| Summary: | Runoff generated from forestry dry land sort (DLS) operations contains materials
from logs, chip piles, and industrial machinery and poses an environmental threat to
receiving waters due to its high suspended particle loads, potentially high metals
concentration, and frequent toxicity. Since there is currently no legislation or discharge
regulations specific to DLS runoff (as for pulp and paper effluents), polluting DLS
operations have largely gone unnoticed and as a result few treatment technologies have
been tested. In this study, twelve samples of DLS runoff were taken from three dry land
sorts located on the Sunshine Coast of British Columbia. Samples had chemical
oxygen demand (COD) ranging from 346 mg/L to 3690 mg/L (of twelve samples tested),
pH and metals (of two samples tested) that did not comply with British Columbia (BC)
Approved Water Quality Guidelines and the BC Municipal Sewage Regulations. The
particles of two samples were characterized chemically and morphologically and it was
determined that fresh DLS runoff contains highly aggregated inorganic and organic
colloidal particles ranging from 1 to 10 pm in size. Although some of these particles
sedimented during storage at 4 °C or 25 °C, most particles remained relatively stable in
suspension suggesting the requirement for filtration or a secondary treatment process.
An oxide-coated sand filtration process performed well over three series of'
column experiments, removing up to 86% of the COD and 92% of the turbidity, when
operated as a re-circulating filter for 24 hours. Batch adsorption experiments using the
oxide-coated sand removed averages of 17% and 26% DLS runoff COD over two series
of experiments. The same sand, however with the oxide-coating stripped (oxidestripped
sand), failed to remove COD from solution in batch adsorption experiments
suggesting that the oxide-coating enhanced absorption of suspended particles. When
oxide-stripped sand filters were run in parallel with oxide-coated sand filters treating
successive batches of DLS runoff, the oxide-stripped sand treated on average 34% less
COD and 32% less turbidity. Neither flocculation nor biological activity was determined
to be an important mechanism to the sand filtration process over successive batch
treatment runs. === Applied Science, Faculty of === Chemical and Biological Engineering, Department of === Graduate
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