The Moos KSA-system and the polymers used for ... - Simon Moos A/S

This report is made by:
The Moos KSA-system
and
the polymers used for dewatering
Simon Moos Maskinfabrik A/S

Foreword:
This report has been made for explaining the KSA-system more in details and for focussing on
the dewatering of septic sludge with polymer. The report deals with toxicity, heavy metals and
non-environmental substances of polymer.
Conclusion:
The use of polymer in dewatering jobs with the KSA-system are no threat to the recipient for the
following reasons:
- The polymer will not reach the recipient because if small polymer residuals remain in the
reject water they will bind with the sludge particles remaining in the tank.
- If the polymer by an accident should reach the recipient the polymer will quickly
biodegrade
- The adding of heavy metals through polymer is insignificant
- The adding of non-environmental substances through polymer is insignificant.
- The polymer can not pass biomembranes and has for that reason no toxicity for any living
creatures.

Contents:
3
Page
1. About the KSA system.........................................................................................................1
2. Polymer (polyelectrolytes)...................................................................................................2
References
2.1 In general about polymer ......................................................................................2
2.2 Heavy metals...........................................................................................................3
2.3 Non-environmental substances.............................................................................3
2.4 Toxicity....................................................................................................................4

1. About the KSA system
The KSA-system is built in a container which is separated in several rooms of various sizes.
In the following the KSA-system is described with a view to the processes taking place during
the cleaning of the water.
- The contents of the septic tank is sucked into the vacuum tank. During this process the
sludge is homogenized. A further homogenizing of the sludge can take place in the
vacuum tank by means of a strong air flow.
- The homogenized contents of the vacuum tank is pumped into the dewatering tank and
during this process polymer in exact quantities is added. The polymer solution (max.
0,5% w/w solution) is stored in the polymer tank, which contains a stirring device. The
quantity of the polymer is dosed by means of an adjustable dosing pump. The amount of
polymer to be dosed is estimated by means of both visual and physical methods made by
a test sample drawn from the test cock.
- The testing is important because if the dosing is too high or too low the result of the
dewatering will be bad. Furthermore a dosing which is too high will be uneconomical
because of the higher consumption of polymer and the extra cleaning of the dewatering
filters.
Polymer and sludge is mixed thoroughly resulting in the best possible dewatering.
The adding of polymer results in coagulation of the sludge particles and in a separation of
water and particles. The water runs through the dewatering filters (size of the mesh is
7ooFm) and runs to the rejectwater tank. During the dewatering process no pressure,
compression or vacuum takes place, and because of this the rejectwater is extremely clean
in comparison with rejectwater obtained from other dewatering systems.
- The septic tank is filled with the rejectwater resulting from the dewatering process, this
preserves the biological activity in the septic tank. The rejectwater which is going back
originates from the septic tank which has just been emptied. If small polymer residues
remains in the reject water they will bind with the sludge particles always remaining in
the septic tank. In this way it is ensured, that the polymer will not be let out in the
receipient.
- After emptying, dewatering and returning of the cleaned water the process can be
repeated with a new septic tank.
- When the working day has ended the dewatered sludge can be emptied in an approved
depositing place (an approved dump site or an waste water treatment plant)
The advantage of the KSA-system is that septic sludge can be treated individually (depending on
the condition of the sludge) by changing the type and the amount of polymer. The system will
furthermore homogenize the sludge which makes it easier to dose it with the correct amount of
polymer. Furthermore the system makes it possible to empty septic tanks all day long without
having to empty the system. In this way transport time and fuel consumption is reduced. All

things considered a very good environmental solution.
2. Polymer (polyelectrolyte)
Polymer is an organic dewatering aid with a high molecular mass, based on polyacrylicamide.
Polymers are in three groups:
a) Nonionic polymer
b) Anionic polymer
c) Cationic polymer
2.1 In general about polymer
The charges of the polymers will bind very strongly to particles with the opposite charge. As
polymers are long molecule groups a lot of particles will be bound to a polymer molecule. It
results in the formation of large colloids (flocs), separating water and suspended solids. The
water which has been separated will now only contain solutions. The flocculation does not
happen by means of a chemical reaction, but by means of a physical reaction, where negative
particles attract positive particles and vice versa. The active polymer is accumulated in the sludge
/2/.
Polymers have a high affinity for solid surfaces, and absorb strongly and irreversibly. Therefor, it
is highly unlike that they will pass through a sewage-treatment process, but will be absorbed by
the biomass and other suspended matter and thus be fully removed from the sewage before
discharge, reporting ultimately in the sludge. /1/
Polymers and co-polymers are stable when pure, but they are quickly biodegradable when mixed
with water.
Nonionic polymer
The nonionic polymers are molecules with a neutral charge, they usually react with particles
being either faintly cationic or faintly anionic. A nonionic polymer is typically used for sludge of
acid reaction or sludge from the paper industry.
Nonionic polymer is technically polyacrylamides with neutral charges. The polymer is obtainable
both as granulate and as emulsion.
Anionic polymer
The anoinic polymers are molecules with a negative charge and will react with sludge particles
with a positive charge. An anoinic polymer must therefore be applied to a sludge type with a
positive charge - typically chemically precipitated sludge and industrial sludge.
Anionic polymers are co-polymers of acrylamide with increasing contents of acrylic groups,
which give the polymers their negative charges. The polymer is obtainable both as granulate and
as emulsion-. /9/

Cationic polymers
The cationic polymers are molecules with a positive charge and will react with sludgeparticles
with a negative charge. A cationic polymer must therefore be applied to a sludge type with a
negative charge - typically sludge from septic tanks, and from mechanical and biological sewagetreatment
plants.
Cationic polymers are co-polymers of acrylamide with increasing amount of cationic comonomeres.
The polymer is obtainable both as granulate and as emulsion. /9/
2.2 Heavy metals
Research has both shown certain heavy metals in polyelectrolytes and found the contents
negligible. The adding of heavy metals to the sludge through the polyelectorlytes is insignificant.
/2//3/.
Research has shown that the contents of heavy metals in the reject water often are below the limit
of detection. The very low contents of heavy metals in the reject water is a.o. due to:
- the very low contents in the polymer
- strong adsorption from the polymer
- formation of complexes of colloid particles during the
dewatering /10/
- the construction of the dewatering tank gives the sludge
filtrating characteristics
2.3 Non-environmental substances
The contribution to the contents of non-environmental organic substances in the sludge are
insignificant /2/
On this basis it is likely that there are no substantial environmental problems involved when the
products in question are applied in sludge dewatering /2/
A unique definition of the non-environmental organic substances is difficult, but seen in the light
of a similar American list with 192 substances, Sweden and Norway have made a list of priority
pollutants, comprising 70 non-environmental substances /4/.
Priority pollutants have been selected both because of their dangerousness to the environment
(toxicity, degradability and bio accumulation) and from the high frequency in use and occurence
/4/.
With a dosing of polymer at an average of 2,5 g/kg dry solids the polymer will give 0,045 Fg
chlorobenzenes/kg dry solids sludge and 0,625 Fg trichlorethane/kg dry solids sludge.

The contents of non-environmental substances in the reject water will typically be even less than
in the dewatered sludge, as these substances are mainly bound to the particles in the sludge. This
is a.o. due to:
- a very low contents in the polymer
- strong adsorption from the polymer
- the construction of the draining tank gives the sludge
filtrating characteristics.
2.4 Toxicity
Research (/5/, /6/, /7/, /8/) of polyacrylamide and acrylamide with at view to the toxicity, biodegradability
etc. shows the following:
The toxicity of polyacrylamide originates from the contents of acrylamide.
The researches agree that the toxicity of polyacrylate is very low. The polymer itself is not toxic
as it cannot pass biomem-branes.
Acrylamide-monomers have a high water solubility and are biodegradable in anaerobic or
aerobic, light or dark conditions.
A bio-concentration and accumulation of acrylamide in the food chain is not likely.
Based on the knowledge which has been gathered now, one can conclude that there are no
negative effects on the environment due to the use of polyelectrolytes in sewage-treatment plants
or by using the dewatered sludge on farmland /7/.
The use of polyelectrolytes in sludge dewatering is unproblematic seen on this basis.

1/ Allied Colloids
Pollution Control Division
"Technical and Processing Data for
Zetag and Magnafloc".
/2/ Miljøministeriet Miljøstyrelsen
Miljøprojekt nr. 255.
"Fældningskemikaliers indhold
af miljøfremmede stoffer", 1994
References:
/3/ Metaller i kommunalt avloppavatten.
Rapport NSV PM 1942.
Naturvårdsverket og Svenska Vatten- och Avlopsverksforening, 1985.
/4/ "Slam - Innhåll av organiske miljöfarliga ämnen".
NSV - rapport 4085.
Statens Naturvårdsverk, Sverige,1992
/5/ Acrylamide and Polyacrylamide: A Review of Production, Use, Environmental Fate and
Neurotoxicity.
Eldon A. Smith and F,W. Oehme. Kansas State University, USA.
Rev. Environ. Health, Volume 80 - 1989.
/6/ Toxicity of Polyacrylamide and Acrylamide Monomer.
Diana J. King, Richard R. Noss.
University of Massachusetts, USA.
Rev. Environ. Health, Volume 80, 1989.
/7/ Auswahl und Einsatz von organischen Flockunsthilfsmitteln - Polyelectrolyten - bei der
Klärschlammentwasserung. Arbejdsrapport fra ATV/BDE/VKSudvalg 3.2.
ATV-Arbeitsberichte, 4/1992.
/8/ Der einfluss von Polymeren auf die anaerobe Schlammfaulung und die Entwasserbarkeit
von Faulschlammmen. Helmut Kapp.
Gwf-wasser/abwasser 126, 1985.
/9/ Hüls: High tech polymer
Hüls Danmark A/S, 01.05.1995
/10/ Kemiske stoffer i landjords miljøer.
Arne Helweg, Teknisk Foelag A/S, 1988