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Case Study

Dry Land Sort Runoff

An integral part of forestry operations is the sorting and grading of logs. Up to about twenty years ago, this largely happened in water, but environmental concerns have moved this operation onto dry land. However this has created its own new problems, such as the production of toxic run-off caused mainly by rainfall, but also from water used on site. Dry Land Sort (DLS) run-off is known to be toxic to fish. This toxicity may arise from dissolved organics (e.g. fatty and resin acids), fine particles and even dissolved metals (e.g. barium, zinc).

In 2000, Microbial Technologies began working with two DLS operators to develop biological treatment systems for their runoff. The major problem in developing these systems was the very restricted amount of space available, combined with the intermittent nature and large volumes of runoff produced in a very short time. Another issue is the requirement for very simple operation.

A breakthrough in our laboratory investigations lead to the development of a simple, economical treatment process, loosely based on the concept of vertical flow wetlands. Metals and other toxic constituents are entirely removed, and the treated effluent is rendered non-toxic in conventional (D. magna, rainbow trout) toxicity tests. This is significant because other researchers have so far only partially removed toxicity.

Pilot-scale facilities were installed in 2000, followed by full-scale facilities, to our knowledge the first in North America. After over one year of operation, our systems have performed reliably despite wide ranges of flows and loadings. Fish and seals are returning to the adjacent foreshore, a sure sign that the environment is recovering. This is the gratifying reward for helping industry tackle and resolve a difficult environmental problem.