KENYA STANDARD  KS2767 -13:2022 
ICS ##.### 
1st  Edition  
  
 © KEBS  2022  
 Wastewater treatment plants —  
Part 13: Chemical treatment — 
Treatment of wastewater by  
precipitation/flocculation  
 
 
  
 TECHNICAL COMMITTEE REPRESENTATION  
The following organizations were represented on the Technical Committee:  
1. CSI International ltd  
2. Dousg lobal Management solutions  
3. Ecosave Africa Ltd  
4. Embu Water and Sanitation Company LTD  
5. Environment Institute of Kenya  
6. Green Kenya Investment Corporation  
7. Jomo Kenyatta university of agriculture and technology  
8. KenGen PLC  
9. Kenya Chemical Society  
10. Kenya water Insti tute 
11. Kenyatta university  
12. Nairobi City Water and Sewerage Company  
13. National Environment Management Authority  
14. National Public Health Laboratory  
15. Ministry of Transport, Infrastructure, Housing, Urban Development and Public Works  
16. Synergy Ltd  
17. Taita Taveta Univers ity 
18. TANATHI Water Works Development Agency  
19. United States International University -Africa  
20. Kenya Bureau of Standards — Secretariat  
REVISION OF KENYA STANDARDS  
In order to keep abreast of progress in industry, Kenya Standards shall be regularly reviewed.  Su ggestions 
for improvements to published standards, addressed to the Managing Director, Kenya Bureau of Standards, 
are welcome.  
© Kenya Bureau of Standards, 2021  
Copyright. Users are reminded that by virtue of Section 25 of the Copyright Act, Cap. 130 of 2001 of the Laws of Kenya, copyright 
subsists in all Kenya Standards and except as provided under Section 25 of this Act, no Kenya Standard produced by Kenya Bure au of 
Standards may be reproduced, stored in a retrieval system in any form or transmitted by any  means without prior permission in writing 
from the Managing Director.KS 2767 -13:2022 
  
Wastewater treatment plants —  
Part 13: Chemical treatment — 
Treatment of wastewater by precipitation/flocculation  
Kenya Bureau of Standards, Popo Road, Off Mombasa Road,  
P.O. Box 5497 4 - 00200,  Nairobi, Kenya  
 +254 020 6948000, + 254 722202137, + 254 734600471  
 info@kebs.org  
 @KEBS_ke  
 kenya bureau of standards (kebs)   
 Foreword  
 
This Kenya Standard was prepared by the Water and Sanita tion Technical  Committee under the guidanc e of 
the Standards Projects Committee, and it is in accordance with the procedures of the Kenya Bureau of 
Standards . 
 
During the preparation of this standard, reference was made to the following document (s):  EN 12255 :  
Wastewater treatment plants — Part 1 3: Chemical treatment — Treatment of wastewater by 
precipitation/flocculation . 
 
Acknowledgement is hereby made for the assistance derived from this (these) source (s)  
The parts of these series are as follows:  
– Part 1: General construction principles  
– Part 3: Preliminary treatment  
– Part 4: Primary settlement  
– Part 5: Lagooning processes  
– Part 6: Activated sludge processes  
– Part 7: Biological fixed -film reactors  
– Part 8: Sludge treatment and storage  
– Part 9: Odour control and ventilation  
– Part 10: Sa fety principles  
– Part 11: General data required  
– Part 12: Control and automatization  
– Part 13: Chemical treatment  
– Part 14: Disinfecti on 
– Part 15: Measurement of the oxygen transfer in clean water in activated sludge aeration tanks  
– Part 16: P hysical  (mechanical) filtration ) 
 
 KENYA STANDARD  KS 2767 -13:2022 
 
 © KEBS  2022  
 Wastewater treatment plants — Part 13: Chemical treatment — 
Treatment of wastewater by precipitation/flocculation  
 
1 Scope  
 
This Standard specifies the requirements for chemical treatment of wastewater by precipitation/flocculati on for 
removal of phosphorus and suspended solids.  
 
The application of polymers is not described in this Standard.  
 
2  Normative references  
 
This Standard incorporates by dated or undated reference, provisions from other publications. These 
normative referen ces are cited at the appropriate places in the text, and the publications are listed hereafter. 
For dated references, subsequent amendments to or revisions of any of these publications apply to this   
Standard only when incorporated in it by amendment or r evision. For undated references the latest edition of 
the publication referred to applies (including amendments).  
 
EN 752 -6, Drain and sewer systems outside buildings — Part 6: Pumping installations.  
 
KS 2766 , Wastewater treatment — Vocabulary.  
 
EN 10088 -2, Stainless steels — Part 2: Technical delivery conditions for sheet/plate and strip for general 
purposes.  
 
KS 2767 -1, Wastewater treatment plants — Part 1: General construction principles.  
 
KS 2767 -6, Wastewater treatment plants — Part 6: Activated sludge  process.  
 
KS 2767 -11, Wastewater treatment plants — Part 11: General data required.  
 
EN 12518:2000, Chemicals used for treatment of water intended for human consumption — High-calcium 
lime.  
 
3  Terms and definitions  
 
For the purposes of this Standard, the t erms and d efinitions given in KS 2766  and EN 12518:2000  
and the following apply.  
 
3.1 
chemical treatment of wastewater  
treatment of wastewater by chemical coagulation/precipitation with metal salts (including lime) or organic 
polymers in order to remove in organic and organic phosphorus compounds and suspended solids and colloids  
 
4  Requirements  
 
4.1          General  
Chemical treatment of wastewater can be divided into two processes: a reaction phase, that consists of 
precipitation of dissolved phosphates, de stabilisation of colloids and the formation of flocs, and a separation 
phase, in which the flocs are separated from the water.  
  
2 © KEBS  2022 – All rights reserved  
 The reactors and floc separators (sedimentation tanks, flotation units etc.) for the chemical treatment can be 
integrated with t he other parts of the wastewater treatment plant (pre -precipitation, simultaneous precipitation, 
see 4.2.2.2 and 4.2.2.3) or be a separate part of the treatment plant (post precipitation, direct precipitation).  
 
The water level in the chemical reactors and  tanks may be controlled by fixed or adjustable weirs. It is 
particularly important where there are multiple parallel reactors.  
 
The design of the process shall take into account variations in flow and load as stipulated in KS 2767 -1 and  
KS 2767 -11. 
 
4.2 C hemical background and process options  
 
4.2.1  Chemical process  
 
In order to obtain coagulation/precipitation a cationic chemical has to be added to the wastewater. Most 
commonly this is a salt of aluminium or iron , and cationic polymers . Lime may also be used. I f only 
coagulation (removal of particles) is aimed at, a cationic polymer may be added alone or in addition to a metal 
salt. 
 
Phosphorus can be present in the wastewater in the following forms:  
 
a) organically bound phosphorus,  
 
b) inorganic phosphorus,  
o polyphos phate,  
o orthophosphate.  
 
Polyphosphates are eventually converted to orthophosphates and the organically bound phosphorus is 
converted to orthophosphate during biological treatment.  
 
In primary treatment, phosphorus fixed to settleable particles is removed ( 5 % to 15 % of the total influent  
phosphorus depending on the character of the wastewater). In the biological treatment a certain amount of  
phosphorus is consumed at the microbial synthesis of new cellular material (10 % to 30 % of the influent  
phosphorus) . By introducing an anaerobic stage where volatile fatty acids are produced and phosphates are 
released an increased biological removal of total phosphorus can be reached without addition of chemicals 
(60 % to 90 % of the influent concentration).  
 
In the c hemical precipitation, a precipitation agent (such as aluminium sulphate, ferrous sulphate, ferric 
chloride or calcium hydroxide) is added to the wastewater. The orthophosphate phosphorus is precipitated as 
metalorthophosphate. Al3+ and Fe3+ also form coll oidal hydroxides. The solubility of the precipitates is pH -
dependent.  
 
Organic polyelectrolytes are used as flocculation agents for colloidal and suspended matter.  Organic polymers 
may be used as primary coagulants as well as in the more traditional floccu lation step of binding already 
formed small flocs into larger particles. The polymer acts as a destabilising agent via a charge 
neutralisation/precipitation mechanism, and is also an agent for floc growth.  
 
Chemical coagulation/precipitation can be carried  out in six different ways, namely  
o direct precipitation,  
o pre-precipitation,  
o simultaneous precipitation,  
o post-precipitation,  
o multipoint precipitation,  
o precipitation on filters.  
 
4.2.2 Precipitation processes  
 
4.2.2.1 Direct precipitation  
 
Direct precipitati on is used in wastewater treatment plants without a biological stage.  KS 2767 -13:2022 
© KEBS  2022 – All rights reserved  3 
  
In a direct precipitation plant, the precipitation agent should be added after the preliminary stage (screen, grit 
chamber and possibly a primary settlement tank).  
 
The precipitation ag ent should be added in a way that assures rapid and complete mixing of the chemical.  
After mixing flocculation takes place in a flocculation tank. The chemical flocs are then separated in a final  
sedimentation tank or another floc separation device.  
 
4.2.2 .2 Pre -precipitation  
Pre-precipitation can be used in wastewater treatment plants having both mechanical and biological 
treatment.  
 
With pre -precipitation, the addition of the precipitation agent is effected before the biological stage, often 
before the ae rated grit chamber, pre -aeration tanks, or flocculation tanks. The chemical flocs are separated 
together with the primary sludge in the primary settlement tanks.  
 
Chemical flocs which are not removed in the primary settlement tank are transported with the wastewater and 
separated in the secondary settlement tank together with the biological sludge.  
 
4.2.2.3 Simultaneous precipitation  
 
Simultaneous precipitation can be used in wastewater treatment plants with biological treatment depending on 
the activated s ludge process used.  
 
With simultaneous precipitation the addition of the precipitation agent is effected in the aeration tank, at the 
end of the aeration tank or together with the return sludge, where both a biological and a chemical process 
takes place.  
 
The mixed biological and chemical sludge is separated in the secondary settlement tank or a flotation unit. 
The return sludge, the excess sludge and the mixed liquor suspended solids contain a larger part of inorganic 
material as compared to the sludges in  a normal activated sludge plant.  
 
4.2.2.4 Post -precipitation  
 
Post-precipitation can be used in wastewater treatment plants with biological treatment (activated sludge, 
trickling filter etc.).  
 
With post -precipitation the addition of the precipitation age nt is done in a mixing tank after the secondary  
settlement. Floc formation takes place in a flocculation tank followed by a final clarification tank where the 
chemical sludge is separated. Alternatively, lamella sedimentation or flotation can be used for s eparation.  
 
4.2.2.5 Multipoint precipitation  
 
The efficiency of the precipitation may be increased by adding the chemicals at two or three different points, e. 
g. the grit chamber, the aeration tank, the final sand filter.  
 
4.2.2.6 Precipitation on physica l filters  
 
Precipitation on filters is normally a complement to biological phosphorus removal or to a pre -precipitation or a 
simultaneous precipitation. The chemical is added in the channel or pipe leading to the filter. An effective 
mixing shall be arrang ed. 
 
4.2.3 Selection of precipitation chemicals  
 
Details of chemicals often used are given in annex A. Apart from that some waste products or by -products and 
products ready for use can be used as precipitation or flocculation chemicals.  
 
Careful considerat ion of the heavy metal concentration and other pollutants shall be made.  
 
NOTE Details about limits can be obtained from relevant national and legislation.   
4 © KEBS  2022 – All rights reserved  
  
 
 
 
Table 1 — Normal use of chemicals  
 
 Al-sulphate  Polyaluminium  
chloride  
 Ferrous  
sulphate  
 Ferric  
chloride  
 Lime  
 Cationic 
polymer  
Direct 
precipitation  x  x  - x  x 
 
 x  x 
Pre-
precipitation  
 x  x  x  x  x x 
Simultaneous 
precipitation  
 x x  x  x  - x 
Post -
precipitation  
 x  x  -  x  x x 
Multipoint 
precipitation  
 x  x  (x)  x  x x 
Precipitatio n 
on filters  x x x x - x 
 
The different precipitation chemicals have different pH -optima (see annex A). The addition also influences the 
pH of the water.  
 
Type and dose of the chemical is dependant on the type of wastewater and its content of bicarbonate . They 
should both be determined in a precipitation test.  
 
On the specific wastewater, this test may be done in beakers equipped with stirrers with variable velocity or in 
pilot or full -scale trials.  
 
 
4.3 Storage of chemicals  
 
4.3.1 General  
 
The manufactu rers directions shall be observed.  
 
The following issues shall be considered:  
 
o safety precautions in handling chemicals (e. g. protective goggles, respiration masks etc.);  
 
o maximum storage time of chemical;  
 
o safety precautions to contain leakage of full ta nk volume;  
 
o material data sheet  
 
o housing  
 
o climatic conditions.  
 
o For safety precautions see also KS 2767 -10. 
 KS 2767 -13:2022 
© KEBS  2022 – All rights reserved  5 
 4.3.2 Aluminum salts  
 
4.3.2.1 Aluminium sulphate  
 
Granulated aluminium sulphate in dry form is not corrosive and can be stored in contact with all types of  
construction materials. A silo for storage has to be completely tight to avoid humidity.  
 
Solutions of aluminium sulphate are acidic and corrosive and the construction material should be appropriate 
plastic or stainless steel of suitable quality w ith minimum Molybdenum content of 2 % (e. g.  1.4571 
(X6CrNiMoTi 17 -12-2) in accordance with EN 10088 -2).  
 
4.3.2.2 Polyaluminium chloride  
 
The solutions are acidic and corrosion proof material as appropriate should be used (plastic or rubber -covered 
steel) . 
 
4.3.3 Iron salts  
 
4.3.3.1 General  
 
Iron based precipitation chemicals can be produced of by -products.  
 
4.3.3.2 Ferrous sulphate (monohydrate)  
 
The dry granulate of ferrous sulphate is not corrosive. Silos for storage shall be completely tight to avoid 
humidity.  
 
Solutions are corrosive and shall be stored in tanks of stainless steel (e. g. 1.4571 (X6CrNiMoTi 17 -12-2) in 
accordance with EN 10088 -2) or appropriate plastic.  
 
4.3.3.3 Ferrous sulphate (heptahydrate)  
 
The green crystaline heptahydrate is acidi c and corrosive. Construction material shall be corrosion proof such 
as stainless steel (e. g. 1.4571 (X6CrNiMoTi 17 -12-2) in accordance with EN 10088 -2), appropriate plastic or 
plastic coated concrete.  
 
Ferrous sulphate (heptahydrate) is not stored in a s ilo but is directly delivered to dissolving tanks in the 
wastewater treatment plant.  
 
4.3.3.4 Ferric chloride and ferric chloride -sulphate  
 
Ferric chloride is acidic and corrosive and shall be stored in corrosion proof tanks such as rubber -covered 
steel or  plastic tanks.  
 
The liquid should not be diluted or aerated.  
 
4.3.4 Calcium salts  
 
Calcium oxide (Quicklime) and calcium hydroxide shall be kept dry.  
 
Calcium hydroxide can be stored in a silo and has good storage capability.  
 
4.3.5 Polymers  
 
 
The Shelf L ife of the polymer coagulant depends on the physical types (ie Dry polymer , Emulsion polymer or 
Solution polymer). Dry polymer has a shelf life of up to 3 years, un -opened bag; Emulsion polymer has a shelf 
life of 6 months when stored in un -opened drum/to te, while Polymer solution shelf life depends of 
concentration and water quality. Polymer should be stored under Storage Temperature: 40 F - 90 F, and   
6 © KEBS  2022 – All rights reserved  
 Emulsion should not be allowed to freeze. Once frozen, thaw in heated area and mix well. During Handling  of 
polymer, always wear latex gloves and eye protection, Minimize exposing to air, avoid dusting (dry polymer),  
Don’t try to clean spilled polymer with water but Use absorbents (vermiculite, sawdust, paper towel, etc.)  
 
 
 
4.4 Dosing equipment  
 
4.4.1 Gene ral 
 
Unless otherwise specified, the dosing system shall have some form of back -up, either built in or held in 
storage.  
 
Where automatic controls are used, the system shall be designed to change into safe state (fail safe mode) in 
case of failure. In the m ajority of cases, the reaction between the chemicals and the wastewater is extremely 
rapid. It is therefore important that the precipitation agent is distributed uniformly throughout the entire 
waterbody. This can be done in many ways, e. g. with injection  or mixing systems.  
 
The design should include provisions for removal of scaling.  
 
General requirements for dosing equipment that are not included in 4.4 may be specified in accordance with 
national standards.  
 
4.4.2 Aluminium salts  
 
4.4.2.1 Aluminium sulp hate technical grade  
 
This salt can be fed dry but is normally dissolved in water. A normal mass fraction is 10 % to 15 %. The  
concentration shall be higher than 5 % in order to avoid precipitation of metal hydroxide.  
 
The velocity in pipes should not be l ower than 0.5 m/s in order to avoid precipitation on the pipe surface.  
 
4.4.2.2 Polyaluminium chloride  
 
Technical polyaluminium chlorides are dosed directly from storage tanks. The solution is acid and corrosion 
proof pumps shall be used. Pipes and valves should be made of rubber -covered steel or appropriate plastic.  
 
4.4.3 Iron salts  
 
4.4.3.1 Ferrous sulphate (monohydrate)  
 
The granules are normally dissolved in water. They are dosed with a screw to the dissolving tank. The 
dissolving equipment has to be d esigned to avoid clogging.  
 
4.4.3.2 Ferrous sulphate (heptahydrate)  
 
The bulk chemical ferrous sulphate (heptahydrate) is dissolved in a suitable tank e. g. of glass -fibre reinforced 
polyester. A precipitation can occur and the solution may need to be filt ered before the dosing.  
 
It is normally dosed as a saturated solution. Aerosols of ferrous sulphate solution attack tooth material and a 
safety mask should be used when mixing is achieved using aeration.  
 
4.4.3.3 Ferric chloride  
 
Ferric chloride solution is dosed directly (without dilution) from the storage tanks. The pumps shall be 
corrosion proof. Pipes and valves shall be corrosion proof and made of appropriate plastic or rubber -covered 
steel.  
 
4.4.4 Calcium salts  KS 2767 -13:2022 
© KEBS  2022 – All rights reserved  7 
 Calcium oxide has to be slaked in a lim e slaker and is then mixed with water to a lime slurry that is fed to the 
wastewater by a dosing pump.  
 
Calcium hydroxide is typically dosed with a screw feeder at the bottom of the lime silo. The dry lime is mixed 
with water in a mixing tank and fed to th e wastewater by a dosing pump. There is a risk of clogging of pipes.  
  
Therefore the pipework shall be designed for easily cleaning and consideration should be given to  
 
o constant circulation;  
o a flushing system.  
 
An alternative is to use rubber that are mov ed frequently to avoid clogging.  
 
4.5 Silos and tanks  
 
The silos or storage tanks should be placed near the dosing point of the chemicals. Pipe length should be as 
short as possible, and the pipework should be designed without any stagnation zones or sharp  bends, 
especially when slurries (lime) or dissolved chemicals (e. g. aluminium sulphate) are used.  
 
4.6 Mixing systems  
 
The mixing system shall be capable of a rapid and uniform distribution of the chemical in the wastewater.  
Provision should be made for easy removal of the mixing devices without emptying the tank. The choice of the 
device depends on the characteristics of the wastewater to be treated.  
 
4.7 Flocculators  
 
Where flocculators are needed, the hydraulic design shall minimise short circuiting. T he distance between the 
flocculator and the separation unit (sedimentation tank, flotation) shall be short and the velocity of water 
flowing to the separator should be < 0.10 m/s.  
 
It is important that the water leaving the flocculation process should not be subjected to greater shear forces 
than encountered in the flocculation process. Therefore, the flocculation unit should be situated directly 
adjacent to or in the sedimentation tank.  
 
4.8 Sedimentation tanks  
 
4.8.1 General  
 
The sedimentation tanks shall  adequately separate the chemical sludge solids from the effluent and provide a 
concentration zone for withdrawal of sludge. The efficiency of separation affects the quality of the final 
effluent.  
 
Sedimentation tanks may be of upward flow type, horizontal  flow type or a lamella separator.  
 
4.8.2 Design considerations  
 
Design requirements are found in KS 2767 -1 and KS 2767 -6. 
 
4.8.3 Chemical sludge wasting  
 
Sludge wasting involves removing the chemical sludge formed during the precipitation process.  
The wei ght and volume of sludge to be wasted, depends primarily on the pollution load and the type of 
chemical used.  
 
Sludge wasting shall be as regular as possible taking into consideration further sludge thickening and/or 
treatment.  
  
8 © KEBS  2022 – All rights reserved  
 Specifications in raw waste water pumping installations according EN 752 -6 and general construction 
principles according KS 2767 -1 are applicable to the excess sludge wasting system.  
 
4.9 Flotation  
 
In flotation tanks air is used to float particles to the surface, where they can be s eparated as sludge. The 
flotation should be of dissolved -air flotation type. The surface sludge is collected by a surface scraper. In 
addition, there should be a collection system for the heavy sludge settled on the bottom of the tank.  
 
Flotation is also d escribed in KS 2767 -8 
. 
4.10 Physical filtration  
 
Filtering is normally used only as a complement to sedimentation and flotation in order to provide a better  
suspended solids removal. However, some types of filters are designed to be able to serve as the o nly 
separation stage necessary for chemical treatment of wastewater.  
 
If sand filters are used as the only stage for separating chemical flocs from the wastewater, there shall be a 
primary settling step before the chemical treatment. Where lime is used as a precipitation agent, physical 
filtration is not appropriate.  
 
Physical filtration is described in [3]  
. 
4.11 Sludge  
 
4.11.1 Sludge production  
 
In practical operation the sludge production can be different. It can be determined by precipitation tests.  
 
The chemical precipitation with metal salts produces a mixed phosphate hydroxide sludge.  
Typical relations are:  
 
o 1 g Al produces 4 g suspended solids;  
o 1 g Fe produces 2.8 g suspended solids;  
o 1 g Ca produces 0.7 g suspended solids.  
 
 
4.11.2 Sludge characteris tics 
 
The sludge flocs are fragile, especially the aluminium -hydroxide -phosphate flocs.  
 
Iron-phosphate sludge has better settling and thickening characteristics than aluminium -phosphate sludge and 
forms a more compact sludge. Calcium -phosphate sludge sett les rapidly and forms a compact sludge. In 
order to improve the sludge thickening and dewatering, polymers may need to be added.  
 
5. Disposal of final precipitate  
 
The final precipitate shall be disposed in accordance to National Environmental Management Authority 
guidelines.  
 
Annex A  
(normative)  
Precipitation chemicals  
 
A.1 Aluminium salts  
 
Aluminium salts suitable for chemical precipitation of phosphorus are   
Aluminium sulphate Al 2(SO 4)3 - 14 to 18 H 2O 
 KS 2767 -13:2022 
© KEBS  2022 – All rights reserved  9 
 The technical grade also contains iron as Fe 2(SO 4)3 - 9H2O. The product is granulated. The pH -optimum is 
from 5.7 to 6.5.  
 
― Polyaluminium chloride Al n(OH) mCl3n-m 
 
The technical grade also contains iron. The product is liquid. The density is 1.3 g/cm3 
 
The pH -optimum is from 5.7 to 8 (the interval is depend ed on basicity of the chemical and the hardness of 
water).  
 
A.2  Iron salts  
 
A.2.1 Ferrous salts  
 
Ferrous sulphate, monohydrate FeSO 4 -  H2O 
Ferrous sulphate, heptahydrate FeSO 4 - 7 H 2O 
A.2.2 Ferrous sulphate, monohydrate  
 
The technical grade is granulated  (0.2 mm to 3 mm) and contains 87 % mass fraction to 88 % mass fraction  
FeSO 4 . H2O. The pH -optimum is > 6.5 (conversion to ferric ions and flocculation).  
 
A.2.3 Ferrous sulphate, heptahydrate  
 
The technical grade is light green with a structure like snow.  
 
It contains about 90 % mass fraction FeSO 4 - 7 H 2O. The pH -optimum is > 6.5 (conversion to ferric ions and 
flocculation).  
 
A.2.4 Ferric salts  
 
Ferric chloride, solution of FeCl 3. 
 
The pH -optimum is from 4.5 to 6.5 or > 8.5.  
 
The widely used technical gra de contains Ferric chloride -sulphate with a Fe3+ concentration of 11.6 % mass 
fraction. It has successively been replaced by a product with lower content of heavy metals and a Fe3+ 
concentration of 13.7 % mass fraction. This product should be used if possi ble. 
 
A.3 Calcium salts  
 
A.3.1 General  
 
Direct precipitation or post -precipitation can be made with calcium hydroxide Ca(OH) 2 or calcium oxide 
(normally granulated) CaO.  
 
The pH -optimum is from 9.3 to 11.2 (according to the effluent concentration required) . 
 
A.3.2 Calcium oxide  
 
The fractions are: < 0.2 mm, < 2 mm, 2 mm to 12 mm and 12 mm to 25 mm.  
 
The finest fractions (< 0.2 mm, < 2 mm) are creating dust and are delivered in tank cars or tank railroad cars.  
 
Calcium oxide is very aggressive. Mixing with w ater creates alkaline calcium hydroxide and heat.  
 
A.3.3 Calcium hydroxide  
 
Calcium hydroxide is manufactured from calcium oxide by adding the stoichiometric amount of water. The 
calcium hydroxide is a fine powder (99.5 % finer than 0.2 mm and 97.5 % finer  than 0.09 mm).  
  
10 © KEBS  2022 – All rights reserved  
 Calcium hydroxide is aggressive and personal protection equipment (protection goggles, respiration mask, 
gloves etc.) shall be used.  
 
A.4 Polymers  
A.4.1 General  
 
A.4.2 Dry Polymer  
 
This is either Cationic, anionic, or non -ionic. The  Molec ular weight: up to 10 M (cationic), up to 20 M (anionic, 
non-ionic). Dry polymer is up to 90% active with Polymer particle size: 0.1 - 2 mm. The cost for dry polymer is 
high 
 
A.4.3 Emulsion Polymer  
 
This is either Cationic, anionic, non -ionic with Molecula r weight: up to 10 M (cationic), up to 20 M (anionic, 
non-ionic). It is  30 - 60% active, and  Polymer gel size: 0.1 - 2 μm. the cost for dry polymer is high  
 
A.4.4 Solution Polymer (Mannich)  
 
This is Cationic only with molecular weight up to 10 M. Solutio n polymer is  4 - 6% active, is low in cost and 
has Limited usage  
 
.KS 2767 -13:2022   
 
© KEBS  2022– All rights reserved   
  