An introduction to the SBR Process
Process Description
The common Enviros Sequencing Batch Reactor design SBR is an activated sludge, biological nutrient removal (nitrification) process, based on a cycle of operation. Denitrification, or the removal of total Nitrogen can also be provided as a refinement of this SBR process.
The duration of each cycle is typically twenty four hours.
Important features of the SBR technology include:-
- Optimisation of energy through control of aeration rate and duration;
- Elimination of the need for secondary clarifiers in most cases, and therefore a compact footprint;
- Removal of contaminants with minimum chemical addition through proper pH control and oxygen demand/supply management;
- Highly robust due to the large water volume provided which resides throughout at, or close to final effluent quality, absorbing shock loadings;
- Operation under continuous normal low loading conditions through simple cycle adjustment plus the ability to automatically convert operation to a high flow cycle of operation for extended wet weather periods;
- Operates with minimal sludge generation.
Principles of Operation
A basic Sequencing Batch Reactor (SBR) cycle comprises automatically set periods for:-
- Leachate Filling (Feed) during Aeration
- Settlement
- Decanting the treated Effluent.
During the aeration phase, the liquid volume inside the vessel increases from a set minimum operating (low) water level in response to a varying influent flow rate. After a settling period the treated (effluent) supernatant is removed (decanted), via a simple bellmouth or a moving/floating weir decanting system, after which the cycle is repeated.
AERATION: is to the airflow-on time during which time influent is received into the tank or lagoon. Multiple tank or lagoon facilities can be operated with different (staggered) start times for sequences of aeration (air-on) during the nominal aeration phase at each vessel. Operation at less than design load is typically achieved with a shortened aeration sequence, or fewer than the total number of aerators operating at any time.
SETTLEMENT: refers to the period after aeration during which time settling conditions are created in the previously aerated tank or lagoon, to allow the biomass (floc) to settle and therefore provide solids-liquid separation.
DECANTING: occurs once the settling phase is completed. Inflow to the process is suspended whilst decanting. The decanter is set to draw-off the treated effluent from its end-of-aeration-period rest position to a designated bottom water level position to decant the volume of overlying supernatant water (the treated effluent). Decanting may be direct to a sewer, consented watercourse discharge, or to a tertiary treatment system for further treatment.
Click here to see more about the SBR sequence.
Although the majority of our plants treat landfill leachate, we have also successfully designed and commissioned SBRs for a wide variety of industrial effluents, including paper mill effluent, and composting plant (windrow) storm water run-off. Contact us if you have a water treatment problem which you would like us to advise you upon.
Denitrification
Denitrification to reduce the total nitrogen in the effluent is readily added to SBR processes. The image on this page shows a denitrification trial in progress. The drum on the top of the wooden frame is the anoxic reactor this instance.
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