Presenter: Michael Short * Nancy Cromar

Transcription

1 Importance of hydraulic characterisations in waste stabilisation pond research: results from pilot-scale algal, duckweed, rock filter and attached-growth media reactors Presenter: Michael Short * Co-authors: Howard Fallowfield Nancy Cromar Department of Environmental Health, Flinders University, Adelaide, South Australia *UNSW Water Research Centre, University of New South Wales, Sydney, Australia

2 We all know and love WSPs Waste Stabilisation Ponds (WSPs) Open-air, flow-through, shallow earthen basins for wastewater treatment Advantages and limitations are well known All shapes and sizes; can cover a large area BACKGROUND

3 The local WSPs Waste Stabilisation Ponds (WSPs) Open-air, flow-through, shallow earthen basins for wastewater treatment Advantages and limitations are well known All shapes and sizes; can cover a large area The Bolivar WSP system (north of Adelaide) comprises 350 ha of shallow ( 1.3 m) facultative / maturation ponds with an hydraulic throughput of around 145 ML d 1 largest WSP system operating in Southern Hemisphere BACKGROUND

4 The Bolivar WSP network WSPs DAF/F plant Activated Sludge Plant Reuse BACKGROUND Primary sedimentation Image courtesy of United Water International and David Sweeney

5 The problem with WSPs Major limitation is often high concentration of algal solids / biomass in final pond effluents Issue has long been established as one of the most serious performance problems associated with WSPs BACKGROUND

6 The problem with WSPs Major limitation is often high concentration of algal solids / biomass in final pond effluents Issue has long been established as one of the most serious performance problems associated with WSPs ongoing algal issues experienced at Bolivar (DAF/F) BACKGROUND DAF/F plant Photographs: David Sweeney

7 Bolivar DAF/F concerns DAF/F plant treats WSP effluent for horticultural reuse DAF/F operators identified high algal solids as a significant threat to treatment process BACKGROUND

8 Bolivar DAF/F concerns DAF/F plant treats WSP effluent for horticultural reuse DAF/F operators identified high algal solids as a significant threat to treatment process BACKGROUND

9 Bolivar DAF/F concerns Compromised DAF/F performance: Undesirable turbidity breakthrough DAF/F plant treats WSP effluent for horticultural reuse DAF/F operators identified high algal solids as a significant threat to treatment process BACKGROUND

10 Bolivar DAF/F concerns Compromised DAF/F performance: Undesirable turbidity breakthrough Premature filter-bed clogging DAF/F plant treats WSP effluent for horticultural reuse DAF/F operators identified high algal solids as a significant threat to treatment process BACKGROUND

11 Bolivar DAF/F concerns DAF/F plant treats WSP effluent for horticultural reuse DAF/F operators identified high algal solids as a significant threat to treatment process Compromised DAF/F performance: Undesirable turbidity breakthrough Premature filter-bed clogging Excessive chemical polymer and flocculant dosing ( $ ) BACKGROUND

12 Bolivar DAF/F concerns DAF/F plant treats WSP effluent for horticultural reuse DAF/F operators identified high algal solids as a significant threat to treatment process Compromised DAF/F performance: Undesirable turbidity breakthrough Premature filter-bed clogging Excessive chemical polymer and flocculant dosing ( $ ) BACKGROUND In-pond WSP upgrades proposed as possible solution to reduce load on DAF/F plant (increase process efficiency)

13 In-pond WSP effluent upgrades Three candidate upgrades identified: UPGRADES

14 In-pond WSP effluent upgrades Three candidate upgrades identified: 1. Duckweed UPGRADES

15 In-pond WSP effluent upgrades Three candidate upgrades identified: 1. Duckweed 2. Rock filters UPGRADES

16 In-pond WSP effluent upgrades Three candidate upgrades identified: 1. Duckweed 2. Rock filters 3. Attached-growth media UPGRADES

17 1. Duckweed (DW) In-pond WSP effluent upgrades Duckweed: Small floating plant; dense surface cover; low-tech; proven potential for WSP upgrading (SS, BOD 5, algae, nutrients...) UPGRADES

18 2. Rock filter (RF) In-pond WSP effluent upgrades Rock filters: Random water flow through rock bed; enhanced surface area; physical + biological treatment; low-tech; potential for WSP upgrading (SS, BOD 5, algae, nutrients?) UPGRADES

19 In-pond WSP effluent upgrades 3. Horizontal-flow attached-growth media (HF-AGM) Horizontal-flow attached-growth media : Forced lateral flow; high voids & surface area media; novel use (used in vertical-flow TFs); physical + biological treatment; potential for WSP upgrading (SS, BOD 5, algae(?), nutrients) UPGRADES 19 mm ø TKP-319 media available from 2H Plastics Australia (

20 In-pond WSP effluent upgrades Duckweed and rock filters both relatively popular in-pond WSP upgrade technologies UPGRADES

21 In-pond WSP effluent upgrades Duckweed and rock filters both relatively popular in-pond WSP upgrade technologies AGM systems not so well researched, but have shown promise as pond upgrade UPGRADES

22 In-pond WSP effluent upgrades Duckweed and rock filters both relatively popular in-pond WSP upgrade technologies AGM systems not so well researched, but has shown promise as pond upgrade no prior direct comparisons of these 3 techniques UPGRADES

23 In-pond WSP effluent upgrades DW and RFs both relatively popular in-pond WSP upgrade technologies AGM systems not so well researched, but has shown considerable promise no prior direct comparisons of these 3 techniques This research presents first direct performance comparison of DW, RF and AGM systems for WSP effluent polishing & first assessment of novel HF-AGM in a WSP application RATIONALE

24 In-pond WSP effluent upgrades DW and RFs both relatively popular in-pond WSP upgrade technologies AGM systems not so well researched, but has shown considerable promise no prior direct comparisons of these 3 techniques This research presents first direct performance comparison of DW, RF and AGM systems for WSP effluent polishing & first assessment of novel HF-AGM in a WSP application RATIONALE HOW..?

25 Research pilot plant Pilot plant built to assess the three methods for WSP effluent upgrading; duckweed cover (DW), rock filters (RFs) + METHODS

26 Research pilot plant and horizontal-flow attached-growth media (HF-AGM) METHODS Open pond (OP)

27 Research pilot plant and horizontal-flow attached-growth media (HF-AGM) METHODS all assessed against a parallel Open Pond control (algalbased pond) Open Pond (OP)

28 Pilot plant operation m 3 pond reactors operated in 3 parallel series (1 m depth) Wastewater inflow from header tank (HT) into reactor series METHODS Short et al. (2007) Water Science and Technology 55(11):

29 Pilot plant operation Perforated 25 mm ø PVC inlet/outlet manifolds as opposed to single duct hydraulic inlet and outlets METHODS

30 Pilot plant operation Inlet /outlet mixing chambers for inflow distribution (RF/AGM) METHODS

31 Pilot plant operation & monitoring m 3 reactors operated in 3 parallel series (1 m depth) METHODS

32 Pilot plant operation & monitoring m 3 reactors operated in 3 parallel series (1 m depth) Duckweed (native Lemna disperma); 2 cm surface mat METHODS

33 Pilot plant operation & monitoring m 3 reactors operated in 3 parallel series (1 m depth) Duckweed (native Lemna disperma); 2 cm surface mat Rock filters; 10 cm ø rock media ( 55% voids; 40 m 2 m 3 ) METHODS

34 Pilot plant operation & monitoring m 3 reactors operated in 3 parallel series (1 m depth) Duckweed (native Lemna disperma); 2 cm surface mat Rock filters; 10 cm ø rock media ( 55% voids; 40 m 2 m 3 ) Attached-growth media; 19 mm (95% voids; 150 m 2 m 3 ) METHODS

35 Pilot plant operation & monitoring m 3 reactors operated in 3 parallel series (1 m depth) Duckweed (native Lemna disperma); 2 cm surface mat Rock filters; 10 cm ø rock media ( 55% voids; 40 m 2 m 3 ) Attached-growth media; 19 mm (95% voids; 150 m 2 m 3 ) Open pond; control for effects of quiescent impoundment METHODS

36 Pilot plant operation & monitoring m 3 reactors operated in 3 parallel series (1 m depth) Duckweed (native Lemna disperma); 2 cm surface mat Rock filters; 10 cm ø rock media ( 55% voids; 40 m 2 m 3 ) Attached-growth media; 19 mm (95% voids; 150 m 2 m 3 ) Open pond; control for effects of quiescent impoundment WSP effluent (2 mm screened) loaded at m 3 m 3 d 1 METHODS

37 Pilot plant operation & monitoring m 3 reactors operated in 3 parallel series (1 m depth) Duckweed (native Lemna disperma); 2 cm surface mat Rock filters; 10 cm ø rock media ( 55% voids; 40 m 2 m 3 ) Attached-growth media; 19 mm (95% voids; 150 m 2 m 3 ) Open pond; control for effects of quiescent impoundment WSP effluent (2 mm screened) loaded at m 3 m 3 d 1 Sampled at least once per week during 12 month operation METHODS

38 Pilot plant operation & monitoring m 3 reactors operated in 3 parallel series (1 m depth) Duckweed (native Lemna disperma); 2 cm surface mat Rock filters; 10 cm ø rock media ( 55% voids; 40 m 2 m 3 ) Attached-growth media; 19 mm (95% voids; 150 m 2 m 3 ) Open pond; control for effects of quiescent impoundment WSP effluent (2 mm screened) loaded at m 3 m 3 d 1 Sampled weekly during 12 month operation Physicochemistry (DO, ph, ORP, temp); BOD 5 ; TOC; SS/VSS; NH 4+ -N; NO 3 -N; PO 4 3 -P; microbial indicators (FC/E. coli); chlorophyll a (algal biomass); algal and zooplankton populations (number/biomass and speciation) METHODS

39 Pilot plant operation & monitoring m 3 reactors operated in 3 parallel series (1 m depth) Duckweed (native Lemna disperma); 2 cm surface mat Rock filters; 10 cm ø rock media ( 55% voids; 40 m 2 m 3 ) Attached-growth media; 19 mm (95% voids; 150 m 2 m 3 ) Open pond; control for effects of quiescent impoundment WSP effluent (2 mm screened) loaded at m 3 m 3 d 1 Sampled weekly during 12 month operation Physicochemistry (DO, ph, ORP, temp); BOD 5 ; TOC; SS/VSS; NH 4+ -N; NO 3 -N; PO 3 4 -P; microbial indicators (FC/E. coli); chlorophyll a (algal biomass); algal and zooplankton populations (number/biomass and speciation) METHODS Watch this space

40 Hydraulic characterisations Hydraulic tracers run at HLRs m 3 m 3 d 1 (high-end of WSP HLRs) low strength Bolivar effluent ( BOD 5 of 4 8 mg L 1 ) Reactor flow hydraulics characterised post hoc no flow pre-validation Rhodamine WT + SCUFA fluorometer/data logger Impulse stimulation slug injection method Fast, simple, accurate (SCUFA detection limit 0.04 ppb) only used 300 μl of rhodamine stock per run! METHODS

41 Ideal reactor hydraulics 1. Plug flow ( piston flow ) TUTORIAL

42 Ideal reactor hydraulics 1. Plug flow ( piston flow ) RTD curve TUTORIAL

43 Ideal reactor hydraulics 1. Plug flow ( piston flow ) 2. Completely mixed flow RTD curve TUTORIAL

44 Ideal reactor hydraulics 1. Plug flow ( piston flow ) 2. Completely mixed flow RTD curve RTD curve TUTORIAL

45 Pilot plant reactor hydraulics What was the flow pattern in our pilot reactors..? RESULTS

46 Pilot plant reactor hydraulics Tracer studies revealed more mixed than plug flow reflects common WSP hydraulics in situ Duckweed reactors Open pond reactors RESULTS Normalized RTD curve Normalized RTD curve

47 Pilot plant reactor hydraulics Tracer studies revealed more mixed than plug flow reflects common WSP hydraulics in situ Rock filters HF-AGM reactors RESULTS Normalized RTD curve Normalized RTD curve

48 Pilot plant reactor hydraulics RESULTS

49 Pilot plant reactor hydraulics No evidence of improved flow under duckweed cover scale issues (wind effects)? RF experienced least ideal flow hydraulics problem reported elsewhere Novel HF-AGM achieved lowest dead volume more useable volume (better wastewater treatment?) RESULTS

50 Final summary WSP upgrade hydraulics: Good reproducibility between tracer experiments Rock filters displayed the most compromised flow hydraulics (consistent with other research) Flow patterns in pilot-scale DW and OP reactors were sub-optimal (but better than 60% dead spaces recorded by Zimmo, 2003) AGM was the most ideal flow (<9% dead volume!) Post hoc nature of hydraulic assessments not ideal Future work should involve flow pre-validations (optimise manifold design / configuration) SUMMARY

51 Further research WSP upgrades: Assess hydraulic characteristics of DW, RF, HF-AGM at different HLRs (lower, higher) Investigate different HF-AGM channel sizes 12 mm (240 m 2 m 3 ); 27 mm (125 m 2 m 3 ) In-pond trials of these WSP upgrade technologies validate pilot-scale performance data FUTURE WORK

52 Acknowledgements Thanks to: Danny Tintor, John Nixon, David Sweeney (United Water International) Ben van den Akker, Richard Evans, Akio Yamamoto AWA / IWA, UNSW for travel support Committee Chairs: Marcos von Sperling & Andy Shilton IWA WSP specialist group + Brazilian Water Resources Association for hosting this event THANK YOU!

53 References 1. Short, M.D., Nixon, J.B., Cromar, N.J. and Fallowfield, H.J. (2007). Water Science and Technology 55(11): Swanson, G.R. and Williamson, K.J. (1980). Journal of the Environmental Engineering Division, ASCE 106(EE6): Zimmo, O.R. (2003). Nitrogen transformations and removal mechanisms in algal and duckweed waste stabilisation ponds. UNESCO-IHE, Institute for Water Education, Birzeit University, Delft, The Netherlands. PhD Thesis, 133 p. Questions

54

55 Pilot plant operational summary Pilot plant operation split into two monitoring periods over two years from July of 2005 to August of 2006 METHODS

56 Individual reactor characteristics RESULTS

57 Presentation Overview Introduction to the local Bolivar waste stabilisation ponds (WSPs) OUTLINE

58 Presentation Overview Introduction to the local Bolivar waste stabilisation ponds (WSPs) Introduce the operational problem at Bolivar OUTLINE

59 Presentation Overview Introduction to the local Bolivar waste stabilisation ponds (WSPs) Introduce the operational problem at Bolivar Describe the research pilot plant used to investigate various WSP upgrade systems OUTLINE

60 Presentation Overview Introduction to the local Bolivar waste stabilisation ponds (WSPs) Introduce the operational problem at Bolivar Describe the research pilot plant used to investigate various WSP upgrade systems Present findings from hydraulic characterisations OUTLINE

61 Presentation Overview Introduction to the local Bolivar waste stabilisation ponds (WSPs) Introduce the operational problem at Bolivar (rationale) Describe the pilot plant used to investigate selected WSP upgrades Present findings from hydraulic characterisations OUTLINE Summary of relevant information; highlighting potential further research