The final nail in the coffin—RIP: SBR STP

July 1, 2018

For several years now, after our detailed investigation and study of various STP technologies in the year 2011, we have been strident opponents of the SBR (Sequencing Batch Reactor) and the MBBR (Moving Bed Biofilm Reactor) technologies for micro, mini, and small STPs. 

 

But let’s first define what we mean by micro, mini, and small STPs in terms of their capacities:

 

Micro     10 - 50 KLD

Mini        50 - 100 KLD

Small      100 - 5000 KLD  ( 5 MLD)

 

Now we are not against either SBR or MBBR—in fact as qualified, experienced, and actively practising Environmental and Chemical Engineers we understand benefits of these fine technologies, but only when applied under appropriate circumstances. In the case of STPs, it is simply a matter of scale.  We would vociferously plug for an SBR or MBBR for a Municipal STP of say 10 MLD and above.

 

With that introduction, let’s get down to brass tacks.

 

 

Let’s take a real-life example of an SBR STP we had the misfortune to audit a few days ago. The claimed capacity was 120 KLD. However, using universally accepted norms of design and engineering criteria for an SBR, this STP can theoretically handle only 90 KLD. In practice, it would be much less, in addition to the various other constraints and high risk potential of an SBR, including poor sludge handling, odour generation, choking of filters, lower life expectancy of membrane diffusers, etc.

 

The STP is located in a fancy villa development with a Gran-diose Address on Sarjapur Road in Bangalore. It boasts a Mumbai-based developer, a UK-based architect, and maybe even a UK-based plumbing consultant, and a pliable local vendor of STP who does not even understand the ABCs of an SBR STP.

 

As an aside, we have a healthy disrespect for these foreign architects. Just a couple of years ago, we had occasion to confront the local branch of a highly-acclaimed Singapore-based architect on three occasions in quick succession on their choice of STP technology. The first one was an EADOx (Electrocoagulation) STP, the next was an SBR and the third was an MBBR, all for STPs in the range of 300 KLD capacity.  Surely this architect is clueless, if he can offer three vastly different technologies for almost identical applications.

 

Check out our presentation here about the various STP technologies

 

We will now take you through the SBR STP in some detail, and follow it up with a proper, scientific design of a 120 KLD Extended Aeration Activated Sludge (EAAS) STP, meticulously following every design and engineering criterion laid down in the STP Guide published by the Karnataka State Pollution Control Board (KSPCB). This will highlight to you, with sharp contrast, why an EAAS STP is by far the superior technology for small-scale STPs.

 

Two main advantages touted for an SBR’s superiority (footprint and energy) over the EAAS system are blown to smithereens in this real-life comparison, which will show you that contrary to what the proponents of SBR for small STPs would have you believe:

  • SBR does not have a smaller footprint compared to EAAS

  • SBR does not consume less energy than the EAAS

Let us once again assure you that these are the correct numbers, figures, and equipment specifications from an actual SBR and not an imaginary theoretical exercise.

 

We urge young, budding, upcoming environmental engineers to spend some time studying the technical presentation in the next three pages in some detail.

 

A real-life SBR

 

Below is the drawing of an actual SBR STP – 120 KLD (per design) at GR- - C-R- -N A-D--SS, Bangalore. Note that this design can only handle 90 KLD per universally-accepted norms of SBR design and engineering.

 

The tank volume calculations are as follows:

 

The total footprint:

The total power consumption:

 Note: Sludge is dewatered by draimad bags in the STP

 

EAAS Alternative

 

Scientifically designed 120 KLD EAAS STP following all design criteria laid down by KSPCB in their STP Guide.

 

Total footprint Area Occupied = 4.4m X 14m = 62 sq. m.

Power Consumption:

 Note: Sludge is dewatered by draimad bags in the STP

Comparison of SBR and EAAS

 

SBR system : 3 batches/day : 30 KL/batch : 90 KLD ONLY

 

EAAS system with air-lift sludge recirculation : 120 KLD

 

Therefore this 90 KLD SBR consumes 44% more energy than a 120 KLD EAAS STP.

Summary and Conclusion

90 KLD SBR compared to 120 KLD EAAS

  1. 69% larger volume

  2. 48% larger footprint

  3. 44% higher energy consumption

Case Closed.  Lifetime ban to be imposed on such architects, their plumbing consultants and vendors who collude with them to pollute the environment (a criminal offense), hoodwink innocent citizens, and deplete our precious fresh water supply.

 

 

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