cive230 lec 12 - methods to improve water quality

three methods to sustainably mitigate human influences on waterways

• reduce quantity of runoff (from the source and in transport)

• Reduce the amount of pollution entering water cycles: along the ground, in natural water bodies, in the atmosphere

• Apply engineering methods to mitigate the impacts

Engineering Methods to Increase the Sustainability of Water Resources

• Reducing the quantity of runoff

• Employing natural sedimentation methods

• Increasing sedimentation rates

• Applying advanced methods (chemical, biochemical, organic) for water treatment.

factors that affect runoff

area, rainfall intensity, characteristics over which the runoff occurs (slope, permeability, etc.)

reducing runoff

• Avoid the conversion of permeable to impervious surfaces

• Maintain naturalized areas

• Increase density of development

• Utilize permeable building materials and techniques

low impact development (LID)

n approach to land development that works with nature to manage stormwater runoff by mimicking natural water processes - prioritize infiltration, evapotranspiration, and storage of rainwater at its source

Preventing pollutants from entering waterways

• eliminate combined sewer systems

• regulation - total maximum daily load (TMDL) standards

• mitigate first flush concerns

• pollution credits trading

first flush

the initial runoff from a rainstorm, particularly in urban areas, which contains a higher concentration of pollutants compared to the rest of the storm's runoff (~90% pollutants in first 15 minutes)

factors that influence severity of first flush

• duration between precipitation events

• magnitude of pollution occurring in catchment area

• the natural cleansing ability of the catchment area

sedimentation method

as velocity of water flow decreases, flow times increase and settling increases

sedimentation areas

• channels, through the use of stone and other speed reducing materials

• Natural wetlands

• Detention (short term) basins

• Retention (longer term) basins

• Sedimentation ponds (overflow designs)

advanced engineering methods

• Chlorinization – use of chlorine compounds to destroy pathogens

• Ozone which destroys the cell walls of pathogens

• UV treatments

• Bioremediation: Phytostabilization (the use of plant materials to stabilize toxins and metals), Phytoremediation (the sorption of toxins and metals into plant materials (ferns/radishes) which can then be removed), Rhizofiltration (the use of plant roots to remove metals)