Title: Opportunities for Sectoral Synergy in Public Sector Waste Management UNDP Waste Management Experts Meeting Havana, Cuba, October 27 - 31, 2003
1Opportunities 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.
2Introduction
- 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.
3Cooperative Approach
Economic Benefits
EnvironmentalBenefits
Risk ManagementBenefits
Result Improved Operation and Reduced Costs
4Constraints 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.
5Constraints 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.
6Technology Evolution
Engineered Sanitary Landfills Complex Mechanical
Treatment Plants
Higher Level of Environmental Protection
7Objective
- 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.
8Waste Streams Residuals
A List
B List
9Residuals (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
10Other Residuals
- Grease from food preparation
- Used motor oil
- Sludges from car washes
- Blood and by-products from abattoirs
- Manure
- Petroleum contaminated soils
11Disposal 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
12Disposal 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
13Disposal Options for Residuals
- Septage
- Series of lagoons settling pond, anaerobic and
aerobic - Incorporated into Primary Sludge disposal
14Disposal 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
15Disposal Options for Residuals
- Screenings
- Dedicated cells
- Landfilled
- Co-composting
16Synergistic Residuals Management Options
- The following two technologies may provide
opportunities for co-disposal of residuals in the
Caribbean - Bioreactor Landfill
- Co-composting
17Bioreactor 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
18Bioreactor 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.
19Leachate Generation
Estimated Leachate Generation Quantities New
Providence
20Co-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.
21C/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
22Co-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
23Typical 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
24Caribbean 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
25Present 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)
26Cooperative 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)
27Caribbean 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.
28Barbados 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.
29Too 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
30Too 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.
31Recommended 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.
32Conclusion 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
33Conclusion
- 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
34