Contents Some examples Basic selection considerations Choices between technologies WAWTTAR selection software

Size: px

Start display at page:

Download "Contents Some examples Basic selection considerations Choices between technologies WAWTTAR selection software"

Tamsin Crystal Anderson
5 years ago
Views:

1 Technology selection for sanitation and wastewater treatment Peter van der Steen

2 Contents Some examples Basic selection considerations Choices between technologies WAWTTAR selection software

3 Activated sludge systems Mechanised system Energy intensive Small area Good BOD, TSS and nutrient t removal

4 General process layout Primary sedimentation Secondary sedimentation Influent Aeration tank Effluent Primary sludge Sludge recycle Secondary sludge

13 Trickling filter Attached growth biological treatment

14 Trickling filter Influent Effluent Primary sedimentation Trickling filter Secondary sedimentation

16 Rotating Biological Contactors Attached growth Biofilm formation

17 Cross section Rotating Biological Contactors 1-2 rpm Biodisc/plastic media Shaft Holding tank Water-phase

18 Rotating Biological Contactors

19 COD balance for aerobic and anaerobic system Electricity required for aeration Energy production via biogas

20 A UASB reactor for the treatment of 6000 PE domestic wastewater

21 Influent flow splitter. Each compartment feeds one inlet pipe.

22 How do pond systems look like? Ponds d are simple man-made made basins/lagoons, often surrounded by an earthen embankment. The waste is confined and bacteria stabilise the waste.

23 Advantages of WSPs Very effective removal of pathogens, and therefore effluent suitable for reuse Effective BOD removal Simple and cheap construction, operation and maintenance Low energy requirements Simple sludge management

24 Disadvantages of WSPs Large land area required Performance strongly affected by temperature Potential odour release Low degree of operational control

25 Problem 2/3 rd of all wastewater not treated Many wwtp s not tin operation; or poorly operated Causes: Inappropriate treatment levels Inappropriate treatment technologies a distinctive preference for equipmentintensive solutions, usually involving imported hardware, as opposed to low (soft) technology alternatives.. (Marino and Boland, 1999) Lack of careful integrated planning

26 Integrated Urban Water Management Policy Strategy Masterplan Feasibility study goals/principles approach (for instance IUWM) planning for entire city actions in a sub-sector sector (a pipeline, a WWTP) Design Construction Operation, Monitoring & Evaluation

27 Feasibility study Assumptions, selection of alternatives, effluent standards. Preliminary design of infrastructure Preliminary cost calculations (investment and recurrent: NPV) Cost-benefit analysis Risk analysis Multi criteria analysis

28 Feasibility Determinants to define the feasibility of a technology Site conditions Environmental feasibility Institutional i aspects Community involvement Socio-cultural cultural aspects Economic and financial aspects Technological factors (treatment efficiency)

29 Site conditions Physical environment Urbanisation pattern Existing service level climate topography, soil stability percolation capacity hydrogeology/flooding population lti densities degree of urban planning service levels for water supply service levels for solid waste

30 Options analysis - criteria Social Health Technological Economic Financial Institutional distribution costs/benefits, gender, motivation, local involvement mortality rates, diseases appropriateness, use local resources, market suitability economic return, cost effectiveness costs, sustainability, foreign exchange needs capacity, capability, technical assistant inputs Environmental impacts, environmental costs vs. benefits

31 Options analysis - criteria Very important to realize: Different Stakeholders will use a different set of criteria to judge an alternative.

32 Options analysis - scores Estimate scores for the selected criteria for the alternative options: High-low. +/-. Extensive/limited. Scale 1-5.

33 Multicriteria analysis Criteria Weight Investment t cost Important t Yearly cost Robusteness ess Institutional organisation Cost-recovery Extremely important Important t Very important Very important

34 Multicriteria analysis Criteria Weight Score Investment cost Yearly cost Robusteness Institutional organisation Cost-recovery Total score

35 Choices between technologies

36 Technology selection 1. Wet or Dry 2. On-site or Off-site 3. Sewer type 4. Discharge/reuse criteria 5. Treatment technology Physico-chemical h i or Biological i l Aerobic or Anaerobic Mechanised or Natural

37 Site conditions Increase in population density Increase in water supply dry systems service level On-site sanitation On-site sanitation ti systems (pit latrines) Off-site sanitation wet systems

38 Site conditions Increase in population density Increase in water supply dry systems service level On-site sanitation Off-site sanitation Nightsoil collection systems wet systems

39 Site conditions Increase in population density Increase in water supply dry systems service level On-site sanitation Off-site sanitation wet systems On-site sanitation with leaching facilities

40 Site conditions Increase in population density Increase in water supply dry systems service level On-site sanitation Off-site sanitation On-site sanitation ti Nightsoil systems collection (pit latrines) systems wet systems On-site sanitation with leaching facilities Off-site transportation and treatment of sewage

41 Site conditions Increase in population density Increase in water supply dry systems service level On-site sanitation Off-site sanitation On-site sanitation ti Nightsoil systems collection (pit latrines) systems wet systems On-site sanitation with leaching facilities On-site sanitation (individual or shared) with off-site disposal Off-site transportation and treatment of sewage

42 Sewerage Conventional sewerage Shallow (condominial) sewerage Settled sewerage

43 Sewerage Shallow (condominial) sewerage

44 Sewerage cost

45 Settled sewerage

47 Sewer costs and On-site/off-site selection flow diagram

48 Technology selection 1. Wet or Dry 2. On-site or Off-site 3. Sewer type 4. Discharge/reuse criteria 5. Treatment technology Physico-chemical or Biological Aerobic or Anaerobic Mechanised or Natural

51 Technology selection 1. Wet or Dry 2. On-site or Off-site 3. Sewer type 4. Discharge/reuse criteria 5. Treatment technology Physico-chemical or Biological Aerobic or Anaerobic Mechanised or Natural

52 Selection flow charts

53 Selection flow charts

55 Aerobic versus Anaerobic

56 Comparison Aerobic - Anaerobic

57 Example: Cost savings Brewery (2,000,000 hl beer/y)

87% cost reduction sludge disposal Biogas used for steam

58 Effects on operating costs: 90-95% 95% COD,BOD removal 80% lower power consumption 100% lower N/P consumption 87% cost reduction sludge disposal Biogas used for steam prod. Total savings: $ 600,000/y (investment recovered in2years)

59 Aerobic versus Anaerobic

60 Nutrient recovery THE NITROGEN CYCLE OUT OF BALANCE

61 Nitrogen reuse NH 4 Crops Protein Fish Duckweed Crops Fertiliser N 2 Nitrification Denitrification

62 NH 4 to N 2

63 NH4 to fish

64 NH4 to crops

65 Check list selection process technology (Metcalf and Eddy) 1. Process applicability 11.Environmental constraints 2. Applicable flow rate 3. Applicable flow variation 4. Influent wastewater characteristics 5. Inhibiting and unaffected constituents 6. Climatic constraints 7. Reactor kinetics and reactor selection 8. Performance 9. Treatment residuals 12.Chemical requirements 13.Energy requirements 14.Other resource requirements 15.Personnel requirements 16.Operating + maintenance requirem 17.Ancillary processes 18.Reliability 19.Complexity 10.Sludge processing 20.Compatibility 21.Land availability

66 Costs versus level of treatment rational c osts Investme ent & ope (USD/m 3 ) 4,5 4,0 3,5 3,0 25 2,5 2,0 1,5 1,0 0,5 00 0,0 Primary treatment Secondary treatment Tertiary treatment Removal efficiency (%) Advanced treatment Primary Secondary Tertiary Advanced BOD >99 >99 COD >90 >90 TSS >95 >99 P tot >90 >95 N tot >95 >95 Source: Adopted from IHE Lecture notes, Wastewater Engineering 1, Veenstra, 2001

67 Technology selection Discounted costs for 100,000 p.e. WWTP's over 20 yrs at 10% Costs in mln ETB Waste Stabilization Ponds Carrousel Trickling filter all costs runnig costs only investment cost only

68 A Decision Support Model for Prefeasibility Analysis of WATER AND WASTEWATER TREATMENT TECHNOLOGIES OG APPROPRIATE FOR REUSE Humboldt State University USA

69 x x x

Best Practice in Sewage and Effluent Treatment Technologies

Best Practice in Sewage and Effluent Treatment Technologies Contents 1 Wastewater - Introduction 1 1.1 Earth s ecological system 1 1.1.1 Water effect on ecology 2 1.1.2 Wastewater generation 3 1.2 Wastewater