1. The composting of sewage sludge in Tartu Waterworks Ltd Jüri Haller ESTONIA Head of laboratory Sigulda, 24-25 of April, 2008.

2. The requirements for using of sewage sludge in agriculture, in urban landscaping and in recultivation Regulation No 78 of 30.Dec.2002 of the Minister of Environment The sewage sludge considered treated after using aerobic or anaerobic stabilisation methods (incl. composting), chemical or thermal treating or an other methods if the organic matter inside it has not influence on surface- and groundwater, on soil, on flora and fauna and on human health. The sewage sludge considered treated after using aerobic or anaerobic stabilisation methods (incl. composting), chemical or thermal treating or an other methods if the organic matter inside it has not influence on surface- and groundwater, on soil, on flora and fauna and on human health. In meaning of the Regulation No 78 the composting is aerobic degradation process of sewage sludge by the micro- and macro organisms and in adding to the sludge the bark, the straw, the peat or some other bulk materials. The periodical mixing of piles is necessary. In meaning of the Regulation No 78 the composting is aerobic degradation process of sewage sludge by the micro- and macro organisms and in adding to the sludge the bark, the straw, the peat or some other bulk materials. The periodical mixing of piles is necessary. During the process the composting material has to be over 60 0 C at least 6 days During the process the composting material has to be over 60 0 C at least 6 days

3. t 0 and time of exposure required for destruction of some common pathogens and Escherichia coli Most die within 1 hour at 55 0 C and within 15-20 min at 60 0 C Salmonella typhosa No growth beyond 46 0 C; death within 30 min. at 55-60 0 C; 20 min at 60 0 C Salmonella sp. Death within1 hour at 55 0 C and within 15-20 min at 60 0 C Streptococcus pyogenes Death within 10 min. at 54 0 C

4. The composting is the complex series of biological, chemical and physical processes, which needs for successful process some requirements Every composting should have the beginning, ending and monitored intermediate part

5. Requirements for composting Temperature Temperature t 0 indicates the activity of the decomposition process t 0 indicates the activity of the decomposition process Micro-organisms release heat as they feed and grow Micro-organisms release heat as they feed and grow Microbiological activity in the pile is rising about 2 times in every 10 C 0 temperature rising Microbiological activity in the pile is rising about 2 times in every 10 C 0 temperature rising Microbiological activity reduces on too high and on too low t 0 Microbiological activity reduces on too high and on too low t 0 Optimum t 0 inside the pile should be between 45 and 55 0 C Optimum t 0 inside the pile should be between 45 and 55 0 C Pathogens are killed at 50-55 0 C fast Pathogens are killed at 50-55 0 C fast

6. Temperature development inside the composting piles

7. Requirements for composting C N The optimume C/N = 20-30

8. C/N ratio carbon as a source of energy carbon as a source of energy nitrogen for building cell structure nitrogen for building cell structure Organisms that decompose organic matter use

9. The organisms that decompose organic matter are using carbon, as a energy source and nitrogen as crucial component of the proteins in fixed ratio Small C/N ratio (much N) Small C/N ratio (much N) Biological activity of the process is going down Biological activity of the process is going down When the energy source, carbon, is less than that required for converting nitrogen into protein, organisms make full use of the available C and get rid of the excess nitrogen as ammonia. When the energy source, carbon, is less than that required for converting nitrogen into protein, organisms make full use of the available C and get rid of the excess nitrogen as ammonia. Smell! Smell! Too much carbon (C/N is big) Too much carbon (C/N is big) Decomposition slows when the nitrogen is used up and some organisms die Decomposition slows when the nitrogen is used up and some organisms die Other organisms form new cell material using their stored nitrogen Other organisms form new cell material using their stored nitrogen

10. C/N ratio effects on composting

11. Oxygen The micro-organisms need oxygen so air must be able to circulate trough the composting material The micro-organisms need oxygen so air must be able to circulate trough the composting material C 10 H 19 O 3 N + 12,5O 2  10CO 2 + 8H 2 O +NH 3 C 10 H 19 O 3 N + 12,5O 2  10CO 2 + 8H 2 O +NH 3 If a compost heap gets short of air the result is an evil smelling slime If a compost heap gets short of air the result is an evil smelling slime Optimal O 2 content during aerobic composting process is 10-20% Optimal O 2 content during aerobic composting process is 10-20%

12. Mixing of the windrows The mixing period depends of structure and moisture content of the compost Aeration Homogenisation Increase or decrease the moisture content to optimum level

13. Mixing or tuning Turning Mixing and breaking

14. Temperature inside the windrow is uneven Why is important to mix the windrows!

15. Mixing of the windrows You have to mix and pile the raw compost rapidly The first mixing is during the 3-5 days after working up the raw compost Continuously after 5-12 days

16. Moisture content In connexion with intensity of biological degradation process and with compost material structure In connexion with intensity of biological degradation process and with compost material structure The water keeps the thermodynamic balance of the process The water keeps the thermodynamic balance of the process In the composting materials have to be just enough moisture In the composting materials have to be just enough moisture In dry environment the micro organisms will die In dry environment the micro organisms will die Over moisture will turn out the air from the pores of material, sludge turns into the lump and the anaerobic process is taking place Over moisture will turn out the air from the pores of material, sludge turns into the lump and the anaerobic process is taking place The optimum moisture content should be in the range between 50-65% during the composting process The optimum moisture content should be in the range between 50-65% during the composting process

17. pH Important parameter in evaluating microbial environment Important parameter in evaluating microbial environment Optimum pH = 6,5-8,0 during composting Optimum pH = 6,5-8,0 during composting In first few days of composting, the simple organic acids drops the pH to 5 or less. In first few days of composting, the simple organic acids drops the pH to 5 or less. If the degree of aeration is not adequate, anaerobic conditions will occur, the pile pH will drop to about 4,5 and the composting process will be retarded If the degree of aeration is not adequate, anaerobic conditions will occur, the pile pH will drop to about 4,5 and the composting process will be retarded After the temperature reaches a thermophilic stage the pH begins to rise to 8-8,5 and falls in mesophilic stage to 7-8 After the temperature reaches a thermophilic stage the pH begins to rise to 8-8,5 and falls in mesophilic stage to 7-8

18. The bulking materials For the regulation of C/N ratio For the regulation of C/N ratio For guaranteed of needful porosity of compost (aeration) For guaranteed of needful porosity of compost (aeration) Optimum particle size should be between 25-75 mm Optimum particle size should be between 25-75 mm For regulation of moisture content inside the windrow For regulation of moisture content inside the windrow

19. Used bulk materials shredded bark shredded bark woodchips woodchips straw straw peat peat wooden building waste wooden building waste park waste (leaves) park waste (leaves) cardboard chips cardboard chips municipal waste municipal waste bark + peat bark + peat bark + wood ash bark + wood ash straw + bark straw + bark

20. Shredded bark + t 0 is rising quite fast and high + quite good structure + C/N = 110-140 + + easy to get - Unstable quality (structure, moisture, pH, resin) Mature compost needs sieving Sewage sludge:bark = 1:1,5-2,0

21. Woodchips Stable structure Stable structure Good aeration guarantee Good aeration guarantee t 0 is rising fast and stay in high level for a long time t 0 is rising fast and stay in high level for a long time C/N = 250 - 320 C/N = 250 - 320 Dry mat. 50-60% Dry mat. 50-60% Composting material is not diffusive Composting material is not diffusive Sewage sludge:woodchips = 1:1-1,2

22. Wooden building waste + cheaper as bark + dry mat. 80-85% + C/N ~ 200 + richer of minerals -Inadvisable supplements may occur -Unstable structure Sewage sludge:building waste = 1:1,5-2,0

23. The straw + After the mixing of pile the windrow is very airy + t 0 is rising very fast + C/N = 85 - 100 + dry mat. 55-65% + high potassium content - The sludge content in the pile is very small - The braking of straw balls adds work - The windrow falls dawn very fast - The windrow needs intensive mixing - Water absorption of the fresh material is not good - The turning machine blocked by strings during combining Sewage sludge: straw = 1: 3 – 3,5

24. The sewage sludge composting with the straw

25. The peat - C/N = 45-50 - C/N = 45-50 +dry material ~ 75% + mature compost looks like a soil - Bad aeration of the pile - Acidic pH - t 0 can`t rise over 40 0 C - The melting of frozen pile takes long time - The destruction time of pathogens is slow - Needs intensive mixing - Good accumulator of toxically compounds The peat accumulates lot of water Sewage sludge:peat = 1:1,5-2,0

26. Park waste Sewage sludge : park waste = 1:1,5 + quite stable structure + cheap + mature compost like a soil - C/N = 40-60 - t 0 is rising slowly - Needs intensive mixing - Foreign matters, hazardous waste The park waste from autumn and spring are different Syringes!!!

27. Cardboard chips Sewage sludge :cardboard chips = 1:3 + dry mat. 70-75% + free of charge + C/N = 300-400 + shredded material is airy - - Shredding is problematical - The big amount of bulk material may cause the temperature drop under critical level -The content of PAH is higher - Outlook and using of mature compost is problematical

28. Municipal waste C/N = 30-40 Structure problems Non-biodegradable material Biodegradable organic material falls dawn during composting Sewage sludge: municipal waste = 1:1

29. Test piles in 2006  bark  building waste  park waste cardboard waste  municipal waste municipal waste 

30. Temperature inside the windrows t 0 is measured in the depht of 50 cm of the windrows

31. Fertilization quality of mature compost Fertilization quality the same as in case of manure Fertilization quality the same as in case of manure The chemical and biological control more effective as in case of manure The chemical and biological control more effective as in case of manure The manure is more dangerous by biological parameters, because the t 0 is not high enough in anaerobic process to kill pathogens The manure is more dangerous by biological parameters, because the t 0 is not high enough in anaerobic process to kill pathogens The compost have to be mature The compost have to be mature In case of non mature compost the degradation process will continue in soil, the nitrogen may taken off from the soil and the plants may die In case of non mature compost the degradation process will continue in soil, the nitrogen may taken off from the soil and the plants may die

32. Sewage sludge composting Take the bulk material, which is right by structure and by quality Take the bulk material, which is right by structure and by quality You have to mix and pile the raw compost rapidly You have to mix and pile the raw compost rapidly Aerate (mix) the piles after optimum time Aerate (mix) the piles after optimum time Follow the required parameters Follow the required parameters Correct the compost materials content if you need Correct the compost materials content if you need

33. Not enough O 2 Wrong bulkmaterial Not enough H 2 O Not enough N Cold weather Mix the pile Take the right bulkmaterial Add water and mix Add sludge Wait for spring Problems Nothing is happening. Pile dosen`t seem to be heating up at all Temperature is rising slowly and not high Not enough O 2 wrong C/N ratio Not enough H 2 O too much H 2 O mix the pile, change the structure C/N = 20-30 add water and mix add dry bulkmaterial and mix Damp and warm only in the middle of the pile Too small or too large pile Not homogenous compost Cold weather Make the pile in a right size Mix the pile Wait for spring Possible causesSolution

34. Thick bulkmaterial The pile is too wet Less mixing Mix the pile, wait the piles top dries and mix again Add dry materials like straw or leaves Problems The compost in the lump Bad odour not enough not enough O 2 owe moisture the pile is too compact C/N ratio too high The same as previous Add bulk material Possible causessolution Attracts insects, millipedes, slugs etc. This is normal composting Not a problem

35. Thank You! Jüri Haller head of laboratory Tartu Veevärk Ltd ESTONIA jyri.haller@tartuvesi.ee jyri.haller@tartuvesi.ee +372 7306233