Treatment in BMP’s and LID’s for InfoSWMM and ICM SWMM - with Emojis

 Treatment in BMP’s and LID’s

5.1 Treatment

Excerpt from the EPA manual Storm Water Management Model Reference Manual Volume III – Water Quality (PDF) which can be found here

5.1.1 Background

Stormwater Quality Management: BMPs and LID 💧🌿

Stormwater quality is pivotal for urban and environmental health. It's primarily managed through a blend of "best management practices" (BMPs) and a hydrologic source control technique, widely recognized as "low impact development" (LID). The treatment can be at the runoff source or within the conveyance network. While LID's source treatment will be discussed later, this section sheds light on SWMM's modeling of treatment within the conveyance system.

Unit Treatment Processes in Conveyance Systems 🌀: Table 5-1, inspired by Huber et al. (2006), classifies the treatment processes leveraged by various BMPs within conveyance systems. The aspiration is to model these processes fundamentally, correlating pollutant removal with design parameters, hydraulic variables, and chemical properties. However, the current understanding often limits this approach, pushing reliance towards empirical data-driven relationships.

Challenges with Monitoring Data 📊: Strecker et al. (2001) highlight the intricacies of using monitoring data to draw consistent BMP effectiveness conclusions. The International Stormwater BMP Database (www.bmpdatabase.org) emerges as a robust resource, offering BMP performance data from 500+ studies across 17 BMP and LID categories. This database is a living entity, continually updated with fresh data.

BMP Performance Overview 🌱: Table 5-2 showcases the median influent and effluent event mean concentrations (EMCs) across various BMP categories and pollutants, as extracted from the BMP database. The yellow-highlighted cells signify significant pollutant removal by the respective BMP category. Meanwhile, Table 5-3 provides a snapshot of median removal percentages of common pollutants by filtration, ponds, and wetlands, as documented in the Minnesota Stormwater Manual. These percentages align with the median EMC figures from Table 5-2.

In Summary 📝: 

Stormwater quality management, through BMPs and LID, is vital. While comprehensive modeling remains a challenge, resources like the BMP Database offer invaluable empirical insights. Leveraging this data can aid in enhancing stormwater treatment, safeguarding both urban landscapes and natural ecosystems. 🌍💧🌳.ntages are consistent with those inferred from median EMC numbers in the BMP database table 5-2.

Table 5-1 Treatment processes used by various types of BMPs

Process	Definition	Example BMPs
Sedimentation	Gravitational settling of suspended particles from the water column.	Ponds, wetlands, vaults, and tanks.
Flotation	Separation of particulates with a specific gravity less than water (e.g., trash, oil and grease).	Oil-water separators, density separators, dissolved-air flotation.
Filtration	Removal of particulates by passing water through a porous medium like sand, gravel, soil, etc.	Sand filters, screens, and bar racks.
Infiltration	Allowing captured runoff to infiltrate into the ground reducing both runoff volume and loadings of particulates and dissolved nutrients and heavy metals.	Infiltration basins, ponds, and constructed wetlands.
Adsorption	Binding of contaminants to clay particles, vegetation or certain filter media.	Infiltration systems, sand filters with iron oxide, constructed wetlands.
Biological Uptake and Conversion	Uptake of nutrients by aquatic plants and microorganisms; conversion of organics to less harmful compounds by bacteria and other organisms.	Ponds and wetlands.
Chemical Treatment	Chemicals used to promote settling and filtration. Disinfectants used to treat combined sewer overflows.	Ponds, wetlands, rapid mixing devices.
Natural Degradation (volatilization, hydrolysis, photolysis)	Chemical decomposition or conversion to a gaseous state by natural processes.	Ponds and wetlands.
Hydrodynamic Separation	Uses the physics of flowing water to create a swirling vortex to remove both settleable particulates and floatables.	Swirl concentrators, secondary current devices, oil-water separators.

Table 5-2 Median inlet and outlet EMCs for selected stormwater treatment practices

Pollutant	Media Filtration		Detention Basin		Retention Pond		Wetland Basin		Manufactured Device
	In	Out	In	Out	In	Out	In	Out	In	Out
TSS mg/L	52.7	8.7	66.8	24.2	70.7	13.5	20.4	9.06	34.5	18.4
F. Coliform, #/100mL	1350	542	1480	1030	1920	707	13000	6140	2210	2750
Cadmium, ug/L	0.31	0.16	0.39	0.31	0.49	0.23	0.31	0.18	0.40	0.28
Chromium, ug/L	2.02	1.02	5.02	2.97	4.09	1.36			3.66	2.82
Copper, ug/L	11.28	6.01	10.62	5.67	9.57	4.99	5.61	3.57	13.42	10.16
Lead, ug/L	10.5	1.69	6.08	3.10	8.48	2.76	2.03	1.21	8.24	4.63
Nickel, ug/L	3.51	2.20	5.64	3.35	4.46	2.19			3.84	4.51
Zinc, ug/L	77.3	17.9	70.0	17.9	53.6	21.2	48.0	22.0	87.7	58.5
Total P, mg/L	0.18	0.09	0.28	0.22	0.30	0.13	0.13	0.08	0.19	0.12
Orthophosphate, mg/L	0.05	0.03	0.53	0.39	0.10	0.04	0.04	0.02	0.21	0.10
Total N, mg/L	1.06	0.82	1.40	2.37	1.83	1.28	1.14	1.19	2.27	2.22
TKN, mg/L	0.96	0.57	1.49	1.61	1.28	1.05	0.95	1.01	1.59	1.48
NOX, mg/L	0.33	0.51	0.55	0.36	0.43	0.18	0.24	0.08	0.41	0.41

Source: International Stormwater BMP Database, “International Stormwater Best Management Practices (BMP) Database Pollutant Category Summary Statistical Addendum: TSS, Bacteria, Nutrients, and Metals”, July 2012 (www.bmpdatabase.org).

Table 5-3 Median pollutant removal percentages for select stormwater BMPs

Pollutant	Sand Filter	Ponds	Wetlands
Total Suspended Solids	85	84	73
Total Phosphorus	77	50	38
Particulate Phosphorus	91	91	69
Dissolved Phosphorus	60	0	0
Total Nitrogen	35	30	30
Zinc and Copper	50	70	70
Bacteria	80	60	60

Source: Minnesota Stormwater Manual (http://stormwater.pca.state.mn.us).