of the biochemical oxygen demand can be captured in the first 90 seconds of a system flush.
When a relatively small volume of captured wastewater contains most of the waste strength, it’s possible to reduce or better focus a capital investment for wastewater treatment. Treating a smaller volume of concentrated wastewater is often better for cities and manufacturers than treating a large volume of low-strength wastewater.
Related Content: 7 Signs Your Wastewater Facility Needs a Condition Assessment
Reducing the volume of process wastewater can benefit manufacturing and industrial customers as well as municipal WWTFs that are at capacity for wastewater flows or nutrients when retrofitting the system or building a new one isn’t an option. Working together to reduce flows can help lower a business’s operational costs while helping a municipal WWTF last longer.
Dan Schaefer, PE* is a senior wastewater engineer dedicated to helping municipalities and industrial dischargers alike make the most of their wastewater infrastructure. Contact Dan