IS SLUDGE TREATED PROPERLY?
                                                               NO! SAYS Dr. Peter Maier

Dr. Peter Maier is a professional engineer who has been involved in design and R&D of municipal and
industrial wastewater treatment plants in Europe, Brazil, Mexico and the United States. For more
information visit Dr. Maier's website
http://www.petermaier.net/

Dr. Maier says:
I really appreciate what everybody is doing with research related to sewage treatment, but it is sad that there is so much time spent
on issues , while assuming that sewage is properly treated. There is no such thing as conventional activated sludge sewage
treatment. Statements like primary, secondary and tertiary treatment have no meaning and everybody can give them their own
definition.. All treatment plants that use bacteria to remove the otherwise  non-settling organic matter, are activated sludge systems,
but their efficiency depend on how much and what type of biomass is selected to be maintained in the system.  The same basically
as what the BOD test shows: the longer you keep the bacteria and waste in the test bottle the more waste is broken down and after a
30 day period at 20 degrees Celsius, you hardly have any biodegradable waste left.  Dr. Pasveer developed the oxidation ditch in the
forties and basically designed an activated sludge retaining system that kept the bugs and waste in it for 30 days or what is called a
SRT (Solid Retention Time) of 30 days. Since the waste is first adsorbed by the biomass, this adsorption time is important, but
much shorter as what is called the hydraulic retention time. In oxidation ditches this is about 24 hours, often confused with
treatment facilities (package plants) based on 24 hours of extended aeration. The result was that not only all the carbonaceous
waste, but also all the nitrogenous waste was utilized. Excess sludge (yes you will have non-biodegradable matter and you will grow
new bugs) could be disposed of on land and since the demand for oxygen was minimal and supplied by the air, this sludge would
not rot, thus stink.  The original ditch was operated in sequence, but engineers wanting to use the process, made it continuous by
adding clarifiers. This in turn limited the solid loading of the MLSS (Mixed Liquor Suspended Solids or amount of biomass) in the
activated sludge holding tank to 3 to 4 mg/l, while the  American design of final clarifiers only allows solid loadings of about 2 mg/l.
What this means is that these biological retention basins (aeration basins) have to be large and since engineers still prefer to use the
same equipment for aeration and mixing (a left-over from the days when factories had only one drive shaft for the whole factory) it
created a problem with aeration (only when necessary) and mixing (always necessary), limiting operation flexibility and wasting a lot
of energy.  Also completely ignored is the fact that raw sewage not only hourly fluctuates in flow, but also in concentration and
composition (carbonaceous and nitrogenous).  Based on the existing alleged proper theories, one can already prove that, due to these
fluctuations, sewage treatment plants, with a less than 25 day SRT (Solid Retention Tem) are impossible to operate, hence the many
problems experienced in the field.  Now the membrane people are claiming something new, while basically they do the same Pasveer
did in 1948, by maintaining a biomass with 30 day SRT and as they do not depend on the solid load limitations of final clarifiers,
they can indeed increase the MLSS to 20 mg/l and thus built much smaller activated sludge retention basins, without final clarifiers.  
What they do not tell you is since you deal with a filter, they get clogged and the question is how often do they have to be replaced
and at what cost.  A much simpler solution would be to go back to the original Pasveer oxidation ditches and make sure that short
circuiting does not occur during the settling sequence, one of the reasons engineers disliked the discontinuous operation without
stopping the inflow and came up with adding final clarifiers.  The fact is that you can achieve primary, secondary, tertiary treatment
results (whatever they are) in one single basin, provided the holding tank will retain the bacteria and food for 30 days and that they
all get food,  mixed well and provided with the necessary oxygen when they need it.  When you also get rid of the final clarifiers and
their solid load limitations, you saved yourself a lot of money and headaches.  Ultimate biological treatment at a fraction of the cost
now paid for 'conventional' systems, which basically are still designed as odor control facilities. Which sadly only can be proven by
testing correctly. This is clearly one major reason why the environmental industrial complex resist doing the proper testing.  My son
gave me a website
www.petermaier.net for Christmas and although not 100% complete it contains a lot of information, especially a
description of the BOD test and what the consequences are if you test as still is common in the whole world. Without correct
testing, I am afraid that this misunderstanding, that sewage is properly treated will go on and also opens the doors for many
black-box solutions for better treatment, that can not be evaluated.

Before we waste more time, let's insist that the correct testing is done, so we can evaluate how sewage treatment plants perform
and determine the pollution loading on receiving water bodies. By assuming that all activated sludge plants are equal, we really
compare apples with oranges. Living in the 21st Century, that should not be too much too ask!  

Regards,
Peter