Preliminary Investigation of appropriate options for Leachate and Septage Treatment for the
Caribbean Island of Antigua.
Tsukuba University
Graduate School of Life and Environmental
Sciences

Shaka K.Y. FRANCIS
Yoshiro HIGANO, Takeshi MIZUNOYA, Helmut
YABAR
Abstract

On the global scale, the single greatest factor contributing to marine pollution has been
identified as untreated wastewater entering the world’s oceans and seas. Within the Caribbean region,it has been similarly observed that sewage pollution from land based sources is the most pervasive
form of contamination of the coastal environment. For the Caribbean island of Antigua there is nocentralized sewage system. The majority of residences utilize the option of Septic Tanks as thepreferred option for onsite wastewater treatment. However, the systems in use are operated tovarying efficacies where improper design and poor soil conditions can result in septic tank effluent
going directly to public drains and eventually the sea. The potential environmental risks of effluent
discharge is further exacerbated by the fact that the septic tank derived sludge is routinely removed
and discharged untreated into the open environment at the local disposal site.
At the disposal site, the existing sanitary landfill produces leachate which is collected but eventuallyalso discharged into the environment without any prior treatment. The discharge of untreatedleachate and untreated septage at the same location suggests the possibility of a combined treatment
process to accommodate both waste streams.
The purpose of this paper is to examine the potential wastewater treatment options which can be
implemented in the setting of a tropical small island developing state.
Keywords: Caribbean Leachate Treatment, Septage, Landfill Leachate, Combined Septage Treatment
JEL classifications: Ecological Issues

Preliminary Investigation of appropriate options for Leachate and Septage Treatment for the
Caribbean Island of Antigua.
Tsukuba University
Graduate School of Life and Environmental
Sciences

Shaka K.Y. FRANCIS
Yoshiro HIGANO, Takeshi MIZUNOYA, Helmut
YABAR
1. Introduction

The single greatest factor contributing to global marine pollution has been identified as
untreated wastewater entering the world’s oceans and seas (UNEP/GPA, 2006). Within the Caribbean
region, it has been similarly observed that “sewage pollution from land sources and from ships has
been the most pervasive form of contamination of the coastal environment” (CARSEA, 2007). As is thecase for the Caribbean and other small island developing states, the growing standard of living andincreases in populations and industries such as tourism has resulted in increased waste water
generation with a concurrent trend for increased incidences of environmental degradation. As such,
waste water management is slowly coming to the fore as a key developmental issue within the wider
Caribbean region.
Throughout the Caribbean region, it has been estimated that less than 2% of urban sewage istreated prior to disposal (Emanuel, 2010). In the twin island nation of Antigua and Barbuda, there isno centralized sewerage system. The notable local attempts at collection and treatment systems arepackage plants principally used by Hotels of which 48% were characterized as being in “poor condition
or non-operational” (UNEP, 1998a). Individual treatment systems are utilized to varying degrees andefficacies, where the norm is for septic tank effluent to go directly to the sea (UNEP, 1998a). The
individual type systems used at the household level include the bucket system (a.k.a. night soil); pit
privy (a.k.a. pit latrine) and septic tank & soak-a-way system (UNEP, 1998b).
In Antigua and Barbuda, the thrust towards a concerted effort to mitigate against wastewater
related environmental effects is evidenced by the fact that Antigua has signed on to the Convention
for the Protection and Development of the Marine Environment in the Wider Caribbean Region (alsoknown as the Cartagena Convention) and the Protocol on the Control of Pollution from Land-Based
Sources and Activities (LBS Protocol).
As with Antigua, the wider Caribbean has had checkered results implementing and sustaining
adequate treatment and management options even with the recognition of the current limited
management practices and the potential risks to the environment. UNEP/ GPA reported in the 2006
State of the Marine Environment Report that significant financial constraints exist and that there is alack of adequate, affordable financing available for investments in wastewater management in the
Wider Caribbean Region. In addition to financial constraints, other substantial barriers exist:
inadequate national policies, laws and regulations; limited enforcement of existing laws andregulations; poor communication and collaboration between various sectors and agencies which
contributes to a fragmented approach to wastewater management; and limited awareness, knowledge
and understanding of appropriate, alternative and low cost wastewater treatment technologies. Other
limitations in technical capacity (e.g. in developing project proposals, operating and maintaining
treatment systems, and monitoring and analysing wastewater discharges and impacts) constrain
progress in effectively managing wastewater.
An additional problem amongst those Caribbean territories with conventional treatment
technologies is the issue of sustainability. The conventional centralized systems generally use large
amounts of scarce water resources to flush domestic wastewater out of residential areas. In turn, thewastewater must be treated and the cost of treatment increases as the flow increases. Another reason

many treatment systems in the region are not successful is that they were copied from treatment
systems in developed countries without considering the appropriateness of the technology for theculture, land, and climate. In the end, many of the implemented installations were abandoned due tothe high cost of running the system and repairs, and the lack of technical capacity to properly operate
and maintain these systems.

In Antigua, a unique opportunity exists wherein household septic tank derived sludge(septage) and night soil are collectively disposed untreated at the sole authorised disposal site formunicipal solid waste i.e. the Cooks Sanitary Landfill and Disposal Site. At this sanitary landfill, thecollected municipal solid waste leachate is collected, stored and routinely released into the adjacentenvironment without treatment. Due to the proximity of the two liquid waste streams and thepotential environmental risks associated with their untreated release into the environment, the paper
will seek to investigate viable and appropriate technologies for separate or combined treatment of
septage and leachate.
2. BackgroundThe nation of Antigua and Barbuda is a twin island state within the North-eastern Caribbean.
The country is made up of 2 larger inhabited islands and a few other smaller islets. Of the inhabitedislands, the larger island of Antigua is 108 square miles (280 sq. km) in size and the smaller island of
Barbuda is 62 square miles (160 sq. km) in size. The estimated resident population of the nation is85,567 with a total of 83,922 living in Antigua and 1,645 living in Barbuda. Including visitors, thepopulation is recorded as 88,566 persons (Government of Antigua and Barbuda, 2014). Atypical forislands of the Lesser Antilles, Antigua and Barbuda is characteristically absent of the dense tropicalforests, rivers, expansive watersheds and mountainous landscapes which are generally attributed tothe tropical climes of the region. Both islands are exposed to a tropical marine climate, with strong
influence of the northeasterly trade Winds, constant high temperatures, and a very marked Wet andDry season.
There is little variation in temperature throughout the year but very variable levels of
precipitation. Average monthly minimum temperatures range from 22.4oC in February to 25.4oC in
August, while monthly maximum temperatures range from 27.9oC in February to 30.5oC in September(Cooper & Bowen, 2001) As given by the Antigua and Barbuda Meteorological Office, the averageannual rainfall for Antigua is 1203.6mm (for the period 1981 – 2010) however there is a seasonal
striation pattern wherein the precipitation is highest during the months of August to December (wetseason) and lowest between January and April (dry season) (Cooper & Bowen, 2001)
The extremely variable levels of rainfall coupled with erratic distribution and limited surface
or ground water storage areas have combined to produce recurring scenarios where precipitation is
insufficient to meet economic, social and environmental demands (Cooper & Bowen, 2001). Antigua is
one of the most arid islands in the region, has droughts every 3 to 7 years, and where desalination is
the largest contributor (>70%) to the national potable water system (PAHO, 2012). Barbuda isconsiderably drier compared to Antigua, with an average annual precipitation of 750mm to 900mm
for the period 1965 – 2000 (Organisastion of American States, 2001). The high temperatures and local
wind patterns give rise to relatively high evapotranspiration rates which has been reported to normallyexceed effective precipitation in 11 months of the year (Cooper & Bowen, 2001). However, in theabsence of specific monthly values for local evapotranspiration data, for the purposes of the paper,
the conservative estimate evapotranspiration rate is taken as 70%.

The country is heavily dependent on tourism as the main driver of the economy, withestimates suggesting it accounts for between 60% (Cooper & Bowen, 2001) to 62.9% of the national
GDP (World Travel and Tourism Council , 2014). According to the Pan American Health Organisation(PAHO), the per capita waste generation rate is given as 1.75kg/person/day with “evidence that thetransient (tourist) population probably contributing to this generation rate” (PAHO, 2004). From
records of the National Solid Waste Management Authority, the annual volumes of household waste
and septage disposed in Antigua are captured in Table 1.
Table 1. Waste received at the Cooks Sanitary Landfill and Civic Amenities Site

Year
2006
2007
2008
2009
2010
2011
2012
2013
2014

Waste Category
Household
Septage
Waste (Tonnes) (Tonnes)
20518.94
12177.96
20790.74
16908.18
22964.02
16551
22682.52
13312.44
24272.3
10746.34
22331.86
11387.32
20918.78
13300.78
20964.21
13862.65
20909.04
15312.93

Whereas the household waste is disposed of in the 2.43 hectare sanitary landfill cell, the septage
is disposed of by burial in earthern pits or trenches at the adjacent unlined bulk waste dump site. The
leachate generated from the decomposing household waste, though collected, is untreated as is thecase for the septage and both waste streams eventually enter the swampland surrounding the disposalsite.
3. Methodology and Results
For the purpose of the paper, the term “Appropriate Technology” will be defined as technologythat is affordable, and operable by the user and that reliably provides the needed degree of purification(UNEP, 1998a). As an extension of the affordability and operability criteria, consideration of themaintenance costs, consumables restocking costs, energy costs and land space requirements will be
critical factors in the decision making process.
3.1 Septage loads
Over the period 2010 to 2014, the annual volume of septage recorded as received for disposal in
Antigua has been on the increase (Figure 1). The fluctuations of septage volumes within a year (2012)is illustrated in Figure 2 to establish the seasonal variations of waste flow rates. Apart from volumetricdata, there is sparse data on the physical and chemical properties of the septage reaching the local
disposal site. In the absence of such data, certain approximations had to be made for the design
parameters (Table 2). Comparing literature data from the US EPA with regional data on the typicalpollutant composition of septage, the design criteria was created using the upper values from the two
characterisations.

Figure 1. Annual septage volumes for Antigua

Figure 2. Monthly septage disposal values

Table 2. Typical and proposed concentrations of pollutant substances in Septage

Septage Constituent

Biochemical Oxygen Demand(BOD)
Chemical Oxygen Demand(COD)
Total Kjeldahl Nitrogen (TKN)
Ammonia Nitrogen (NH3 – N)
Total Phosphorus
Fats, oil, and grease
Alkalinity
Total Solids (TS)Total Volatile Solids (TVS)
Total Suspended Solids (TSS)
Total Volatile Suspended
Solids (VSS)

TypicalConcentration1(mg/L)

Design Criteria(mg/L)

6,500

Typical CaribbeanspecificConcentration2(mg/L)
5,000

30,00040,00040,000

600
100
210
5,600
1,000
34,00025,00015,0009,000

700
Not stated
300
7,500
Not stated
Not stated
Not stated
25,000Not stated

700
100
300
7,500
1000
34000
25000
25000
9000

6,500

3.2 Leachate Loads
At the Cooks Sanitary Landfill, there are no records of neither the volume nor chemicalcomposition of the landfill effluent. To estimate leachate production, consideration had to be given to
rainfall totals, surface runoff, rainwater seepage and the landfill operational practices such as the sizeof the tipping face area, compaction equipment used and daily waste cover percentage etc.
In calculating leachate generation from a sanitary landfill, the degree of rainfall infiltration isconsidered the principle contributing factor (Fenn, Hanley, & Degare, 1975). In Antigua, the mean
monthly precipitation ranges between 51.8mm and 149.4mm with an annual mean rainfall of
1,203.6mm. Evapotranspiration is conservatively taken as 70% of precipitation, which translates into
an annual loss of 842.52mm per year to evapotranspiration. As a result, the annual effective rainfall isthus calculated as 361.08mm. For sensitivity purposes, the maximum annual effective rainfall possible
during a year (precipitation equal to the maximum observed historical value) is calculated at529.23mm.
The estimation of leachate flow was compiled using the formula (Government of Hong Kong,
2007):For the purposes of the paper it was assumed that the runoff coefficient for the landfill is 0.7 (i.e.
70% of surface water infiltrates into the leachate collection system). The operation area was given as

1

U.S. EPA. 1984. Handbook: Septage treatment and disposal. EPA/625/6-84/009. Cincinnati, OH.
UNEP, 1998. Appropriate Technology for Sewage Pollution Control in the Wider Caribbean Region. CEP
Technical Report No. 40. UNEP Caribbean Environment Programme, Kingston
2

15,600m2 per year3. As such, taking the maximum annual effective rainfall figure of 529.23mm into
consideration, the volume of leachate projected is 5779.19m3
The only accessible data on leachate characteristics for Antigua were from two analyses in 2009and one from 2010 to assess the composition of the stabilised leachate in the storage ponds (Table 3).
That exercise was to facilitate an assessment prior to discharge of the leachate into the surrounding
wetlands. To date, these were the only records where any analyses were completed prior to discharge.
There are no records for the composition of fresh leachate from the landfill. As such the design value
for the investigation (Table 3) was taken as an average of some extreme values for the composition ofleachate developed through a review of technical literature (Meeroff & Teegavarapu, 2010)
Table 3.Concentration of pollutants in stabilised Antiguan leachate, design values for future projections

pH
COD [mg/l]
BOD5 [mg/l]
Ammonia-N [mg/l]
TKN (mg/l)
PO4-P [mg/l]
Phosphates (mg/l)
TSS (mg/l)
Lead [µg/l]
Conductivity (µS/cm)
DO (mg/l)
Nitrate (mg/l)

Analysisfrom
3.6.09Analysisfrom
19.6.09

Analysisfrom
10.5.10

DesignValue

7.96 9.44
47.1 64.8
0 - 33

7.84 - 9.39

7.9 - 9.0

7.5
10,30022 - 35

0 - 12.7

4,000
830

0.09 2.75

6 - 120840
0.1
13,1001.15 4.56
0.0 - 9.9
0 - 17.1

8.4 - 29.8

3.3 Effluent Limits
Antigua and Barbuda has no established effluent quality criteria for effluent discharge to the sea,
but adopts regional standards. In 1998, the Caribbean Environmental Health Institute (CEHI) suggested
new regional guidelines (Table 4) for effluent quality including discharge limits for ecologically sensitive
areas4. Considering the potential application of treated wastewater for some degree of reuse, the US
EPA guidelines were also considered.

3

Using a 20m * 15m area as the weekly Tipping Face.
Areas susceptible to degradation or destruction by human activities, due to inherent and/or uniqueenvironmental characteristics and/or a fragile biological or ecological situation.
4

Table 4. Parameters and standards for domestic and industrial wastewater discharges (Adapted from UNEP, 1998)

Parameter

CEHI Standard for NonSensitive Waters

CEHI Standard for Sensitive Waters

Total
Suspended
Solids

100 mg/L

30 mg/L< 30mg/L

Biochemical
OxygenDemand (5day)

150 mg/L

30 mg/L< 30mg/L

COD

300 mg/L

150 mg/L

FaecalColiform

No standard
established

43 MPN/100 mL in shellfish harvestingareas
200 MPN/100 mL in all other areas

Total
Inorganic
NitrogenNo standard
established

10 mg/L in nutrient sensitive waters

SolublePhosphorus

No standard
established

1 mg/L in nutrient sensitive waterspH

6 to 106 to 10

Fats, Oils,
And Greases

50 mg/L

2 mg/LAmmonia as
N

No standard
established

5 mg/L

Total Chlorine
Residual

No standard
established

0.1 mg/L

No visible floatables

No visible floatables

Floatables

US EPA Standard for
Restricted Urban reuse< 200 MPN/100mL

6 to 91 mg/L4. Discussion
As a result of the unavailability of locally specific data on the physiochemical characteristics of bothleachate and Septage in Antigua, certain assumptions and approximations had to be made in
conducting this exercise. The literature data used for the design values in the preceding sections, could
be significantly different from the local scenario. Furthermore, in the case of Septage arriving at the
Cooks Disposal Site, it is expected that even between loads arriving by vacuum tank, the composition
would show great variability. The septage variability could be attributed to differences between
household sizes, septic tank construction, pumping frequency, users’ water usage habits etc. For

leachate, the variability could be attributed to waste age, waste composition, compaction rates,climatic changes and temperature. It must therefore be noted that even with the best guessapproximations sourced from literature reviews and case studies, the site specificity and temporal
specific of each locale, would imply that the calculations and projections can only be used as
approximations of actual conditions.
In considering options for treatment, the local dynamics of climate, social economics, availabilityof human resources, replicability, and general “appropriateness” were the considered factors. The
proposed technologies and processes have been detailed in Table 5 below. For the proposed
combined treatment processes, reference was made to work done in Taiwan to examine thetreatment efficiency of anaerobic digesters (Lin, Bian, & Chou, 1998) and the suitability of using a
UASB reactor (Lin, Chang, & Chang, 1999). For all proposed options the treatment efficiency is
obviously dependent on the initial influent quality and composition.

Individual Leachate Treatment

Table 5. Options for treatment of municipal solid waste landfill leachate and septage for Antigua. Adapted from (Meeroff D,2010) and (US EPA,1984)

Treatment Process

Advantages

Disadvantages

Evaporation: use ofshallow lined ponds
to reduce liquidvolume.

 Great for arid regions like
Antigua with highevapotranspiration rates
 Efficient on COD
 Efficient on Ammonia
 Efficient on inorganics
 One of least expensive
options Rumoured to be theinitially proposed option
for Antigua in the landfill
design stages
 Efficient on COD
 Efficient on BOD5
 Efficient on Ammonia
 Efficient on inorganics
 Small space requirement
 Used at the sanitary
landfill site in theneighbouring island of St.
Lucia.
 Efficient for BOD5
 Relatively rapid treatment(>90% removal of BOD5 in
6‐8 hours)
 Minimal odour concerns

 Post treatment ofresiduals required Large space requirement

Re-circulation:
reinject theleachate back into
the landfill

Aerated Lagoon,
Extended Aeration:use of mechanicalaerators to create amixed culture
microbial
environment.

 Efficiency is dependent
on initial leachate quality
 Performance is highlyvariable and site specific Post treatment may berequired Treatment performanceis highly variable and may
require pre-treatment
 Does not address bio‐
toxics Potentially large sludge
 production
 Potentially large energy
requirements
 Does not address TDS or
conductivity

Individual Septage Treatment
Combined Treatment ofLeachate and Septage

Lime/coagulant pretreatment &Activated Sludge

Lime pre-treatment can be: Efficient on COD
 Efficient on inorganics
 Efficient on TSS
 Disinfectant
 Effective in reducing
biotoxic substances
Activated sludge systems canbe: Effective on removal of
BOD, nutrients andammonia

Lime pre-treatment can be: Efficient on COD
 Efficient on inorganics
 Efficient on TSS
 Some disinfection
actionActivated sludge systems
can exhibit:
 Longer aeration times(energy demand) Fluctuating leachate
quantity and quality
can affectperformance Excess sludge
production

Lime Stabilisation

 Low capital costs
 Simple technology
 Potential pathogen
reduction
 May reduce nitrogenconcentration
 Relatively low capital costs
 Technology in use locallyat package plants
 Relatively easier tooperate compared toanaerobic treatment
 Produce an odourless,stable residual that is easy
to dewater Smaller footprint Production of methanegas Poor quality supernatant
after the anaerobic phasecan be addressed by theaeration phase Combined waste streams
to improve the economy
of scale High pH effluent
 No reduction of organics
 Increased sludge
production

 Combined waste streams
to improve the economy
of scale Ammonia content of theleachate can affectremoval rates of total
COD, soluble COD, total
solids, and volatile solids(Lin, C.Y., 2000)

Activated Sludge

Anaerobic digestion
and aeration of
effluent

Coagulation ofleachate &Activated Sludge
Upflow anaerobic
sludge blanket

 Potential foaming
problems.
 Energy requirements for
aeration Relatively high capitalcosts
 Sensitive to upsets Large footprint Energy requirements for
aeration5. Conclusion
As a small island developing state, Antigua is faced with the challenges of increasing standardof living, increases in populations and industries such as tourism and a resultant increase in liquid
waste generation. The proposals detailed in the paper are a combination of low cost, lowtechnology, or otherwise viable options for individual or combined treatment of Leachate andSeptage at the local disposal site. Of the proposed treatment processes, the options with thegreatest likelihood of success will be the options most compatible with the island’s climatic andsocio economic nuances. The viability of any option or combination thereof, will have to beaddressed by a subsequent feasibility analysis which was beyond the scope of this paper. In
conjunction with the future feasibility analysis, expansion of the design criteria could include
utilising renewable energy (such as solar or wind powered aerators) for subsequent considerationof energy balance in the feasibility assessment.

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