What factors affect the treatment effect of MBBR process?

1. Filler characteristics
Filler type:
Fillers of different materials have an impact on the treatment effect. For example, polyethylene and polypropylene fillers have good chemical stability and wear resistance, and are suitable for long-term use; while fillers of materials such as polyurethane may have a higher specific surface area, which is conducive to the attachment and growth of microorganisms, but the cost may be relatively high.
The shape of the filler is also very important. For example, the movement state and microbial attachment of fillers of different shapes such as cylindrical and spherical shapes in the water flow may be different.
Specific surface area:
The larger the specific surface area of ​​the filler, the larger the space available for microorganisms to attach and grow, so that more biomass can be accommodated and the treatment effect can be improved. Generally, fillers with a specific surface area of ​​more than 300 square meters/cubic meters can provide better treatment effects.
However, too large a specific surface area may also increase the water flow resistance between fillers, affecting the operating stability of the system.
Porosity:
Fillers with high porosity are conducive to the passage of water flow and the transfer of oxygen, providing a good growth environment for microorganisms. The porosity is generally more than 90%.
At the same time, porosity will also affect the biofilm growth rate of the filler and the renewal rate of the biofilm.

2. Hydraulic conditions
Water flow rate:
The appropriate water flow rate can ensure that the filler is fully suspended and mixed in the reaction tank, promoting the contact between microorganisms and sewage. If the water flow rate is too low, the filler may settle, resulting in a reduction in local biomass; if the water flow rate is too high, it may cause scouring of the biofilm and cause the biofilm to fall off too quickly.
Generally speaking, the water flow rate is more suitable between 0.2 and 0.5 m/s.
Hydraulic retention time:
Hydraulic retention time (HRT) directly affects the treatment time of sewage in the reaction tank. A longer HRT can give microorganisms enough time to degrade pollutants, but it will reduce the treatment capacity; a shorter HRT may lead to inadequate treatment.
According to different water quality and treatment requirements, HRT is usually adjusted between 4 and 12 hours.
Mixing degree:
Good mixing can ensure that pollutants in sewage are evenly distributed and increase the contact opportunities between microorganisms and pollutants. The mixing effect can be enhanced by agitators, aeration, etc.
However, excessive mixing may destroy the structure of the biofilm and affect the treatment effect.

3. Biological factors
Microbial species and activity:
Different types of microorganisms have different degradation abilities for different pollutants. For example, nitrifying bacteria and denitrifying bacteria play a key role in removing nitrogen pollutants, while polyphosphate bacteria help remove phosphorus.
Maintaining high activity of microorganisms is the key to improving treatment effects. Microbial growth and metabolism can be promoted by controlling environmental conditions such as temperature, pH value, and dissolved oxygen.
Biofilm thickness:
When the biofilm thickness is moderate, it can ensure sufficient biomass for pollutant degradation and the transfer of oxygen and nutrients. If the biofilm is too thick, it may cause internal hypoxia and affect microbial activity; if the biofilm is too thin, the biomass is insufficient and the treatment effect is reduced.
Generally speaking, the biofilm thickness is more appropriate between 0.2 and 0.5 mm.
Biofilm renewal rate:
An appropriate biofilm renewal rate can remove aging biofilms and maintain the activity of biofilms. The renewal of biofilms can be promoted by water flushing, aeration, etc.
However, too fast a renewal rate may cause excessive biomass loss, affecting the treatment effect.

4. Operating conditions
Temperature:
Temperature has an important influence on the growth and metabolism of microorganisms. Most microorganisms have high activity between 20-35℃. Under low temperature conditions, the activity of microorganisms will decrease and the treatment effect will decrease; under high temperature conditions, microorganisms may be inhibited or even die.
For areas with low temperatures in winter, insulation measures can be taken or microbial strains that adapt to low temperature environments can be selected.
pH value:
The suitable pH value range is generally 6.5-8.5. Deviating from this range, the activity of microorganisms will be affected, thereby reducing the treatment effect.
The pH value of sewage can be adjusted by adding acid-base regulators.
Dissolved oxygen:
Dissolved oxygen is a key factor for aerobic metabolism of microorganisms. For aerobic treatment processes, the dissolved oxygen concentration should generally be maintained at 2-4 mg/L.
Sufficient dissolved oxygen can be provided by aeration equipment. At the same time, care should be taken to avoid excessive aeration to avoid damage to the biofilm.

If you want to know the factors that affect the treatment effect of MBBR process, you can contact BioCell Environmental Technology, we will do our best to help you!

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