The recycling and reuse of industrial wastewater is challenging due to wastewater variability and shifting manufacturing conditions. While older technologies for fine-particle filtration, such as cartridge filters and bag filters, can mechanically achieve the required degree of filtration, they tend to have prohibitive operational costs. This is typically due to the need for frequent filter changes.
At a meat processing plant in Kansas, spikes in high-solids meat particles were clogging up bag filters on a daily basis, reducing output and uptime in the plant’s on-site industrial wastewater treatment plant. The processor needed a solution that reduced the frequency of bag-filter changes and decreased maintenance expenses, while improving the sustainability of operations.
The user had installed an on-site industrial wastewater treatment plant to achieve two goals: 1) to consistently achieve the pre-treatment limits for high-solids water from the local municipal wastewater treatment facility, and 2) to have a sustainable, cost-effective solution for achieving its water reuse and recycling goals.
However, after the treatment plant was operational, the user started seeing a high spike in total suspended solids (TSS) on a daily basis, reducing output and uptime. High levels of solids carried over from the dissolved air flotation (DAF) unit to the 200-micron bag filters were requiring bag changes every 10 minutes.
Solution possibilities
A possible solution was to install lower-maintenance fine-particle filters capable of TSS levels up to 10,000 mg/L and thereby reduce high maintenance cycles. In fact, after learning about fine particle filters, the customer decided to put one to the test, evaluating its ability to remove high-solids meat particles. In the pilot test, a slip stream duplicating typical operating conditions was provided to a TEQUATIC PLUS F-50 filter fitted with a 30-micron filter, including a total filtrate flow of 12 gpm and a cleaning assembly rotational speed of approximately 350 rpm.
Test results are shown in Table 1. The filter removed 97.9 percent of the particles above 20 microns according to an independent laboratory – exceeding the 30-micron design. This clearly demonstrates a high tolerance to variable wastewater, prompting the customer to install a full-scale production skid that has a flow rate of about 120 gpm for 2,000 mg/L TSS water. The skid easily integrated into the existing system, located downstream from the DAF unit.
High-solids feed-water flows through a coarse strainer to the DAF, then to the filter to remove difficult, high-solids particles. This reduces the particle load on the downstream bag filter and a proprietary microfiltration system by Kemco Systems, Inc.
The filter is decreasing the number of bag changes by more than 80%, from every 10 minutes to about every 60 minutes – reducing maintenance and replacement costs. Also, by taking the load off downstream assets, the filter helps improve overall filtrate flow – further enhancing uptime. Initially, for example, the filtrate flow of the proprietary downstream filter would decrease by 70-80 percent, but with the TEQUATIC PLUS filter, it only decreased by 20-30 percent of its initial flow.
In addition to helping the customer reduce consumables and maintenance costs, the filter is delivering a water recovery greater than 99%. Due to continuous, cross-flow filtration, it requires no backwash cycles.
Using the filter also gives the customer an opportunity to avoid additional capital expenses. Because the filter can remove such a high percentage of solids above 20 microns, the user is able to further optimize the filter train by increasing the flow rate through the DAF without worrying about the higher water flow carrying the solids through the system. Consequently, the user minimizes the need for additional capital investment when a higher throughput is needed.
Snappy results
The fine-particle filter combines the power of continuously cleaning, cross-flow filtration with centrifugal separation and solids collection in one simple device. The solution is designed to process a wide range of difficult, high-solids feed waters up to 10,000 mg/L and greater. It is said by Dow to offer a cost-effective, reliable solution to traditional filtration technologies, facilitating high uptime, consistent performance and a small footprint, including less disposal, higher water recovery and less space.
In summary, the filter solves the high solids issue by reducing total suspended solids (TSS) by nearly 98% for meat particles greater than 20 microns, while conserving water resources. The user experiences more uptime and lower expenses through an 80 percent reduction in bag filter changes; improved stability of downstream filtrate flow; avoidance of additional capital expenses; >99 percent water recovery; and no backwash.
Dow Chemical Co. says it connects chemistry, innovation and awareness of the need for sustainability, to address challenges in clean water, renewable energy and increasing productivity.
Visit www.cleanfiltration.com or www.dowwaterandprocess.com.
