Three-Stage Surface Water Filtration Device
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Solution Overview
Problem
Traditional surface water filtration systems, such as grated catch basins, are ineffective in removing small particles, oils, and chemical contaminants, leading to system clogging and non-compliance with regulations, and are difficult to maintain, resulting in increased costs and environmental pollution.
Innovation Solution
A three-stage filtration apparatus comprising a primary grate filter, a secondary cylindrical perforate screen filter, and a tertiary non-woven sediment filter with media specific to the contaminants present, allowing for efficient removal of solids, oils, and chemicals, and easy maintenance by replacing components as needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional grated catch basin system is used for surface water filtration, then large debris can be caught and the system is relatively inexpensive, but small particles, oils, and chemical contaminants are not removed, leading to system clogging and regulatory non-compliance
Solution Approach 1:
The filtration system is divided into three distinct stages: primary filtration (grate) for large debris, secondary filtration (perforate screen) for small particles, and tertiary filtration (non-woven fabric with media) for oils and chemicals. Each stage handles specific contaminant sizes and types, improving overall reliability without requiring a single complex filter system.
Solution Approach 2:
The filters are arranged in a nested configuration where the secondary perforate screen is positioned inside the catch basin, and the tertiary non-woven fabric filter with specialized media is nested within or alongside the secondary filter. This nested arrangement maximizes filtration effectiveness while minimizing the overall footprint and structural complexity.
2Productivity
If a catch basin is used to collect sediment, then primary filtration is achieved, but the basin quickly fills with sediment causing overflow and clogging, and cleaning is difficult when the basin is underwater
Solution Approach 1:
By segmenting the filtration into three stages, each filter captures specific contaminant types and sizes. This prevents all contaminants from reaching the catch basin, significantly reducing sediment accumulation and maintaining filtration capacity without requiring frequent emptying or complex maintenance operations.
Solution Approach 2:
The primary and secondary filters perform preliminary filtration of solids and particles before water enters the catch basin. This preliminary action prevents sediment from accumulating in the basin, eliminating the need for difficult underwater cleaning operations and maintaining system productivity.
3Speed
If water flow through the basin is turbulent during storms, then water can flow through the system quickly, but very little sediment settles out and is instead washed through into the sewer system
Solution Approach 1:
The three-stage filtration system ensures that sediment removal does not depend on turbulent flow conditions. The primary grate catches large debris, the secondary screen captures small particles, and the tertiary fabric filter with specialized media removes oils and chemicals. This segmented approach maintains reliable sediment removal efficiency regardless of water flow rate or turbulence during storms.
Solution Approach 2:
The tertiary filter uses non-woven fabric with specific media (such as hydrophobic materials for oil separation or adsorbent materials for chemical contaminants) that changes the filtration parameters based on contaminant type. This allows effective removal of various contaminants across different flow rates without relying on sedimentation that requires low flow conditions.
4Ease of manufacture
If a grated catch basin system is used, then large objects are caught, but oils and chemical contaminants flow through the system and clog dry wells quickly
Solution Approach 1:
The system adds secondary and tertiary filtration stages that specifically target oils and chemical contaminants. The tertiary filter uses specialized media (such as hydrophobic materials, activated carbon, or other adsorbents) selected based on the specific contaminants present, providing reliable removal effectiveness while maintaining relative system simplicity through modular addition of filter stages.
Solution Approach 2:
The tertiary filter employs locally optimized media properties tailored to specific contaminant types. For example, hydrophobic media for oil separation, adsorbent materials for chemical contaminants, or biodegradable media for organic pollutants. This local quality approach ensures reliable contaminant removal effectiveness while keeping the overall system design simple and adaptable.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The apparatus effectively filters out a wide range of contaminants, reducing the risk of system clogging and regulatory non-compliance, while being easy to maintain and adapt to different environmental conditions, thereby improving water quality and reducing operational costs.
Implementation Method 1
Surface water flows through the grate, which catches large objects such as branches, rocks and the like
Implementation Method 2
The water that flows through the grate enters the catch basin, which is a collection box or vault that functions essentially as a settling basin. Some sediment that flows through the grate settles to the bottom of the basin
Implementation Method 3
A three-stage filtration apparatus comprising a primary grate filter, a secondary cylindrical perforate screen filter, and a tertiary non-woven sediment filter with media specific to the contaminants present
Implementation Method 4
The apparatus effectively filters out a wide range of contaminants, reducing the risk of system clogging and regulatory non-compliance
Data Source
AI summary
A plate is positioned across an inlet to a catch basin and a filter strainer is inserted through an opening through the plate and into the basin. A tertiary filter completely surrounds the strainer and is suspended below the plate. Surface water flows through a primary grate that covers the catch basin, through the strainer and through the tertiary filter. The tertiary filter comprising fibrous filter media retained in a non-woven mesh fabric enclosure and the filter media is selected according to the type of contaminants that are to be removed.