Manufacturing and industrial operations contribute to a community’s revenue stream when their process wastewater is sent to municipal wastewater treatment facilities. Manufacturers need to dispose of their excess water, and municipalities are the ones that can take it away. This relationship often comes at the manufacturer’s expense. But what if the municipal system is already reaching its flow or loading capacity?
Municipalities have to look elsewhere when their wastewater treatment facilities are at or near capacity and expansion or replacement of the facility isn’t in the cards. One place wastewater can be reduced is through a municipality’s manufacturing and industrial customers.
To help these customers reduce their wastewater discharges, and save money in the process, refer them to the familiar phrase: “reduce, reuse, recycle,” and how about re-sell? Below we examine just how these four Rs, coupled with a better understanding of their processes, can get your customers on the path toward wastewater reduction.
Reducing the amount of wastewater a facility generates seems like an obvious place to start. But, for many of your customers, that’s easier said than done. There are a number of ways you can help industrial manufacturers optimize their wastewater flows. A food processing plant, for example, generates wastewater throughout the day. But during product changeover or sanitation cycles, wastewater volume and wastewater characteristics can change quickly.
In fact, during sanitation, a facility may discharge up to 80 percent of its daily wastewater flow in a four- to six-hour period. Wastewater characteristics like organic strength, temperature, acidity and toxicity also change. Downstream technologies (such as flow equalization, pH adjustment and pretreatment) can help mitigate these conditions. But manufacturers often avoid these mitigation measures because they can be costly and consume their profit margins. However, by doing some, they’ll likely save on water treatment charges.
In addition, many plants develop contaminants during their manufacturing process which have to be removed and processed onsite.
Manufacturers can help reduce wastewater by looking upstream. By implementing a pretreatment process, industrial clients can effectively reduce the amount of wastewater they discharge at the end. This saves dollars in the long run, and benefits the city. In some processes, contaminants have to be removed from the wastewater prior to treatment. This is often done by segregating the contaminants before they reach the municipal wastewater treatment facility. They can also identify ways to reduce wastewater flows by optimizing clean-in-place programs.
Manufacturers working with their quality assurance/quality control team, machine operators, control logic programmers and process equipment suppliers can be an effective way to determine precise requirements for sanitation processes. This can also help reduce overall flow processed by municipalities. Once manufacturers have developed standard processes, they can use automated sensors and controls to lock down procedures, ultimately taking the guesswork out of the process.
Does your manufacturing and industrial customers’ process wastewater exhibit periods of relatively low organic or chemical impacts? If a manufacturing facility has non-critical operations, they may be able to safely capture the process wastewater for reuse. In fact, a plant’s final sanitation rinse can be suitable to use as a first flush during product changeover or sanitation.
If it can’t be used in the sanitation process, can it be used elsewhere in the facility? Some processors reuse low strength wastewater as floor wash down. And if it’s clean enough, manufacturers should consider whether bypass of on-site pretreatment, discharge to final effluent, or direct discharge to the municipality is feasible.
If reuse isn’t an option, what about reselling?
But there may be another way. Sometimes a wastewater treatment process at a manufacturing facility may generate a byproduct that can be sold. By thinking outside the box, manufacturers can isolate elements from their wastewater process like precious metals, chemicals and even the water itself, then resell it. It’s an innovative way of thinking—but there is a market for metals, particularly those with high purity cathodes recovered from the wastewater treatment process.
Similarly to how metals and chemicals can be isolated from a wastewater stream and sold, they can also be put back to work for the manufacturer. These cases may be rare but, in instances where the industrial process also requires metals and chemicals, recycling them can lead toward a “zero discharge” process—one of the most heralded situations in manufacturing.
Since most water discharged from industrial processes is not cleaned enough to be sold as potable water, manufacturing clients might still be able to reuse it in a similar manner. Recycled water can often be used for irrigation purposes. This recycled water can be used to help irrigate farmer fields, or even the facilities own landscaping.
Using data for better understanding of process wastewater can lead to lower discharge
Because process wastewater composition is highly variable, your manufacturing and industrial customers can better understand their process wastewater by gathering data at various times and locations. But how do they get the data? They can install temporary flow meters and selective samplers to collect wastewater from primary points of generation within their facility. They should consider sampling discharge lines from processing machines or waste collection pits to track flow volume and waste strength trends.
They can also review changes in their wastewater composition over time. If the data warrants, your manufacturing and industrial customers should evaluate options to retrofit their system in order to segregate the highest strength waste for alternate management or disposal. Recent studies completed at beverage bottling operations have shown that approximately 60 percent of the biochemical oxygen demand (BOD) can be captured in the first 90 seconds of a system flush.
This is important because a relatively small volume of captured wastewater will contain a majority of the waste strength, potentially translating into a reduced or focused 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.
If your municipality is at capacity for wastewater flows or nutrients and you can’t retrofit your system or build a new one, the key to reducing and ultimately saving just might be in turning to your manufacturing and industrial customers. By working with these customers, you can help them reduce their wastewater flows. Reduced flows not only means less wear and tear on your city’s wastewater system, but a longer lasting facility.
Dan Schaefer, PE*, is a senior wastewater engineer and is dedicated to helping cities make the most of their wastewater infrastructure. Contact Dan