Presentation on theme: "Waste Water Treatment in Sweden Kerstin Mundt 2006."— Presentation transcript:
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
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
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/L Nitrogen 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 EU Limits 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…
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 m 3 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)
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
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