week 5 - stormwater design Flashcards
describe the result of locally drained impervious surfaces into storm water pipes
larger peak flows
faster flows
suspended load and sediment
dissolved contamination
gross pollutants
what are secondary treatment for gross pollutants
swales, infiltration areas and trenches, porous paving, bio retention systems and rain gardens
what are the 3 types of gross pollutants
organics, products and mineral sediment.
what are primary treatment for gross pollutants
grassed swales or litter traps.
what are tertiary treatment for gross pollutants
enhanced sedimentation and filtration, biological uptake, adsorption onto sediments by using wetlands or bio retention systems.
what does know your catchment refer to
using a top down approach such as using gross pollutant traps before constructed wetlands. if you dont have gross pollutants such as minerals before the wetland, the performance can be hindered
when are vegetated waterways useful
in low gradient catchments
describe charactertistcs of the trash rack
they are used within a pit
needs regular maintenance
some have chemical or physical filtration
what is a GPT and examples
gross pollutant trap
End of pipe bags:
used at the end of a stormwater drain where a metal bag captures GP.
nicholas ski jump: high flow can by pass the screen filter but are really useful for fine particles and can store dry pollutants
baramy drop rack trap: intercepts and dry stores sediment, trash and other debris.
wet sump: by passes water leaving pollutants behind in the sump. they can trap hydrocarbons and solids and removed by vacuum.
Litter dam: floating litter booms capture floating pollutants and some hydrocarbons.
characteristics of constructed wetlands
can improve water quality parameters such as N, P, DO, suspended load etc.
small basins can be scoured out in large floods
needs constant maintenance
not cheap
