Cloth Disk Filter Sludge Blanket Filtration
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Solution Overview
Problem
Conventional cloth disk filters face issues with increased cake resistance and short filter run due to chemical floc accumulation, leading to high filtration headloss and frequent backwashing, which reduces the effective filtration area and affects effluent quality.
Innovation Solution
Implementing a sludge blanket filtration system in conjunction with cloth disk filters, where a suspended solids stream flows upward through a sludge blanket region, forming a solids-enriched sludge blanket that reduces the load on the cloth filter media, and using rotating or sliding backwash arms to clean substantially all filter surfaces efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If chemical treatment is used to remove solids from wastewater, then solids removal efficiency is improved, but cake resistance increases quickly leading to high filtration headloss
Solution Approach 1:
The filtration process is segmented into two distinct stages: a sludge blanket region for initial solids removal and a cloth filter media region for final polishing. This segmentation allows chemical floc to be partially removed in the sludge blanket before reaching the cloth filter, reducing cake resistance and filtration headloss while maintaining solids removal efficiency.
Solution Approach 2:
A sludge blanket acts as an intermediary layer between the influent wastewater and the cloth filter media. This sludge blanket pre-treats the water by removing a portion of solids and chemical floc, thereby protecting the cloth filter media from rapid cake buildup and reducing the frequency of backwashing required.
2Reliability
If backwashing is performed frequently to maintain filtration efficiency, then effluent quality is maintained, but the effective filtration area is reduced and productivity decreases
Solution Approach 1:
By segmenting the filtration system into a sludge blanket region and a cloth filter media region, the system reduces the frequency and intensity of backwashing required for the cloth filter. This allows a larger portion of the cloth filter surface to remain effectively available for filtration at any given time, increasing productivity while maintaining effluent quality.
Solution Approach 2:
The sludge blanket performs preliminary solids removal before water reaches the cloth filter media. This preliminary action reduces the solids load on the cloth filter, delaying the point at which backwashing becomes necessary and thereby increasing the effective filtration area available for productive filtration.
3Reliability
If a rotating backwash arm is used to clean the filter surface, then backwashing capability is provided, but mechanical complexity increases and reliability decreases
Solution Approach 1:
The backwash pump and its associated rotating arm mechanism are completely extracted from the system. Instead, a simple bottom-drawbackwash method is used where backwash water is drawn directly from the bottom of the vessel through a central conduit, eliminating complex rotating joints, seals, and drive mechanisms while maintaining effective backwash functionality.
Solution Approach 2:
The system uses the weight and flow of backwash water itself to achieve the cleaning function. Backwash water enters at the bottom and flows upward through the cloth filter media, automatically lifting and cleaning the filter surface without requiring any mechanical moving parts or external actuators.
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 approach reduces the load on the cloth filter media, increases the usable filtration area by up to 30%, decreases backwashing requirements, and maintains or improves effluent quality, while potentially eliminating the need for a backwash pump and reducing mechanical failures.
Implementation Method 1
a suspended solids stream flows upward through a sludge blanket region, thus forming a partially treated effluent composition and a solids-enriched sludge blanket
Implementation Method 2
flowing the partially treated effluent composition generally upward to a cloth filter zone in the vessel, the cloth filter zone comprising at least one cloth filter media cassette, producing a filter cake on external surfaces of the cloth filter media and a treated effluent stream
Data Source
AI summary
Methods and apparatus for treating water and wastewater include the step of flowing a suspended solids stream generally upward through a sludge blanket region of a cloth disk filter vessel, thus forming a partially treated effluent composition and a solids-enriched sludge blanket. The partially treated effluent composition is allowed to flow generally upward to a cloth filter zone in the vessel after contacting the sludge blanket. The methods include flowing the suspended solids stream through one or more distribution headers positioned in the sludge blanket. An option is to provide a sludge concentration zone in the sludge blanket region, allowing sludge to flow into the sludge concentration zone to form concentrated sludge. Other methods and apparatus include backwash assemblies that backwash substantially the entire filter cassette surfaces, with or without use of a sludge blanket zone. Either the backwash assemblies or filter cassettes move in the latter methods and apparatus.