A large particle board manufacturer in western Oregon, US, was facing high levels of Total Suspended Solids (TSS) in their effluent.

Their TSS primarily consisted of sawdust and ¼” (6 mm) wood chips, and they had three outfalls covered under a single National Pollutant Discharge Elimination System (NPDES) permit that had the potential to become an expensive environmental violation if excessive TSS was not removed before outfall.

Their existing sedimentation tank was divided into stages with fabric baffle weirs.

After sedimentation flows were sent to a pea gravel filter bed to remove solids prior to outfall, but rain events and growing demand were straining their capacity.

Excessive solids loading during plant washdown had the potential to limit the effectiveness of their sedimentation system. This system relies on gravity, the weir walls, and detention time to remove TSS prior to flows entering their pea gravel filtration system.

The plant manager understood that a big storm event, combined with plant washdown, could overwhelm this critical system.

The plant needed a more effective TSS removal system that could handle larger loads, reduce required detention time for settling, protect their sedimentation system, and reduce the frequency of required cleaning.

Hydro International was contacted to install a demonstration Hydro-Industrial MicroScreen™ unit on site and test performance under the wide variety of operating conditions they encounter.

Various flow rates were tested, with and without prior polymer addition, and during plant washdown.

Grab samples of influent going into and effluent coming out of the Hydro-Industrial MicroScreen™ were analyzed by the plant’s on-site laboratory staff.

Despite the wide variety of their operating conditions, the Hydro-Industrial MicroScreen™ delivered consistently high performance: 77% TSS removal, on average, under all operating conditions. Additionally, solids output from the system were visibly dry.

Solids were 25% total solids (TS) on average, which allowed them to be fed back into the plant process, allowing the manufacturer to reclaim these solids rather than paying to send them to landfill.