CellCap®, cellulose recovery from airport water
Introduction situation
The WWTP of an airport receives the sewage from the airport (including the water flow from the vacuum toilets of the aircraft) and from the industry present there. The average daily flow rate of a specific WWTP is 4,000 m³/day. The flow rate can be divided into approximately 250 m³/h for 14 hours during the day and approximately 100-120 m³/h for 10 hours during the night.
In the current situation, the sewage enters through the rake grate. The toast is cut. The water is then pumped directly to the biological purification. The composition of the sewage varies during the day and contains a relatively large amount of cellulose, which comes from toilet paper.
Introduction of the technology:
The operation of the IntenSieve® fine screen is based on a rotating endless screen cloth. A schematic cross-section of the CirTec fine screen is shown below.
The water is fed into the receiving compartment of the machine. The flow is first filtered through the filter cloth with the filter layer built up on it. The filter layer, also called precoat, formed by the suspended matter present in the (waste) water, makes it possible to capture particles that are much smaller than the mesh size of the installed screen cloth. Below is the formed precoat as found in practice on the sieve.
surface of the cloth transports the separated residue to the dump, where low pressure air blows the screened material from the cloth into the compartment of the discharge screw. By checking the water level in front of the filter and adjusting the belt speed in function of this level, a maximum filter cake layer is created and an optimum efficiency is obtained.
Research conducted
In order to be able to expand the treatment, a number of options are being considered, including the use of a fine sieve to treat the influent. In February and March 2017, a pilot test with a small full-scale installation was carried out on the influent with different mesh sizes of screen cloth. The focus was on the achievable removal efficiencies of the fine sieve on the influent. The pilot was carried out on a partial flow, in which the supply pattern to the treatment plant was followed.
| Characteristic | Value |
| Brand fine sieve | CirTec, smallest type |
| Length skid | ca. 4m |
| Skid width | ca. 2,4 m |
| Effective sieve surface | 0,25 m2 |
| Mesh width screen cloth | 500 en 840 micron |
| Feed rate pilot during tests | 10 – 70 m3/u |
Conclusion
Fine sieve technology can be well applied to sewage from an airport. By using a fairly coarse cloth, a lot of cellulose-containing sieves can be captured by using cake filtration on a rotating belt sieve. This sieve material has potential for further processing to a pure quality cellulose.
CellCap®, the right quality cellulose capture in one step
It is also possible to filter good quality from the incoming water in one step using a CellCap®. CellCap® is a combination of the CellWash® and the IntenSieve®. The combination of these two machines ensures the desired good quality of cellulose for reuse.
The CellWash consists of a fine-mesh drum from which the cellulose fibers can escape via an inventive feed system, while hairs, leaves, seeds and other unwanted components are captured. The ‘clean’ cellulose is then captured in the second phase, the IntenSieve®, a rotating belt screen, in which two critical processes are also combined in one compact unit, namely cellulose separation and thickening.
Because both process components are fully coordinated with each other and all connections of the machines are aligned, the hydraulic profile hardly differs from the IntenSieve® alone.
