Waste Water Treatment in Sweden

Kerstin Mundt 2006

History of waste water treatment

• 1920: all towns had waste water piping but only one had treatment

• 1950’s biological treatment (to reduce bad smell)

• 1955: law to treat waste water

• 1960’s: problem with over fertilization in lakes caused by phosphorus. Treatment started

• 1970’s finacal aid to build phosphorus treatment

• Around 1985: problem with nitrogen, treatment started

History of waste water treatment

Improvement of treatment

Sweden today

• 2000 public waste water treatment plants with 7.7 milj. people connected

• 1.3 milj. people have private treatment• Pollution of water courses from

wastewater on the same level as 100 years ago

• Problem 1: Treatment in small plants and private treatment (phosphorus)

• Problem 2: Sludge treatment

Level of treatment today

Average degree of purification

Nitrogen BOD

54%

Phosphorus

95% 96%

Laws

The Environmental Code-Ecological harmful activity-General consideration rules (knowledge, technology,

location, raw materials and energy)

”VA-lagen” (water and sewage law)-All municipals have to take care of water supply and waste

water in urban areas

EU-directives-At least secondary, i.e. biological treatment

Permission for Plants over 2000 pe– How much water that can be let out– Level of phosphorus, nitrogen and BOD in

outgoing, cleaned water

Permissions are set individual depending on recipient. Mean values in Sweden :

Phosphorus 0.5 mg/L

BOD 15 mg/LNitrogen 10-15 mg/L (depending on size and location)

Treatment of BOD

• Biological aerobic treatment

• Problem in north part where it is cold Not needed because of much water and few people.

• EU-regulation says all water below 1500 m must be treated.

Treatment of phosphorus

• Problem in fresh water where it is regulating growth.

• Chemical treatment with metal salt(Biological treatment possible, but hard to conrol)

• Hard regulation compared to EULimits in Sweden: 0.3-0.5 mg/l (average outlet 0.3 mg/l) EU-regulation: 1-2 mg/l

Treatment of nitrogen

• Nitrogen is a problem mainly in salt water

• Biological treatment. Nitrification aerobic, denitrification anaerobic

• Problem with EU-regulation-Definition of sensitive water and where treatment is needed

Phosphorus vs Nitrogen

Discussion about Baltic Sea: Improvement of nitrogen treatment unnecessary?

-Fresh water: senstive for phosphorus not nitrogen

-Studies show improvements caused by nitrogen treatment but critics has other explainations

-Waiting for conclusion…

Himmerfjärden waste water treatment plant

Location

Area of uptake

Facts• Run by company, SYVAB, owned by six

municipalties• Started 1974. Today top modern treatment• 250 000 persons connected + 35 000 pe from

industry• Average flow 110 000 m3 per day• Purification levels (2003):

– 90% of nitrogen (4.1 mg/l)– 95% of phosphorus (0.31 mg/l)– 97 % of BOD (6.7 mg/l)

Treatment

Treatment

Treatment

Treatment

Treatment

Treatment

Treatment

Treatment

Treatment

Treatment

Treatment

Treatment

Treatment

Deposit

Treatment

Treatment

Treatment

Treatment

Treatment

Treatment

Use of sludge

• 26 000 ton/year (2003) 6100 ton dry substance

– 80% cover landareas (deposits, parks etc.)– 20% deposit (forbidden since 2005)– 1.5 % fertilizing of forest (test)– 0.5 % burned (test)

• Need to find long lasting solution

Sludge problem in Sweden

• 1 000 000 ton sludge produced every year– 2.8 % phosphorus, 3.8 % nitrogen good fertilizer

• Fertilizer on fields best use from ecological and recycling point of wiew– Problems: chemicals, heavy metalls– Limits set by Swedish environmental protection agency – How do we know what is harmful? (flame retardants etc)

• Examples of alternatives: Biosoil, fertilizer for energy forest and real forest, burning

• Long lasting solution and regulations is needed

Conclusions

• Good public waste water treatment

• Small treatment plants and private treatment a problem

• Rules for how sludge should be treated is needed