BAF BIOSTYR (R)

BIOSTYR (R) is an improved new generation of Upflow Biological Aerated Filter. It can not only be used for the secondary treatment of sewage, but also for the advanced treatment of sewage which needs to be reused and other requirements, and can reach a very high discharge water quality standard.

Basic structure

BIOSTYR (R) process is a submerged upward flow biofilter. Its filter material is spherical particles with a small proportion and floating in the water. We call it biostyrenetm.

Each biofilter unit includes:

*The water inlet pipe and the water distribution channel at the bottom of the filter (which can also be used for the discharge of backwash water);

*Two air pipes, one for process aeration and one for air backwash; two pipes are used for nitrification / denitrification reaction, and the same pipe is used for aeration and backwash in single nitrification reaction;

*3-3.5m filter material layer, with a large number of microorganisms attached to the surface of the filter material;

*A concrete filter plate is arranged on the top of the filter tank to prevent the loss of filter materials;

*A filter head is installed on the filter plate to discharge water from the filter.

Technological principle

The degree of nitrification and denitrification can be controlled according to the different positions of aeration pipes, and nitrification or denitrification can be carried out separately.

BIOSTYR biofilter with nitrification and denitrification functions, whose aeration pipe is located in the calculated position of the filter bed, divides the filter bed into the lower anaerobic area and the upper aerobic area, which can remove all degradable pollutants, including carbon pollutants (COD and BOD), suspended solids (SS), ammonia nitrogen and nitrate (i.e. total nitrogen), and the backwash gas pipe is located at the bottom of the filter.

Generally, only nitrification is needed (ammonia nitrogen is required), and a perforated pipe at the bottom of the filter is shared during aeration and air backwashing, so that the whole filter bed is in aerobic state, which can remove most of the degradable pollutants, including carbon pollutants (COD and BOD), suspended solids (SS) and ammonia nitrogen.

Water distribution and inflow: the water from the primary treatment or secondary treatment is evenly distributed to the inflow channel of each filter tank through the water distribution weir, and then flows into the distribution channel at the bottom of the filter tank by gravity through the inlet pipe. An automatic valve is installed on the inlet pipe or channel for stopping the inflow in some cases (such as in the process of backwashing), and the sewage enters into the whole through the distribution channel at the bottom of the filter tank Filter, these designs ensure that the filter in the entire section of the uniform distribution of water. Different from downflow filter (for example, the proportion of filter material is greater than 1), the head of the filter ensures the uniformity of water inlet and distribution, so the filter head (which is easy to block) or distribution network is no longer required at the bottom of the filter, and the screen is not required before treatment.

Filter material: biostyrenetm filter material is a kind of spherical filter material with small particle size and uniform shape. Its specific gravity is less than 1, and it has a large specific surface area, which makes it have the following characteristics:

*The filter material has large specific surface area, high purification capacity and high treatment load;

*Good mechanical and physicochemical properties, not easy to wear;

*The raw material of filter material comes from domestic industrial raw material, which can be produced and processed on the spot with low cost;

*The loss of filter material is very small, so it hardly needs to be replaced.

A large number of microorganisms are attached to the huge surface area of the filter material as the carrier of microorganisms. Under the effect of oxygen provided by the bottom aeration pipe, the carbon pollutants (COD and BOD) in the sewage are degraded, and the ammonia nitrogen is oxidized to nitronitrogen.

In the case of nitrification / denitrification, the treated effluent needs to be refluxed. The return water and raw water are mixed in the inlet channel and then enter the filter. The sewage first enters the anaerobic area at the bottom of the filter bed, where denitrification is carried out to remove the nitro nitrogen in the return water; then it enters the aerobic area at the top, where the carbon pollutant is decomposed and the ammonia nitrogen is converted into nitro nitrogen.

Because the mechanism of nitrification and denitrification is greatly affected by the influent water temperature, the low influent water temperature will obviously affect the tank capacity of biochemical reaction. However, BIOSTYR (R) filter has enough residence time (1-2 hours) and process air continuously bubbling in at 80-100 ° C, so the biochemical reaction is very little affected by the external climate conditions. At the same time, because the microorganism in the filter is fixed on the carrier, rather than suspended in the water like the activated sludge method, the biomass per unit volume is very large, which improves the treatment efficiency 。 Because of the above two reasons, the lower inlet water temperature has little effect on its biochemical reaction, and BIOSTYR (R) filter can operate normally in the range of 8-30 ° C.

Finally, the direction of sewage flowing through the filter bed is the direction of compressing the filter material, rather than expanding the filter material, which also strengthens the retention of suspended substances, so that no sedimentation tank is needed.

Treated water of filter tank: the floating filter material is blocked in the filter tank through the concrete cover plate, and there are many filter heads installed on the cover plate, which can make the treated water flow out. Because these filter heads only contact with the treated water, the blockage is avoided; at the same time, because there is no filter material on these filter heads, it is easy to maintain.

Filter backwash: with the interception of suspended substances and the continuous growth of biofilm, the filter bed needs to be backwashed regularly, i.e. gravity backwash and air backwash. The water after backwash is collected and discharged into a sump by the sump at the bottom of the filter (i.e. the underground intake channel). Backwashing water is the clear water layer with a certain height stored on the filter plate at the top of the filter tank. The clear water layer is connected in a group of filter tanks. The height of the clear water layer is calculated to make the water stored enough for backwashing of the filter tank. Since backwashing is carried out by gravity and in the opposite direction of normal filtration, backwashing water pump is no longer required.

Regular reverse flow backwashing can remove the excess biofilm and suspended solids without passing through the whole filter bed. The downward water flushing can flush the intercepted material out of the filter bed in the shortest route, and it is the direction of gravity falling of the intercepted material, saving energy consumption and high efficiency.

The backwashing process is as follows:

*Close the water inlet valve of the filter and open the backwash drainage valve at the bottom of the filter;

*The clear water at the top of the filter flows down by gravity for pre washing;

*Then air water combined recoil is carried out with air recoil;

*Wash with air only and water only alternately;

*Finally, rinse with water only.

There are two control procedures for backwashing: time control (normally 24-hour backwashing once) and pressure difference control (automatic start-up and operation through the pressure difference between the upper and lower filter layers).

Aeration of filter: the process air and backwash air of each filter are supplied by the same blower bank, and the blower does not stop working. However, in the nitrification / denitrification filter, their gas distribution network is separated and switched by valves; in the single nitrification filter, the process air and backwash air are the same gas distribution network, and the gas supply of the two modes is regulated by the regulating valve at the filter inlet.

Process performance of filter: BIOSTYR (R) filter can be divided into carbon removal type, nitrification type, nitrification / denitrification type and post denitrification type according to different pollutants removal.

Due to the huge and abundant biofilm attached to the filter material, the treatment capacity of BIOSTYR (R) filter is much higher than that of activated sludge process.

Main advantages

*Because BIOSTYR (R) process combines filter and biochemical reactor, no sedimentation tank is needed;

*It covers a small area, which is 1 / 4 ~ 1 / 5 of the conventional technology, saving a lot of land acquisition and foundation treatment costs;

*The pool capacity is small, and the civil engineering quantity is 20% - 40% less than other processes;

*All modular structure, easy reconstruction and extension, short construction period;

*The upper outlet water is clear water, the filter head is not easy to block, and maintenance and replacement are easy. No need to empty the filter material in the filter;

*It can completely close the plant area without odor pollution and has good visual and landscape effects;

*There is no need for separate backwash water and backwash water pump, which reduces equipment investment and operation cost;

*Perforated pipe aeration, saving equipment investment and maintenance costs, high efficiency. However, the membrane aerator usually loses its efficiency after two years of operation;

*High degree of automation, few operators; * stable operation at low temperature, little affected by temperature;

*Because of its continuous physical filtration ability, once the biological reaction occurs problems, the filter still can remove most of the suspended solids, and it only takes a few days to restore the biological treatment capacity, while the activated sludge method takes a few weeks to restore;

*The process operation is flexible, and the denitrification function of nitrification can be completed in the same filter tank at the same time.