Groundwater, its treatment and protection Harri Mattila, 2019 1 - - PowerPoint PPT Presentation
Groundwater, its treatment and protection Harri Mattila, 2019 1 7.10.2019 General l Groundwater forms only 0,53 % of all water resources (worldwide). l In Finland, more than 2/3 of all raw water is groundwater or artificial groundwater l
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l Groundwater forms only 0,53 % of all water
l In Finland, more than 2/3 of all raw water is
l Advantages of groundwater when compared
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l Usually PVC pipe l DN > 50 mm l Screen in the depth
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l optimum situation: no treatment l most common reason is prevention of corrosion l Fe or Mn l organic material l fluoride l salts l radon l arsenic
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l Depends on soil around the
l Sometimes rain water can be acidic l pH of groundwater in Finland is
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l ammonium, nitrate, nitrite, nitrogen l Very rarely in Finnish groundwaters l Usually means pollution by agriculture
l Sometimes also because of wastewater in
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l Can be diluted in groundwater for
l Important factor in corrosion l limit 50 mg/l
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l Most common problems in groundwater
l No health hazard – technical and/or
l Fe < 0,2 mg/, Mn < 0,05 mg/l l Causing also sedimentation in networks
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l Normally because of nearby sea but also
l In nature < 10 mg/l, taste limit 200 – 300
l Very important factor in corrosion
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l Ca- ja Mg –salts l 1 mmol/l = 5,6 º dH l Should be 3 – 5 º dH l The most interesting parameter to
l sometimes high also in Finland, even >10
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l Can be diluted from from the soil (like
l The maximum limit allowed 0,2 mg/l
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l carcinogenic, max allowed 0,01 mg/l l Mainly in deep boreholes l In Finland about 7% of all the deep
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l Max allowed 1,0 mg/l l Is indicating pollution by wastewater l Appears very seldom
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l WHO: max allowed 1,5 mg/l (note,
l Defluoridation is considered as an
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l Max allowed 2,0 mg/l ( an average /
l Rather seldom in groundwater l Mainly because of corrosion in pipelines
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l E.coli is the most important indicator
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l Very difficult to analyze => difficult to
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l Altogether about 70 compounds l Hydrogarbons, alcohols, aethers, esters,
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l Additives in petrol l Are diluted very easily in water => the
l Easy to detect by smell and taste (0,03
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l Hundreds of compounds l Max allowed 0,0005 mg/l (total) l The smallest amounts which can be
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l Mostly in deep wells (in the rock) l No smell, no colour, no taste ! l Radon is the most common one in
l Max allowed 1000 Bq/l)
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l Lack of knowledege concerning health
l Earlier max by WHO 0,15 mg/l, today
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l pH > 7,5 l alkalinity > 0,6 mmol/l l calsium > 10 mg/l l oxygen > 2 mg/l
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l Swamps, springs,
l Humidity changes out
l Old maps might give
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l Seismic sounding l Electrical probing (resistance)
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l Manually l Machinery
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l Most common quality problem with
l Coagulation happens immediately with
l Iron can be removed also biologically
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l In small scales
l Lime stone filtration l Slow sand filtration
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l Water is filtered slowly through a sand
l Surface load 0,05 – 0,2 m/h l Water per one 1 m2: 50 – 200 l/h l Iron content max 1mg/l l Pretreatment could be done by a filter
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l Aeration needed almost always l Dissolved iron is oxidized => can be
l Surface load normally 4 – 5 m/h l Small filters require backwashing more
l Might be expensive ?
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l Generally, ground water is
l Sometimes we have experienced pollution l UV-desinfiction is applicable method for
l UV-desinfection is not affecting the taste
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