Gravity Sand Filter Backwashing with Disposable Media
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Solution Overview
Problem
Current filtration systems for tertiary cleaning in domestic wastewater treatment plants, such as membrane and gravity sand filters, are either operation-intensive and costly or require significant space and maintenance, making them unsuitable for small treatment plants.
Innovation Solution
A simplified filtration system using a gravity sand filter with a permeable divider and air-lift pumping for backwashing, eliminating the need for electric valves and manual operation, and utilizing hydrostatic pressure to manage sludge accumulation and filtration efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If membrane filtration is used for tertiary cleaning, then filtration quality is improved and all undissolved substances including bacteria are collected, but operational complexity and investment cost increase significantly
Solution Approach 1:
The patent employs a disposable filter medium (filter paper or non-woven fabric) that is replaced rather than cleaned, eliminating complex backwashing systems. This disposable approach maintains high filtration quality while significantly reducing operational complexity and investment costs compared to reusable membrane systems.
Solution Approach 2:
The invention extracts the filtration function from complex membrane systems and implements it through a simple gravity-based sand filter with a disposable filter medium layer. This extraction isolates the essential filtration capability while removing unnecessary operational complexity.
2Manufacturing precision
If membrane filtration is used, then filtration quality is improved, but investment cost increases
Solution Approach 1:
The patent replaces expensive reusable membranes with inexpensive disposable filter media (filter paper or non-woven fabric). This substitution dramatically reduces investment costs while maintaining adequate filtration quality for tertiary cleaning applications.
Solution Approach 2:
The invention creates a simplified copy of the membrane filtration function using common, inexpensive materials like filter paper and non-woven fabric, achieving sufficient filtration performance without the high cost of actual membrane systems.
3Volume of stationary object
If textile filtration is used, then space requirements are reduced, but it is only suitable for treatment plants with capacity over 100 m³
Solution Approach 1:
The patent changes the operating parameters by using gravity-driven flow instead of pressure-driven flow, and employs a disposable filter medium instead of textile media. This allows the system to achieve effective filtration in a compact design suitable for small treatment plants with capacities below 100 m³.
Solution Approach 2:
By using disposable filter media, the system becomes adaptable to various plant sizes including small installations, as the simple design requires minimal space and can be easily configured for different capacity requirements.
4Ease of manufacture
If gravity sand filter is used, then investment cost is reduced, but sludge accumulation reduces filtration efficiency over time
Solution Approach 1:
The patent employs a disposable filter medium that is replaced rather than cleaned. This eliminates the productivity decline caused by sludge accumulation, as each new filter medium starts with full filtration efficiency. The low cost of the disposable medium compensates for the replacement frequency.
Solution Approach 2:
The filter medium is pre-prepared and positioned before operation begins. This preliminary setup ensures optimal filtration efficiency from the start, and when efficiency declines due to sludge accumulation, the entire medium is replaced rather than attempting complex cleaning procedures.
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
This solution provides reliable and cost-effective tertiary treatment capable of producing high-quality purified water, suitable for small domestic wastewater treatment plants, with reduced operational complexity and space requirements.
Implementation Method 1
air-lift pumping for backwashing
Implementation Method 2
utilizing hydrostatic pressure to manage sludge accumulation
Implementation Method 3
permeable divider
Implementation Method 4
gravity sand filter with a permeable divider
Data Source
Figure 1
Figure 2
AI summary
The invention deals with a method of cleaning the filter medium of a gravity sand filter and a filter system. Therein the filter medium is placed on the divider, under which compressed air is brought, permeating through openings in the divider to the filter medium and on the way to its surface releasing turbidity to the water layer above the filter medium, when subsequently turbidity and water are drawn off. Compressed air brought under the divider pushes filtered water out of the space under the divider to the filtered water tank, while the volume of incoming compressed air per unit of time is larger than the volume of outflowing water pushed to the filtered water tank.