ECOSOL DROP TRAP

WATER SENSITIVE URBAN DESIGN & CONSTRUCTED WETLANDS

AT-SOURCE (TOP ENTRY OR IN-LINE) PRIMARY TREATMENT SOLUTION

The Ecosol Drop Trap is designed to remove and retain solid pollutants conveyed in stormwater runoff from impervious surfaces. The top entry filtration system consists of a pre-cast concrete pit containing a capture basket and overflow by-pass flaps. The unit is typically installed as a top entry system however can also be adapted to either in-line, or at the end of the stormwater line, where there is a drop between the upstream invert and downstream obvert levels of at least 450mm, and preferably more.

This drop is needed so that the structure can house an adequately-sized basket. Solid pollutants conveyed in flows from the upstream pipe or overland surface flows are filtered through the basket positioned directly below the upstream pipe invert or grated access cover at surface level. The filtered stormwater then passes through the unit to the downstream outlet pipe and into the drainage network without any head/hydraulic loss through the unit. As the basket approaches 90% full, the by-pass flaps begin to open in response to the incoming flow. Once the basket is 100% full the pressure of the incoming flow forces open the by-pass flaps, allowing the excess flow, to enter the drainage system through the by-pass openings. This effectively eliminates the likelihood of flooding, a common fault with other systems. Even when in by-pass, there is minimal resuspension of settled pollutants.

When the flow ceases, the flaps return to their normal position (see opposite for a graphical representation of the unit in operation). The Ecosol Drop Trap separates, collects, and retains more than 98% of solid pollutants greater than 3mm in size and it traditionally not installed on drainage lines larger than 600mm in diameter.

The Ecosol Drop Trap has many key features and benefits some of which are listed below.

DROP TRAP KEY FEATURES AND BENEFITS

Cost efficient and effective at-source primary treatment solution
Visually unobtrusive, fully self-contained underground system
Easily maintained by crane or vacuum truck
Durable, robust product, engineered for the environment in which it operates

At Ecosol we can site measure, fabricate, install and maintain your Drop Trap making the whole process seamless.

The Ecosol Drop Trap is able to be custom designed to suit most applications and can be supplied complete in its own pre-cast concrete pit or the basket can be retrofitted into existing stormwater junction pits.
The below tables provide a general guide on typical system dimensions for cylindrical pipe applications.

Ecosol DROP TRAP CONFIGURATION & SIZES
Ecosol Drop Trap typical product dimensioning and weights - 2018
Ecosol Product CodePipe DiametersApproximate External Product DimensionsPollutant Storage Capacity3Designed LoadingApproximate Heaviest Lift4
(mm)Length (mm)Width (mm)Depth1 (mm)Drop2 (mm)(m3)ClassTonnes
Ecosol Drop Trap 1200300150015001,9004500.40B - D4.4
3752,1256000.514.8
4502,3507500.665.3
5252,5759000.825.7
6002,80010500.976.2
Ecosl Drop Trap 1500300180018001,9004500.70B - D5.6
3752,1256000.866.0
4502,3507501.126.6
5252,5759001.387.2
6002,8001001.647.7
  1. Depth indicated is the overall external pit depth based on a the nominated drop between the upstream inlet pipe invert level and downstream outlet pipe obvert level inclusive of a 150mm base slab thickness and nominal 1.0m depth to inlet invert.
  2. Drop as shown is the drop indicated between the upstream inlet pipe invert level and downstream outlet pipe obvert level.
  3. Pollutant storage capacities are determined by the available drop in the system.
  4. Weights indicated are an indicative guide only and will vary depending on the depth to inlet invert and the available drop between the inlet and outlet pipes.

The Ecosol Drop Trap is designed to treat 100% of the incoming flow and operates with little impact on the hydraulic performance of the upstream pipe. Utilising the drop between the upstream pipe invert and the downstream pipe obvert to accommodate the capture basket ensures there is no obstruction to the flow through the drainage line of the outlet pipe.

Ecosol DROP TRAP TESTING HYDRAULICS & PERFORMANCE CHARACTERISTICS
Ecosol Drop Trap indicative treatable flow rates and by-pass capacities specific to outlet pipe diameters
Ecosol Product CodeInlet & Outlet Pipe DiametersTreatable Flow Rate1 (L/s)By-pass Capacity2Headloss3Pollutant Storage Capacity
mmGradient 2%Gradient 5%L/smm(m3)
Ecosol Drop Trap 12003001302164002400.40
3752483926003450.51
4504036379004550.66
5256089611,2005400.82
6008681,1201,3726600.97
Ecosol Drop Trap 15003001302164002400.70
3752483926003450.86
4504036379004551.12
5256089611,2005401.38
6008681,1201,3726601.64
  1. Treatable Flow Rate (TFR) is the maximum flow the unit can treat without by-pass in a surcharged pit based on outlet pipe gradients up to 5%. It is important to note that the TFR will decline as the basket fills with pollutants.
  2. By-pass capacity is the maximum flow that can by-pass through a surcharged unit based on the nominated minimum drop of from inlet invert to outlet obvert.
  3. Headloss figures quoted refers to the head above the upstream pipe invert level in a surcharged environment with full impermeable basket and full pipe flow (worst case scenario).

The Ecosol Drop Trap has been subject to a range of field-based tests where it has demonstrated effective performance in retention of stormwater gross pollutants (>3mm), hydraulic capacity and durability for the environment in which it operates.    The below Particle Size Distribution graph confirms how efficient the product is at retaining coarse sedimentation conveyed in stormwater surface runoff.

In recent years modern Water Sensitive Urban Design (WSUD) objectives and principles now applied to most urban development’s require more onerous water quality objectives (WQOs) specifically targeting the removal of suspended solids, nitrogen, phosphorus and heavy metals.  The Ecosol Drop Trap is an integral part of the treatment train providing essential pre-screening of stormwater flows, and when used in conjunction with other treatment measures such as swales or sand filters will achieve target water quality objectives.

Ecosol recognises that modelling of stormwater treatment systems is an integral part of WSUD engineering procedures today.  To assist you with your next project we are pleased to provide you with some indicative capture efficiency values for the Ecosol Drop Trap.

Ecosol DROP TRAP CAPTURE EFFICIENCY PERFORMANCE SUMMARY
Ecosol Drop Trap Capture Efficiency Performance Summary - 2018
PollutantsPollutant Capture
Efficiency (%)
Description
Gross Litter98%Anthropogenic material such as cans, bottles, plastic bags and packing material (generally >3mm in diameter).
Vegetation 98%Organic matter such as leaves and grass clippings.
Coarse Sediment 98%Solid material varying in size (generally >3mm in diameter) both mineral and organic.

In recent years modern Water Sensitive Urban Design (WSUD) objectives and principles now applied to most urban development’s require more onerous water quality objectives (WQOs) specifically targeting the removal of suspended solids, nitrogen, phosphorus and heavy metals. The Ecosol Drop Trap is an integral part of the treatment train providing essential pre-screening of stormwater flows, and when used in conjunction with other treatment measures such as swales or sand filters will achieve target water quality objectives.

Ecosol recognises that modelling of stormwater treatment systems is an integral part of WSUD engineering procedures today. To assist you with your next project we are pleased to provide you with some indicative capture efficiency values for the Ecosol Drop Trap.

Ecosol DROP TRAP TYPICAL PRODUCT CAPTURE EFFICIENCY
Ecosol Drop Trap Typical Product Capture Efficiency - 2018
PollutantsPollutant Capture Efficiency (%)Description
Gross Litter98%Anthropogenic material such as cans, bottles, plastic bags and packing material (generally >3mm in diameter)
Vegetation98%Organic matter such as leaves and grass clippings
Coarse Sediment98%Solid material varying in size (generally >3mm in diameter) both mineral and organic

As with all filtration systems, the Ecosol Drop Trap should be cleaned regularly.  The cleaning frequency and the cost depend heavily on the surrounding environment, the unit’s proximity to a waste facility, the quantity and quality of stormwater, the catchment, and the type of pollution collected. The figures in the table below give a broad guideline about the optimal catchment size and the number of cleans required annually based on typical developed urban catchment.

One of the key advantages of the Ecosol Drop Trap is that a small crane truck can easily lift the filtration basket for cleaning or alternatively is can also be easily cleaned from the surface using an industrial vacuum truck.

A key benefit of this primary treatment device is its low capital cost along with its low ongoing cleaning and maintenance cost.

Ecosol DROP TRAP RECOMMENDED CLEANING FREQUENCIES
Ecosol Drop Trap Recommended Cleaning Frequencies - 2018
Ecosol Drop Trap Product CodeMaximum Pipe SizeGross Pollutants Holding CapacityOptimal Catchment Area (Ha)Recommended Cleaning Frequency
mmm3HaPer Annum
Ecosol Drop Trap 1200600 RCP0.973.401
Ecosol Drop Trap 1500600 RCP1.645.901
lvenessEcosol Drop Trap