BCR’s Glossary of Acronyms & Technical Terms

Biosolids Also known as ‘Sludge’, this term refers to the solid waste byproduct of the sewage treatment process. The liquid byproduct is ‘Effluent’.
BOD Biochemical Oxygen Demand.
The amount of dissolved oxygen needed by aerobic biological organisms in a body of water to break down organic material. Used as an indication of the organic quality of water, and of the effectiveness of wastewater treatment plants.
DEQ Department of Environmental Quality.
Oregon’s state agency tasked with ensuring Clean Water Act compliance. Molalla STP permits are handled by DEQ’s Northwest Region office, at the CH2M Hill building (2020 SW 4th Avenue, Suite 400, in Portland). DEQ uses the term ‘Recycled Water’ when referring to treated wastewater.
DMR Discharge Monitoring Report.
A monthly report required in accordance with NPDES, in which Molalla STP submits data tracking daily water quality. It includes parameters such as inflow, outflow, pH, biochemical oxygen demand (BOD), total suspended solids (TSS), nutrients (nitrates and phosphorus), various toxic pollutants, temperature, etc.
Effluent Also known as ‘Wastewater’, this term refers to the liquid waste byproduct of the sewage treatment process. The solid byproduct is ‘Biosolids’.
I/I Infiltration/Inflow.
Both terms refer to the invasion of extra and unwanted water into the raw sewage flow. Infiltration is water that leaks via poor pipe seals or pipe fractures. Inflow is the addition of rainwater and other liquids that is improperly piped into the sewer lines. An ‘I and I Analysis’ is done to assess the quality of a sewer system in terms of leakage.
Influent Also known as raw sewage, referring to the mixture flowing into a Sewage Treatment Plant. In a well-maintained sewer system, a minimal amount of liquid water is included; in a poorly maintained system, rainwater and other leakage increases the water content, causes a much higher inflow, and creates larger and more expensive treatment demands. See also ‘I/I’.
NPDES National Pollutant Discharge Elimination System.
A system managed by the U.S. EPA, to ensure proper management and handling of pollutants so that water quality is protected. An NPDES permit is required before wastewater can be discharged into Bear Creek or the Molalla River.
STP Sewage Treatment Plant.
Typically consists of a series of ponds for the holding of raw sewage, to allow primary treatment (floating of oils and later components, and settling-out of heavier solids. This is followed by Secondary Treatment () and Tertiary Treatment ().
TSS Total suspended solids.
A measure of water quality, obtained by filtering a water sample and then weighing the dried residue extracted during the filtration.
WPCF Water Pollution Control Facility.
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