Opportunities for Sectoral Synergy in Public Sector Waste Management UNDP Waste Management Experts Meeting Havana, Cuba, October 27 - 31, 2003

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Opportunities for Sectoral Synergy in Public
Sector Waste Management UNDP Waste Management
Experts MeetingHavana, Cuba, October 27 - 31,
2003

• Authors
• Hugh Sealy, Ph.D., P.Eng.
• Kev L. Metcalfe, P.Eng.
• Norm J. Nuttall, P.Eng.
• Stantec Consulting International Ltd.

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Introduction

• In many Caribbean countries, there exists the
  potential for cooperation between the agencies
  responsible for solid waste and domestic
  wastewater (sewage) management, which would
  result in improved operations, increased
  environmental and economic benefits and reduced
  risks.

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Cooperative Approach
Economic Benefits
EnvironmentalBenefits
Risk ManagementBenefits
Result Improved Operation and Reduced Costs
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Constraints to Cooperation

• Unfortunately, this potential synergy tends to be
  unrealized, perhaps for the following reasons
• Responsibility for solid waste management and
  wastewater management usually resides within
  separate departments/ministries.
• The concept of an integrated approach to both
  waste management (solid, liquid and gas),
  including residuals management is not yet
  pervasive within the region.
• Funding tends to be project specific and linear
  in programming and does not allow for
  inter-agency cooperation.

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Constraints to Cooperation

• Traditionally, low tech approaches have been used
  for SWM in the Caribbean, whereas it may be
  argued that WASAs have been exposed to more
  complex technologies in the treatment and
  delivery of potable water and the treatment and
  disposal of wastewater. For example, the
  Barbados Water Authority (BWA) recently specified
  a mechanical treatment plant for septage and
  sludge treatment rather than low tech lagoons.

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Technology Evolution

• Dumps
• Simple Lagoons

Engineered Sanitary Landfills Complex Mechanical
Treatment Plants
Higher Level of Environmental Protection
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Objective

• The objective of the following paper is to
  present examples from the Caribbean (in
  particular using case studies from the Bahamas
  and from Barbados) where it can be shown that
  cooperation between solid waste and wastewater
  utilities in residuals management may result in
  benefits to both utilities.

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Waste Streams Residuals
A List
B List
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Residuals (Liquids, Gases Bio-solids)

• Leachate from landfills that have a collection
  system
• Landfill gas generated from the decomposition of
  wastes
• Septage from septic treatment systems
• Screenings from primary sewage and septage
  facilities
• Sludge (primary secondary) from sewage
  treatment plants

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Other Residuals

• Grease from food preparation
• Used motor oil
• Sludges from car washes
• Blood and by-products from abattoirs
• Manure
• Petroleum contaminated soils

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Disposal Options for Residuals

• Leachate
• Anaerobic / Aerobic lagoons with mechanical
  aeration
• Effective treatment
• Recycle leachate by re-circulating it through the
  landfill
• Increased waste decomposition of solid waste in
  landfill
• Reduced strength of leachate

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Disposal Options for Residuals

• Landfill Gas
• Collected and flared or used to produce energy
• Passive venting
• Re-circulation of leachate can affect rate of gas
  generation
• Approximately 40 to 80 tonne per day landfill
  site could generate 1 MW of energy

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Disposal Options for Residuals

• Septage
• Series of lagoons settling pond, anaerobic and
  aerobic
• Incorporated into Primary Sludge disposal

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Disposal Options for Residuals

• Sewage Sludge
• Primary Treatment Sludge
• Direct disposal to dedicated cells on site
• Primary digestors at treatment plant
• Secondary Treatment Sludge
• Co-composting
• Landfarming
• Lagoons

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Disposal Options for Residuals

• Screenings
• Dedicated cells
• Landfilled
• Co-composting

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Synergistic Residuals Management Options

• The following two technologies may provide
  opportunities for co-disposal of residuals in the
  Caribbean
• Bioreactor Landfill
• Co-composting

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Bioreactor Landfill

• Designed to rapidly change and biodegrade organic
  component of solid waste stream
• Adding sufficient liquids and air
• Aerobic, Hybrid and Anaerobic

Waste Age, Phil OLeary Patrick Walsh, June
2002, p.64
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Bioreactor Landfill

• Most Easily Adapted to Caribbean Anaerobic.
• Moisture content most important aspect. Upwards
  of 65 required. Recirculating leachate alone
  (at least in the initial stages of the landfill
  life) may not achieve the desired moisture
  content.
• Leachate, storm-water, screenings, sewage sludge,
  septage and other waste treatment effluents can
  be added to achieve the desired moisture content.
• Benefits Accelerated decomposition, reduced
  leachate treatment and disposal costs, reduced
  need for leachate treatment facilities, reduced
  post closure costs and increased landfill gas
  generation.

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Leachate Generation
Estimated Leachate Generation Quantities New
Providence
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Co-composting

• Defined as composting of organic waste
  supplemented with a range of materials (e.g.
  septage, sludge, abattoir wastes).
• Carbon to Nitrogen Ratio (CN) is key. The ideal
  CN ratio is 25-301. The CN ratio of MSW has
  increased over the years as the paper content has
  increased. A typical MSW ratio is now 601. To
  lower the CN ratio, the modern trend is to add
  sewage sludges. The following table describes
  the CN ratio of various materials.

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C/N Ratio of Various Wastes
Material C/N ratio
Night soil 6-10
Urine 0.8
Blood 3.0
Cow manure 18
Poultry manure 15
Horse manure 25
Raw Sewage sludge 11
Activated sludge 6
Grass clippings 12-15
Sawdust 200-500
MSW 60
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Co-composting Cont.

• Simple windrow facility to enclosed reactor
• Successful co-composting mixtures
• MSW organics / secondary sewage sludge
• Septage solids / wood chips
• Abattoir wastes / yard wastes
• Chicken manure / yard wastes
• MSW organics / septic tank pump out waste
• MSW organics / fishery wastes

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Typical Small Island State Operations

• Leachate left in the landfill, treated, recycled
  or released
• Landfill Gas ignored, passively vented
• Septage lagoon treatment, effluent discharged
• Screenings landfilled, dedicated disposal cells
• Sewage Sludge stored, land spread
• Other Residuals uncontrolled

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Caribbean Case Study- Bahamas

• New Providence
• New Providence Sanitary Landfill
• Operated by DEHS
• 60 mil HDPE Liner
• Leachate Collection
• Gas Collection Piping Installed
• Septage Sludge Facility
• Operated by WSC
• HDPE Liner
• Treats waste from septic tankpumpouts

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Present Situation in New Providence
Liquid Disposal(Deep Well)
Treatment(Lagoons - Future)
Landfill Leachate
Lagoons(Anaerobic/Aerobic)
Liquid Disposal(Deep Well)
Septage Sludge
Drying Beds(Future)
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Cooperative Approach
Septage Sludge
Septage Sludge
Recirculate
Recirculate
Or
Landfill
Landfill Leachate
Landfill
Landfill Leachate
Liquid Disposal (Deep Well)
Lagoons(Anaerobic/Aerobic)
Lagoons(Anaerobic/Aerobic)
Solids Disposal (Landfill)
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Caribbean Case Study - Barbados

• Current situation
• 9,000 m3 /day secondary wastewater treatment
  system at Bridgetown, producing primary and
  secondary sludges which are land spread.
• 9,000 m3/day advanced preliminary treatment plant
  for the South Coast, producing 750 kg /day of
  screenings, currently bagged and landfilled.
  In-situ incineration is planned, at an estimated
  capital cost of US1.0 million.

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Barbados Case Study Continued

• New engineered sanitary landfill (1.0 m of
  compacted clay liner) at Greenland with leachate
  collection and treatment capacity (anaerobic,
  facultative and aerobic lagoons in series). Built
  in 1997. Not yet in use.
• Current landfill at Mangrove being extended, with
  new cell having a composite liner and leachate
  collection system. However, leachate is
  currently being recirculated onto a section of
  the landfill that is not lined.
• Special wastes (abattoir wastes, grease)
  currently being land spread at another location.

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Too Many Cooks?

• In Barbados, the administration of waste
  management includes the following agencies
• Design of new landfill Sewerage Solid Waste
  Project (SSWPU) Ministry of Health
• Design of Extension to old Landfill Sanitation
  Services Authority (SSA) Min. of Health
• Operation of old landfill SSA
• Design and construction of the South Coast
  Sewerage Project (SCSP) SSWPU

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Too Many Cooks?

• Operation of the SCSP and the Bridgetown WWTP
  Barbados Water Authority Ministry of Utilities.
• Result not only are different agencies
  responsible for solid and liquid waste management
  but different agencies are responsible for design
  vs. operation. This is typical in the Caribbean
  with a notable exception being St. Vincent the
  Grenadines with the CWSA responsible for both
  solid and liquid waste.

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Recommended Synergistic Approach

• Dispose of residuals from the SCSP (screenings)
  by bagging and landfilling and abandon the
  incineration plan.
• Abandon the plan to build a separate mechanical
  treatment septage and sludge handling facility.
  Dispose of these residuals at the landfill and
  operate the new cell at the existing landfill as
  a bioreactor.
• Special wastes (blood and grease) can be
  co-composted with yard waste at the proposed
  national composting facility or added to the
  liquid stream recirculated to the bioreactor cell
  at the landfill.

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Conclusion Real World?

• Solutions can appear very simple on paper yet are
  little more complicated to implement in the real
  world
• On a daily basis, landfills, sewage treatment
  plants and septage and sludge facilities
  throughout the Caribbean continue to operate and
  generate residuals
• The responsibility for cost effective business
  practices rests on the shoulders of the General
  Managers and the Directors of these operating
  entities

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Conclusion

• It can be concluded that there is merit in
  investigating cooperative solutions that could
  result in cost savings, a higher level of
  environmental protection and reduced risk
• The benefits are numerous
• Residuals from one stream could benefit another
  system resulting in a useable end product
• Capital and operating costs could be reduced
• Risk of damage to the environment from the
  mismanagement of these residuals could be
  prevented

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• Thank you