Summary of treatment practices used in stormwater harvest and use systems

Summary of treatment practices used in stormwater harvest and use systems
Link to this table

Treatment Method	Primary Purpose	Location in System
Pre-storage and in-storage treatment
Filtration/Biofiltration	Reduce particulates and nutrients	Before storage
Grassed Swale	Reduce particulates	Before sedimentation
Leaf Screens and Strainers1	Remove organic solids	Gutters and downspouts (before sedimentation)
Vortex Filters	Remove organic and gross solids, particulates and debris down to 280 microns.	Before storage and connected to smoothing inlet in tank.
Screens	Reduce gross solids	Before sedimentation
Settling Basin/Sedimentation1	Remove particulates	Before or during storage
Smoothing Inlet	Prevents the resuspension of settled solids and introduces oxygen to the tank to enhance aerobic conditions	In tank
Floating Filter	Filter particulates before water enters a submersible pump (protects pump)	In tank
Skimming Overflow Siphon and Trap	Remove floating debris, (e.g. pollen) and creates a water trap to prevent animals and downstream odors from entering the tank.	In tank
Aeration Unit	Used to introduce oxygen to tank which aids in the formation of aerobic beneficial bacteria that have been shown to reduce nutrient and metals concentrations.	In tank or can be set up in a venture injection application.
Post-storage treatment
Activated Charcoal1	Remove chlorine, reduce odor, remove organics	After sediment filtration, before use and before or after UV filter
Boiling/distilling1	Kill microorganisms	Before use
Chemical treatments (chlorine) 1, a	Kill microorganisms	During storage or at distribution. Most commonly injected post filtration at point of distribution or in day tank. Should not be required in tank if adequate prefiltration is implemented
Electrodialysis2	Remove dissolved ions (salts)	Between storage and end use Not required in rainwater systems
In-line filters	Removes sediment, reduces turbidity, increases ultraviolet treatment	Between storage and end use and prior to UV treatment. Recommend 1 micron to meet current indoor water quality criteria of less than 1 ntu or sample the water and send to the UV manufacturer.
Microfiltration2	Remove suspended solids and microorganisms	Between storage and end use
Ultrafiltration	Remove suspended solids,organics	Between storage and end use
Nano-filtration2	Remove multivalent ions, organics microorganisms, viruses and proteins	Between storage and end use
Reverse Osmosis2	Remove monovalent ions, organics, microorganisms and viruses. May remove beneficial nutrients and produce highly corrosive water that needs to be reconditioned.	Between storage and end use
Sand filtration		Between storage and end use
Ozonizationb	Inactivate microorganisms	Before use typically applied through a venture and injected into the tank or a smaller contact tank.
Ultraviolet Disinfectionb	Inactivate microorganisms	Before use

¹Georgia DCA, 2009
²Met Council, 2011
^aBefore activated charcoal (if included)
^bAfter activated charcoal (if included). Refer to specific UV and carbon filter manufacturer for guidance,br> ³ VA Rainwater Harvesting Manual, Cabell Brand center, 2009