The applicable conditions, advantages and disadvantages of several commonly used filter tanks are as follows:

(1Ordinary rapid filter and double-layer filter

It is suitable for influent turbidity less than20NTUIn the short term, it can be less than50NTU. It is used in large, medium and small water treatment plants, and the area of a single pool is generally no more than100m2.

The operation and management of the common rapid filter tank is convenient, but it has many valve components and is prone to leakage, so a dedicated flushing device is required. The double-layer filter has a high filtration rate and a long working cycle, and can be transformed from a common rapid filter. However, the selection of filter materials is strict, the flushing operation is rather strict, and it is prone to sludge sedimentation.

(2Contact the double-layer filter

That is, direct filtering, applicable to5000m3/dFor the following small-scale water treatment plants, the influent turbidity requirement is less than150NTU.

Its advantages are that it can purify raw water at one time, requires fewer treatment structures, occupies less land, and has low infrastructure investment. However, the working cycle is short, the dosing management is complex, and the flushing operation is relatively strict.

(3Siphonic filter

It is applicable to large and medium-sized water treatment plants. The area of each pool is less than25m2The turbidity of the influent should be less than20NTU.

Its advantages are that the valve components are simple, no dedicated flushing equipment is required, and it can be automatically controlled. However, it needs to be equipped with vacuum pumping equipment. The pool is deep and the structure is complex.

(4Valveless filter

Valveless filters are divided into gravity type and pressure type. The area of a single gravity-type valveless pool is less than25m2It is suitable for small and medium-sized treatment plants, and the turbidity of the influent should be less than20NTU; The area of a single pressure valveless filter tank is less than5m2It is used in small-scale water treatment plants, with the influent turbidity requirement being less than150NTU.

Gravity valveless filter is very convenient to operate and manage. It can automatically backwash, but it is not convenient to clean the sand during maintenance. The use of pressure valveless filter tanks can eliminate the need for secondary pumping stations, but it is not convenient for sand cleaning, has a short working cycle, and the flushing operation control is relatively strict.

(5Pressure filter

It is suitable for small water plants, and the turbidity of the influent is less than20NTU. Its advantages are that the filter tank can be made of steel, which is highly flexible. It can be used in series with demineralized water treatment or softening treatment, and can also be used as a primary purification treatment without the need for a secondary pumping station. The disadvantages are that it is not convenient to clean the sand, the working cycle is relatively short, and it consumes a lot of steel when made with steel.