EXTENSIVE AND NATURAL SYSTEMS FOR WASTEWATER TREATMENT

Transcription

1 10 th Specialized Conference on Small Water and Wastewater Treatment Systems Venice, April 2011 EXTENSIVE AND NATURAL SYSTEMS FOR WASTEWATER TREATMENT Marcos von Sperling Federal University of Minas Gerais Brazil

2 EXTENSIVE AND NATURAL SYSTEMS FOR WASTEWATER TREATMENT Cover only wastewater treatment Reflect more the experience at warm-climate regions, particularly Brazil Express some personal opinions Photos: not only small systems PRESENTATION OUTLINE Stabilization ponds Constructed wetlands UASB reactors + post-treatment

3 FEDERAL UNIVERSITY OF MINAS GERAIS - BRAZIL Centre for Research and Training in Sanitation UFMG - COPASA

4 IWA SPECIALIST GROUPS WITH GREATER INTERFACE WITH EXTENSIVE AND NATURAL SYSTEMS Anaerobic digestion Resources Oriented Sanitation (EcoSan) Sanitation and Water Management in Developing Countries Small Water and Wastewater Systems Use of Macrophytes in Water Pollution Control Waste Stabilisation Ponds

5 WASTE STABILIZATION PONDS

6 IWA Specialist Group on Waste Stabilization Ponds 8 international conferences (next one: Adelaide, Australia, 1-4 August 2011)

7 IWA Specialist Group on Waste Stabilization Ponds Books published by IWA on stabilization ponds

8 STABILIZATION PONDS Facultative Brazil

9 STABILIZATION PONDS Anaerobic pond Facultative pond Brazil

10 STABILIZATION PONDS Aerated lagoon South of France Aerators on during wine production periods

11 STABILIZATION PONDS Anaerobic facultative - maturation ponds Northeast Brazil - 1 Anaer. pond + 1 Facult. pond + 3 Matur. ponds (100 ha)

12 UASB POLISHING PONDS Experimental WWTP UFMG/COPASA inhab

13 REMOVAL OF ORGANIC MATTER FACULTATIVE PONDS

14 FACULTATIVE PONDS Design criteria Surface organic loading rate Depth Hydraulic retention time Geometry (length / breadth ratio)

15 FACULTATIVE PONDS Design criteria Surface organic loading rate - L s Mara: L s = 350 x ( T) (T-25) (T = mean air temperature in coldest month) 400 Surface loading rate as a function of temperature Ls (kgbod/ha.d) Ls T (oc)

16 FACULTATIVE PONDS Effluent BOD Total BOD = Soluble BOD + Particulate BOD

17 FACULTATIVE PONDS Hydraulic models Plug flow Completely mixed S -K.t = S 0 e S = S 0 1+ K.t Cells in series Dispersed flow S = S (1+ K 0 t ) n n S a = = S 0. (1+ a) K.t.d e 4ae a/2d 1/2d (1 a) 2 e a/2d

18 FACULTATIVE PONDS Effluent soluble BOD concentration Completely mixed: Primary ponds: K = 0.30 to 0.40 d -1 Secondary ponds: K = 0.25 to 0.32 d -1

19 FACULTATIVE PONDS Hydraulic models Relationship between reaction coefficients (K)

20 Tracer studies FACULTATIVE PONDS Hydraulic models CFD modelling (long time for field trials) (e.g. studies on the influence of baffles)

21 FACULTATIVE PONDS Effluent particulate BOD concentration No adequate models for predicting effluent BOD and SS 1 mgss/l = 0.3 to 0.4 mgbod 5 /L 1 mgss/l = 1.0 to 2.0 mgcod/l Pond effluents: 60 to 100 mgss/l (for design)

22 FACULTATIVE PONDS Effluent polishing (algae removal) Coarse rock filter: Experiments UFMG: Stones: 3 to 8 cm H = 0.40 m HLR: 0.5 to 1.5 m 3 /m 3.d

23 FACULTATIVE PONDS Effluent polishing (algae removal) Floating macrophytes duckweed (Lemna) Experimental WWTP UFMG/Copasa

24 PRIMARY FACULTATIVE PONDS Sand accumulation Brazil Prior grit removal is recommended

25 FACULTATIVE PONDS Sludge accumulation Colombia

26 FACULTATIVE PONDS Sludge accumulation 0.03 to 0.08 m 3 /inhab.year 2 to 3 cm per year Operation for 20 years without need of sludge removal Complex operation when removal is necessary

27 REMOVAL OF PATHOGENIC ORGANISMS IN PONDS

28 REMOVAL OF PATHOGENIC ORGANISMS Removal of bacteria and viruses Die-off mechanisms (high UV radiation, high ph, high DO,...) Substantial research in the past years (source: Nelson, 2009)

29 REMOVAL OF PATHOGENIC ORGANISMS Removal of bacteria and viruses Molecular biology methods (PCR, FISH, Quantitative PCR) Detection of actual pathogenic organisms, not only indicators RS P1RS P1RS RS a b c PCR products from amplification of DNA from: a) Escherichia coli, b) Salmonella enterica subsp. enterica, c) Enterococcus spp., d) Shigella dysenteriae. Legend: RS (raw sewage), UASB (UASB effluent), P1 (polishing pond 1 effluent) (source: Godinho et al 2009)

30 FACULTATIVE AND MATURATION PONDS Coliform removal efficiency (log units) 186 ponds around the world LOG UNITS REMOVED IN EACH POND OF THE SERIES 3,5 3,0 LOG UNITS REMOVED 2,5 2,0 1,5 1,0 0,5 0,0 PRIM SEC MAT1 MAT2 MAT345 CATEGORY Median 25%-75% 5%-95%

31 MATURATION PONDS Baffled ponds Samambaia, Brazil (180,000 inhab)

32 MATURATION PONDS Ponds in series 1e10 EFFLUENT E. COLI CONCENTRATIONS PHASE 1 1e9 1e8 E. coli (MPN/100ml) 1e7 1e6 1e RAW UASB POND1 POND2 POND3 POND4 Max Min 75% 25% Median Experimental WWTP UFMG/Copasa (250 inhabitants) Depth of ponds: H: 0.4 to 0.8 m (shallow ponds)

33 FACULTATIVE AND MATURATION PONDS Coliform die-off coefficient (K b ) - dispersed flow 186 ponds around the world 6,0 Kb disp (20o C) vs depth H 5,0 4,0 Kb (1/d) 3,0 2,0 1,E+10 1,E+08 Effluent coli estimated x observed 1,0 Estim 1,E+06 1,E+04 0,0 0,00 1,00 2,00 3,00 H (m) 1,E+02 1,E+00 1,E+00 1,E+02 1,E+04 1,E+06 1,E+08 1,E+10 Obs

34 FACULTATIVE AND MATURATION PONDS A A H V 2H V For the same surface area A: Increase H increase V increase HRT But K b decreases Efficiency does not increase

35 REMOVAL OF PATHOGENIC ORGANISMS Removal of protozoan cysts and helminth eggs Mechanism: sedimentation

36 FACULTATIVE AND MATURATION PONDS Helminth eggs removal Ayres et al model (2002) Mean removal efficiency: E = 100.[1 0,14.e ( 0,38.t) ] REMOVAL EFFICIENCY OF HELMINTH EGGS 6,0 Log units removed 5,0 4,0 3,0 2,0 1,0 Average values 95% confidence level WHO (irrigation): < 1 egg/l 0, Hydraulic detention time(d)

37 FACULTATIVE AND MATURATION PONDS Helminth eggs removal Ayres et al model (2002) 100 HELMINTH EGGS - FIRST POND ESTIMATED (AYRES) AND OBSERVED EFFICIENCY EFFICIENCY (% OBS ESTIM RETENTION TIME (d) Average values from five different ponds in Brazil

38 FACULTATIVE AND MATURATION PONDS Helminth eggs removal Baffled maturation pond in Brazil (4 baffles) Helminth eggs in the sludge after two years

39 STABILIZATION PONDS Avoid population access!

40 NITROGEN REMOVAL

41 FACULTATIVE AND MATURATION PONDS Nitrogen removal 80 NITROGEN REMOVAL EFFICIENCY Efficiency (%) ph=9,0 ph=8,5 ph=8,0 ph=7,5 ph=7, HDT (d) T= 20oC Values from one of the equations available in the literature Assumption that NH 3 volatilization is the prevailing mechanism Considerable debate over the mechanisms Removal efficiencies are not high

42 Volatilization does not seem to be a major mechanism FACULTATIVE AND MATURATION PONDS Nitrogen removal Experimental WWTP UFMG, Brazil Experimental WWTP UK (Miller et al, 2009) Capture of ammonia escaped through the surface of a pond, in order to measure volatilization rate Studies with marked nitrogen isotopes ( 15 N)

43 MATURATION PONDS Nitrogen removal NITROGEN FRACTIONS Experimental WWTP UFMG-Copasa N fraction removed: ammonia Poor nitrification

44 MATURATION PONDS x WETLANDS Ammonia removal Experiments from Univ. São Paulo, Brazil (two ponds in parallel): H 0.5m 1.0m For the same surface area A: Greater H Higher V Higher HRT Lower ammonia removal efficiency Pond with H=0.5m (L/B = 16)

45 PONDS: FUTURE CHALLENGES

46 PONDS: FUTURE CHALLENGES Reduction of required area Better understanding of the removal mechanisms (e.g. pathogen decay; nitrogen removal) Implementation of rational models design optimization (but not much scope for operational control) Carbon sequestration and energy production (biodiesel, hydrogen production from cyanobacteria...)...

47 CONSTRUCTED WETLANDS

48 IWA Specialist Group on Use of Macrophytes in Water Pollution Control 12 international conferences Next conference: Perth, Australia

49 IWA Specialist Group Use of Macrophytes in Water Pollution Control Books published by IWA on constructed wetlands Constructed Wetlands for Pollution Control Processes, Performance, Design and Operation Author(s): R. Kadlec, R. Knight, J. Vymazal, H. Brix, P. Cooper, R. Haberl Publication Date: 2000

50 Surface flow constructed wetlands New Zealand (pond effluent polishing)

51 Horizontal subsurface-flow constructed wetlands Planted (Typha) Unplanted Experimental WWTP UFMG / COPASA (50 inhab each unit) Surface hydraulic loading: 0.1 m 3 /m 2.d Hydraulic retention time (V.porosity/Q): 1.2 d

52 Horizontal subsurface-flow constructed wetlands Measured filtered COD concentrations along the length Planted wetland Unplanted wetland COD concentration (mg/l) % 25% 50% 75% 100% Relative distance 25% 50% 90% 10% Min Max 75% COD concentration (mg/l) % 25% 50% 75% 100% Relative distance 25% 50% 90% 10% Min Max 75% Water losses (evapotranspiration): increase in effluent concentrations Compute removal efficiencies in terms of loads (and not concentrations) Actual role of plants? (debate in the literature) Capacity for N and P removal?

53 Horizontal subsurface-flow constructed wetlands Clogging surface flow Experimental WWTP UFMG-Copasa Source: Knowles et al (2010) Modelling of clogging development and hydraulic conductivity reduction Refurbishment / cleaning of the beds

54 Vertical flow constructed wetlands French (CEMAGREF) system Tifton Experimental WWTP UFMG / COPASA (100 inhab)

55 Vertical flow constructed wetlands Hydraulic behaviour Q (Litros/minuto) Teste 5 (FV-NP) Teste 11 (FVP-2) Tempo (horas) Outflow as a function of time E (t) 0,0045 0,0040 0,0035 0,0030 0,0025 0,0020 0,0015 0,0010 0,0005 0,0000 Initial tests (clean filter) After a 11 months operation (used filter) Time(min) Tracer studies - DTD curve Experimental WWTP UFMG / COPASA (100 inhab)

56 Vertical flow constructed wetlands Potential for nitrification 30 Nitrogen fractions (mg/l) N nitrate N ammonia N organic Raw Unplanted Planted Experimental WWTP UFMG / COPASA (100 inhab)

57 UASB REACTORS AND POST- TREATMENT OF ANAEROBIC EFFLUENTS

58 SMALL UASB REACTORS Experimental WWTP UFMG / COPASA (250 inhab)

59 UASB REACTOR From small to large installations Experimental WWTP UFMG / COPASA Onça WWTP COPASA (Brazil) Hundreds of inhabitants One million inhabitants

60 UASB + POST-TREATMENT Any of the technologies for treating raw sewage can be used as post treatment with advantages (in warm climate regions) Advantages: Certain reduction in construction costs lower volume/area of the units Large reduction in operating costs less energy consumption less quantity of sludge to be produced

61 UASB + POST-TREATMENT Polishing ponds UASB Reator UASB Lagoa de polimento Pond WWTP UFMG Copasa (250 inhab)

62 UASB + POST-TREATMENT Overland flow Overland flow Itabira, Brazil (300 inhab) Loading rate: 0.2 to 0.5 m 3 /h per meter width Length: 30 to 45 m Slope: 2 to 8%

63 UASB + POST-TREATMENT Horizontal subsurface-flow constructed wetlands Planted Unplanted Experimental WWTP UFMG / COPASA (50 inhab each unit)

64 UASB + POST-TREATMENT Activated sludge Rio Claro, Brazil - 100,000 inhab

65 UASB + POST-TREATMENT Trickling filter Itabira, Brazil - 70,000 inhab

66 UASB + POST-TREATMENT Trickling filter Experimental WWTP UFMG / COPASA (500 inhab)

67 UASB + POST-TREATMENT Trickling filter Experimental WWTP UFMG / COPASA (UASB: inhab; TF: 300 inhab)

68 CONCLUDING REMARKS There is no overall best treatment process In each particular case, select the system with the best performance from the technical and economical studies

69 THANK YOU VERY MUCH! ENJOY THE CONFERENCE!