THE NWF WATER PURIFICATION PROCESS FRESH WATER IN A NATURAL WAY. Esko Meloni Ferroplan Oy

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1 THE NWF WATER PURIFICATION PROCESS FRESH WATER IN A NATURAL WAY Esko Meloni Ferroplan Oy 1

2 The NWF Water Purification Process: list of contents 1. NWF biological purification of groundwater Iron and manganese in groundwater Removal of iron and manganese from groundwater General Biological methods The NWF process References: municipality of Siilinjärvi and others 2. New development: NWFlo Flotation Process 2

Removal of iron and manganese from groundwater General Biological methods The

3 IRON AND MANGANESE IN GROUNDWATER 3

4 Iron, Fe OCCURRENCE OF IRON IN GROUNDWATER Main form: bivalent soluble ferrous iron, Fe2+, normally as bicarbonate, Fe(HCO3)2 Often also some insoluble trivalent ferric iron, Fe3+, is present as ferric hydroxide, Fe(OH)3 Forms complex compounds with organic and inorganic substances Factors affecting solubility: ph, redox potential, temperature, concentrations of different substances, biological functions 4

hydroxide, Fe(OH)3 Forms complex compounds with organic and inorganic substances Factors affecting

5 OCCURRENCE OF MANGANESE IN GROUNDWATER Manganese, Mn Is present in natural waters in the bi-, tri- and quadrivalent states Main form: bivalent soluble Mn2+ The higher-valent manganese compounds are precipitated as oxides The heptavalent manganese forms soluble purple permanganate, MnO4- Forms complexes with humus in the same way as iron Factors influencing solubility: ph, redox potential, (temperature, concentrations of various substances, biological functions) 5

heptavalent manganese forms soluble purple permanganate, MnO4- Forms complexes with humus in the same way as iron

6 REMOVAL OF IRON AND MANGANESE FROM GROUNDWATER 6

7 Removal of iron and manganese from groundwater 1: Principle General principle: Soluble bivalent iron and manganese compounds are oxidised to insoluble hydroxides (Fe(OH)3) and oxides (MnO2) that can be separated by filtering. Oxidisation of iron is easy already around neutral ph. Oxidisation of manganese is more difficult: a higher ph and redox potential is required. The oxidation process is considerably slower and more difficult than with iron. In humus-containing water it can be very difficult. 7

Oxidisation of iron is easy already around neutral ph.

8 Removal of iron and manganese from groundwater 2: Methods Aeration + filtration Oxidation with a stronger oxidant than air (oxygen, ozone, chlorine, permanganate) + fitration Alkalizing filtration Ion exchange Precipitation with iron or aluminium salts + filtration Biological methods Note: all methods involve both chemical and biological activity. 8

fitration Alkalizing filtration Ion exchange Precipitation with iron or aluminium salts

9 Biological removal of iron and manganese from groundwater 1: Mechanisms Two mechanisms: The microbe oxidises iron/manganese biologically thus utilizing the reaction for its living functions and energy economy => biological purification process The microbe precipitates chemically iron/manganese in its cells, mainly on the surface or in its filament, but the precipitated metal is not utilized by the microbe => biologically catalyzed precipitation reaction of iron/manganese 9

purification process The microbe precipitates chemically iron/manganese in its cells, mainly on the surface or in its

10 Biological removal of iron and manganese from groundwater 2: Bacteria Bacteria precipitating iron Biological precipitation: Gallionella ferruginea Mechanical precipitation: families Sphaerotilus and Siderocapsa Bacteria precipitating manganese Manganese only: Pseudomonas manganoxidans Both iron and manganese: several species 10

precipitation: families Sphaerotilus and Siderocapsa Bacteria precipitating

11 Bacteria precipitating iron and manganese 11

12 Biological removal of iron and manganese from groundwater 3: Conditions Iron bacteria function best in the so-called transition state between oxic and anoxic conditions. The necessary rise in redox potential is easily obtained with a small addition of oxygen. Removal of manganese is more difficult than removal of iron; a higher ph and redox potential is required. Furthermore, the manganese bacteria grow more slowly than iron bacteria, and therefore starting manganese removal can take several weeks. 12

The necessary rise in redox potential is easily obtained with a small addition of oxygen.

13 Biological removal of iron and manganese from groundwater 4: Treatment result & filtration The treatment result obtained is better than with chemicals only The iron and manganese sludges produced in the biological process are denser and heavier than chemical sludges. Consequently Removal of water from the sludge is easier Filtration is more effective Washing of the filter can be carried out less frequently 13

in the biological process are denser and heavier than chemical sludges.

14 BIOLOGICAL METHODS Aeration and slow sand filtration: 1900th century Dry filtration (biofilter): 1950 s Aeration + biofiltration + limestone filtration: 1990 s NWF method: 21st century 14

15 Example of techniques: iron and manganese removal at the Rumeland water works in Hamburg, Germany 15

16 THE NWF PROCESS 16

17 The NWF process and its main phases The NWF process is a multi-stage oxidationstripping-biofiltering process with sand filtering as the final treatment stage. Oxidation and removal of acid gases takes place in a single column. Several process steps take place simultaneously or one after another. The metal sludges formed are separated in a sand filter. 17

Oxidation and removal of acid gases takes place in a single column.

18 Description of the aeration process 1. Absorption of the oxidizing gas in the water 2. Sprinkling 3. Fogging 4. Hovering 5. Gas removal under vacuum 6. Chemical reactions on the surfaces of the filler material 7. Biochemical reactions on the surfaces of the filler material 8. Removal of acid gases improves biochemical activity 9. Lengthening of the reaction time 10.Flowing of the water with the hydroxide/oxide sludges and other flocculated substances to the filtering stage 18

Biochemical reactions on the surfaces of the filler material 8. Removal of acid gases improves biochemical activity 9.

19 NWF-PROSESSI 19

20 NWF-LAITOS 20

21 Main effects of NWF treatment Removes effectively iron and manganese, more effectively than chemical methods Reduces the acidity of the water: stripping away carbon dioxide raises the ph of the water by 1-2 ph points and reduces the aggressivity of the water accordingly Removes other dissolved gases, such as methane, hydrogen sulphide (smell!) and radon (radioactivity) Removes organic material and ammonium nitrogen Improves the clarity and freshness of the water 21

22 Advantages of the NWF process in operation Chemicals are not added Saves rinsing water => Low operational costs Small energy consumption Simple to use No clogging problems Simple maintenance Easy to automatize/need of automatizing is little Modular built, easy to install, easy to enlarge EXCELLENT WATER WITH EVEN QUALITY! 22

23 What can happen and often does happen - in a plant using chemicals A large amount of sodium hydroxide was slipped into the drinking water line, a couple was hospitalized. Human error: Forced feed (of the chemical) was forgotten on. I have done these feeds for 15 years, 40 feeds per year, and this was the first time this happened. Water and Soil Iltalehti (Finnish newspaper)

24 EXAMPLE OF A NWF PLANT: MUNICIPALITY OF SIILINJÄRVI 24

25 The Siilinjärvi NWF plant Capacity and purification requirements Flow: continuous production 2000 m3/d, max 200 m3/h Metal contents Raw water Purified water Fe ug/l 50 ug/l Mn ug/l 20 ug/l 25

26 Siilinjärvi treatment results: guarantee trials Iron is removed immediately, measured result 10 ug/l, remains constant Manganese reacts slowly, after 5 months 3 ug/l is reached and remains constant ph~8 Turbidity: none Smells: none 26

27 Siilinjärvi NWF plant Sand fitration Number of fiters 8 pcs. Dimensions D=2200 mm, H=2700mm Three filtering layers Supporting layer on the bottom Alkalizing dolomitic layer in the middle Fine sand layer on top Surface load 3.9 m3/m2/h Washing interval ca. 2 weeks 27

28 NWF REFERENCES Altogether NWF plants have been delivered to Finland, Estonia, Latvia and Norway. 28

29 NEW DEVELOPMENT: NWFLO FLOTATION PROCESS 29

30 NWFlo prefabricated flotationfiltration plants Three sizes, all prefabricated complete plants Small round plant 1 5 m3/h (patent pending) Rectangular plants built in a container Middle-sized 8 20 m3/h (20-feet container) Large-sized m3/h (40-feet container) 30

31 NWFlo round prefabricated flotation-filtration unit 31

32 NWFlo containerized prefabricated flotation-filtration unit 32

Chemistry at Work. How Chemistry is used in the Water Service

Chemistry at Work. How Chemistry is used in the Water Service Chemistry at Work How Chemistry is used in the Water Service WATER TREATMENT Everyday, more than 100 water treatment works in Northern Ireland put approximately 680 million litres of water into the supply