MBR process for sewage treatment

The SBR process also has unique features. The overall advantages and disadvantages are as follows:

advantage

The processing process is simple:

There are five stages in the process: water intake, aeration, precipitation, drainage and standby.

Intermittent aeration, unstable biochemical reaction instead of steady biochemical reaction,

Static ideal precipitation replaces traditional dynamic precipitation.

Small number of structures, low cost:

There is no need to set up a primary settling site, and there is no need to set up a secondary settling site, and the sludge return facility, regulation tank and primary settling tank can also be omitted.

Easy operation and maintenance management. The disadvantages of low efficiency and large footprint of traditional anaerobic reactor are avoided.

Simple structure

The combined construction method is beneficial to the expansion and renovation of the wastewater treatment plant.

The effluent water quality after treatment is good.

Good automatic control system, good nitrogen and phosphorus removal effect, wastewater discharge standards, several said that the average removal rate of CODCr can reach more than 94%, stronger than single-stage aerobic treatment process.

Orderly and intermittent operation on the run.

It is especially suitable for the treatment of wastewater which is difficult to biodegrade.

The problem that the acid accumulation in the hydrolysis and acidification stage of UASB and other high-efficiency anaerobic reactors is easy to inhibit the treatment efficiency of methanogenic stage is solved.

Small footprint, low energy consumption, investment, convenient operation and management

shortcoming

It relies heavily on modern automation control technology.

The degree of automation requires higher operation, management and maintenance, and the quality of operation and management personnel is required to be higher.

If manual operation is used, the aeration plate will be easily blocked due to the complicated operation of the water inlet and outlet process.

Scope of application

Small and medium-sized urban domestic sewage and industrial sewage of factories and mining enterprises, especially in places where intermittent discharge and flow change greatly.

Places that require higher water quality, such as scenic areas, lakes and harbors, not only need to remove organic matter, but also require the removal of phosphorus and nitrogen from the water to prevent eutrophication of rivers and lakes.

Where water is scarce. The SBR system can be used for physical and chemical treatment after biological treatment, and does not require additional facilities to facilitate water recycling.

Where land is tight.

The renovation of the existing continuous flow sewage treatment plant.

It is very suitable for the treatment of small water volume, intermittent discharge of industrial sewage and the treatment of dispersed point source pollution.

SBR design essentials

1. Determination of the operating cycle (T)

The operation cycle of SBR is determined by water filling time, reaction time, precipitation time, drainage time and idle time. Water filling time (tv) should have an optimal value. As mentioned above, the filling time should be determined according to the specific water quality and the aeration method used during operation. When the limited aeration method is used and the concentration of pollutants in the water is high, the water filling time should be appropriately longer. When the non-limited aeration method is used and the concentration of pollutants in the water is low, the water filling time can be appropriately shortened. The water filling time is generally 1 to 4 hours. Reaction time (tR) is a very important process design parameter to determine the volume of SBR reactor, and its value also depends on the nature of sewage during operation, the concentration of sludge in the reactor and the aeration method. For domestic sewage easily treated sewage, the reaction time can be shorter, and on the contrary, for sewage containing difficult to degrade substances or toxic substances, the reaction time can be appropriately taken longer. Generally in 2 ~ 8h. Precipitation drainage time (tS+D) is generally designed according to 2 ~ 4h. Idle time (tE) is generally designed in 2h.

One cycle takes time tC≥tR+tS+tD

Number of cycles n=24/tC

2. Calculation of reactor volume

Assuming that the amount of sewage in each series is q, the amount of sewage entering each reaction tank in each cycle is q/n·N. The volume of each reaction tank is:

V: Capacity of each reaction tank

1/m: discharge ratio

n: Number of cycles (cycles /d)

N: Number of reaction pools per series

q: Water intake per series (designed maximum daily sewage volume) (m3/d)

3. Aeration system

In the sequential batch activated sludge method, the capacity of the aeration unit should be the oxygen demand that can be supplied within the specified aeration time. In the design, the BOD per unit of inlet water is 0.5 ~ 1.5kgO2/kgBOD during high load operation and 1.5 ~ 2.5kgO2/kgBOD during low load operation.

In the sequencing batch activated sludge process, because the activated sludge is aerated and precipitated in the same reaction tank, the aeration unit must be not easily blocked, and the stirring performance of the reaction tank should be considered. Commonly used aeration systems include gas-liquid mixed injection, mechanical mixing, perforated aerator, microporous aerator, generally choose jet aeration, because it has a mixing effect in the non-aeration style, while avoiding blockage.