Industrial Water Reuse - Wood Products Industry

Wood products manufacturing facilities who want to recycle their process wastewater will face one major challenge. They need to obtain a reuse water quality that protects their important and expensive process equipment.

Excess saps and tars from processing southern yellow pine, for example, will gum up WESPs, Centrifuges, Pumps, and RTO Media units. This can mean costly and time consuming down time to replace them. If the wrong treatment program is implemented or the wastewater is reused without treatment, it could mean as much as a million dollars to replace the RTO media alone each time it becomes fouled. Plant maintenance costs also rise from the maintenance, labor, parts replacement, hydro blasting, and waste disposal. Additionally, when all the maintenance is taking place, the plant has to be shut down.

With the right treatment program that is designed to protect this valuable equipment, it could last a decade or longer before requiring replacement, instead of replacing it every couple years. Here is a real world example from a wood products company in Georgia:

The facility was reusing their process water but incurring high costs associated with maintaining their process equipment:

• RTO media replacement every 2 to 3 years, costing them $1 million each time.
• Once per month, the plant had to shut down production to clean the equipment, taking about 70 man hours each time.
• During downtime, they were having to store wastewater on site and received non-compliance violation notices for it.
• Their centrifuges were generating 100 tons or more of 80%+ moisture solids that they had to dispose.

The culprit was the excess tars, saps, tannins, and lignins in their wastewater that left deposits in the WESPs, RTOs, and centrifuges when they reused it.

To resolve this issue, the facility hired a wastewater treatment company who installed a new wastewater treatment system that utilized a custom tailored chemical treatment program to remove the TSS, tars, and saps while reducing the TDS in the recycle tank water. This provided the facility with cleaner water in the recycle tank and clean WESP flush water. Additionally, a treatment program was provided for the shutdown water, which enabled the facility to treat and discharge that water within the discharge permit limits.

After the new process was implemented, the facility has practically eliminated the high costs and maintenance activities they were experiencing before:

• Eliminated the need to haul off water due to inefficient solids removal from the centrifuges.
• Eliminated the need to store water onsite and thus no more compliance issues.
• Eliminated the need to replace RTO media (it’s now been over 9 years since this system was implemented, and the RTOs have not been replaced since).
• Reduced costs and manpower required for routine planned maintenance by 80%.
• Eliminated need for off-site hydro blasting to clean up the WESP and associated piping (all the systems can now be cleaned on site).
• Solid waste generation reduced by 60-70% by increasing solids in filter cake. The filter cake is now 40-50% moisture (as compared to the previous 80%+)
• The filter cake is 7,000 – 10,000 BTU/lb, which creates a potential fuel blending source from a product of their waste stream.

The wood industry can reuse their wastewater successfully as long as the treatment program for the reuse water is designed for their facility with their equipment life as the focus.