Tech & Tools

Technical information

Filtration pond rehabilitation work (sand reverse system)

Filtration pond rehabilitation work at water purification plant

Filter media, which is the heart of producing safe tap water, gradually becomes contaminated with long-term use. In addition, the filtered gravel becomes a [non-land] state where the surface becomes uneven due to repeated cleaning. The work to prevent the deterioration of tap water quality due to the contamination of the filter material and the non-landing of the filtered gravel is called [filter pond rehabilitation work] and is carried out at many water purification plants. .. Filtration pond rehabilitation work includes [1] cleaning of filter media, particle size adjustment, re-laying, [2] cleaning of filtered gravel, re-laying, [3] repair of lower catchment part, [4] painting of filter pond side wall. ・ Repair will be carried out.

Cleaning and particle size adjustment of filter media

Pollutants related to filter media are roughly classified into [adherent substances] represented by SS and turbidity and [adherent substances] represented by manganese and aluminum. Of these, [adherent substances] can be removed by relatively light cleaning of the filter material, but it is difficult to remove [adhesive substances] that are coated on the filter material due to chemical action. Therefore, we have independently devised a filter media cleaning device [Sand Actor] that enables the [adhesives] to be satisfactorily peeled off from the filter media without reducing the effective diameter of the filter media. The total rehabilitation work system, which adjusts the particle size (adjustment of effective diameter and uniformity coefficient) along with the finish rinsing of the filter media, was named [Sand Reverse System], and it has become possible to carry out the work efficiently by continuous processing.

This method not only saves money compared to using a new filter medium, but also reduces the environmental load by effectively using natural resources, meeting the needs of customers who have acquired ISO14000 series certification.


We manufacture and sell not only filter media but also equipment such as chemical injection pumps and water quality measuring instruments. From that experience, we design and manufacture not only filtration equipment but also various water treatment unit equipment. We will propose the optimum process based on many years of experience in order to realize the water treatment desired by the customer.

1. Arbitrarily set the degree of cleaning according to the contamination status of the filter media currently in use.
2. Do not destroy the filtered sand itself
3. The cleaning turbidity after rehabilitation is 30 degrees or less, which is the standard for new sand.
4. Particle size adjustment according to your request
5. High-speed processing by continuous loading type
6. The filtration pond rises quickly after rehabilitation
7. Reduction of wash water by circulation in the system
8. Since the cleaning device is unitized, it is easy to install on site.

Basic principle of filter media cleaning device [Sand Actor (PAT.Pend)]

The specially shaped cleaning blades and transfer blades attached to the two shafts inside the sandactor rotate to rub the sand and transport it to the discharge side at the same time. Contamination Various types of dirt adhering to and adhering to the filter media are efficiently peeled off without crushing the filter sand itself by entwining the sand with each other like polishing rice in the sand actor. This action makes it possible to continuously remove stubborn deposits at high speed, which was not possible with conventional methods.

Flow of sand reverse system type filter material rehabilitation work

1.Pre-construction survey
■Filter material contamination survey
Investigate the contamination status of the filtered sand during use according to the JWWA water filter media sand test method “Appendix I, Test method for filtered sand and anthracite in use”.
This value will be the basic data for future filtration pond operation management. This number sets the cleaning strength of the sand reverse.
■Filter layer thickness survey
Investigate the current filter layer thickness and gravel layer non-landing conditions, and use it to determine the risk of deterioration of treated water quality and outflow of filter media. The non-landing of the gravel layer is a phenomenon that directly affects the filtered sand layer, which is the heart of filtration, and it is a content that should be grasped from the viewpoint of water quality management. Also prepares a report so that the current situation can be easily understood.
2.Rehabilitation work
■Carrying out filter media
The filter material is taken out from the filter pond. Depending on the site conditions and purpose, it will be carried out by a belt conveyor, a powerful suction vehicle, a jet ejector, etc. At our company, skilled workers perform the work carefully, which leads to the discovery of abnormal parts that cannot be grasped by the filter layer thickness inspection.
Carrying out filter media
■Filter media cleaning and sieving
Clean to the desired value with the sand reverse. If you wish, we will adjust the particle size. If there are restrictions on the acceptance of wastewater, use a combination of wastewater treatment plants.
Filter media cleaning and sieving
■Cleaning and repair of the inside of the filtration pond
We clean, repair and paint the walls, water collection parts, pressure chambers, etc. inside the filtration pond.
* It is recommended to repair the water collection part, etc., which can be seen only when the entire amount of filter media is carried out, at the same time as the rehabilitation work.
* At our company, skilled special workers will properly construct the parts that need repair.
Cleaning and repair of the inside of the filtration pond
■Filter material filling and leveling
Skilled workers carefully fill and level the filling with a crane, jet water jet, belt conveyor, etc. according to the design value.
* This work requires special expertise, and it is important to work carefully because each gravel layer is thin.
Filter material filling and leveling
3.Post-construction survey
In order to understand the condition of the filter material and the condition of the filter layer thickness after the construction, we will conduct the same survey as before the construction.
* This survey can be compared with the state before construction, which can be useful for future operation management.
Post-construction survey

Comparison test results for filtered sand in use

Cleaning turbidity Hydrochloric acid solubility Effective diameter Equal coefficient Remarks
Pre-rehabilitation filtered sand (dirty sand) 800 degrees 4.5% 0.62mm 1.33
Conventional cleaning sand 100 degrees 3.0% 0.62mm 1.38 Throughput 2.5m3/h
Sandactor® type cleaning sand 14 degrees 2.1% 0.62mm 1.32 Throughput 5m3/h
  • Before cleaning
  • After cleaning


Head Office

1-12-11 Tagawakita, Yodogawa-ku,Osaka

Overseas Business Department

TEL +81-6-6301-6460
FAX +81-6-6308-3022