THE CONSTRUCTED TREATMENT WETLAND PROJECT OF BAYAWAN CITY:
A PIONEERING VENTURE BY A LOCAL GOVERNMENT UNIT
IN WASTEWATER AND ENVIRONMENTAL MANAGEMENT
INTRODUCTION
Bayawan City is located in the 3rd Congressional District of the Province of Oriental Negros and
encompasses a total land area of 69,908 hectares composed of 28 barangays. It became a chartered city
on December, 2000 and is now poised to become the economic hub in the southwestern part of the
province. Current population is estimated at 105,000 with an average annual growth rate of 2.59%. With
its vast land and marine resources, the city envisions of being “The Agriculture Capital of the Province,”
and is keen on developing agriculturally based industries to spur economic growth and progress in the
countryside.
One of the earliest flagship projects that the city government undertook was the construction of a
new road that would traverse the coastal areas in the urban district. The new road was meant not only to
decongest traffic in the main highway and open up new areas for commercial development, but more
importantly, to address the blight and state of deterioration befalling the urban coastal area due to the
unabated build up of informal settlers. To pave the way for the road construction, the city procured a 7.4
hectare lot along the proposed route of the coastal road to serve as the site for a housing project to be built
for the informal settlers affected by the road opening.
In the course of implementing the housing project, the city government realized that in order to
comply with the provisions of the Philippine Clean Water Act of 2004, as well as the conditions required
in the Certificate of Environmental Compliance issued by the Department of Environment and Natural
Resources, sewage collection and wastewater treatment facilities had to be incorporated in the design and
construction of the housing project components.
To meet the challenge, the city turned to the German Agency for Technical Cooperation (GTZ),
thru the Department of the Interior and Local Government (DILG), for assistance. The relatively novel
concept that the GTZ presented—recovery and re-use of wastewater as a resource—was keenly
welcomed by the City Government as a versatile and holistic approach that was consistent with the
development goals of the city, and in achieving a healthy, productive, and sustainable balance between
man and his environment.
OVERVIEW OF CONSTRUCTED TREATMENT WETLAND TECHNOLOGY
The advantages and desirability of a Constructed Treatment Wetland (CTW) can be appreciated
best by understanding how natural wetlands function / work. Wetlands are defined as areas that are
inundated or saturated by surface or groundwater at a frequency and duration sufficient to support a
prevalence of vegetation adapted for life in saturated soil conditions. Marshes, bogs, swamps, and
mangroves are some forms of natural wetlands. Long considered as natural water purifiers, wetlands
degrade most forms of organic matter to carbon dioxide and release trace elements in the process.
Pollutants are trapped and broken down into elemental compounds by the complex biology and chemistry
of wetland plants. Dense growth of vascular plants that thrive in wetland, along with the slow flow of
water, create microenvironments that provide microbial community attachment sites.
Constructed wetlands are engineered wastewater treatment systems comprised of cells filled with
porous media (soil / sand / gravel) that are sealed to the subsoil and planted with aquatic and emergent
wetland plants like reeds. They are designed to maximize the physical, chemical, and biological abilities
of natural wetlands to reduce biochemical oxygen demand (BOD), total suspended solids, pathogens, and
other harmful substances, as wastewater flows slowly through the vegetated surface. The media serves as
a filter and absorbs contaminants. The plants, thru their stems, facilitate the entry of oxygen to the root
systems, enabling the growth of aerobic colonies in the root zone. Organic or pollutant load is absorbed
by the plant’s root system where they are broken down into simple components of water and gas.
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DESIGN FEATURES OF THE BAYAWAN CTW
The Bayawan treatment facility is a combination of the Vertical Soil Filter and the Horizontal
Soil Filter types of wetland systems:
Vertical system type – the wastewater is applied on the surface of the soil filter. By the
infiltration process, air is sucked into the pores of the filter material, supplying oxygen for the bacteria
which thrive as a biological film around the sand particles. Upon passing the filter layer, the water is
treated not only by microbial activity but also by adsorption. A critical aspect of this system is the rapid
and even distribution of a high amount of water. This requires a big pump or tank above the surface of
the filter bed.
Horizontal type – the water flows horizontally through a gravel or sand bed of 0.4 – 0.6 meters
thick which is planted with marsh plants. The microbial growth takes place on the surface of the gravel
and the plant roots. The plants supply some oxygen thru their roots which is used by the micro organisms
for aerobic breakdown of the contaminants. Although aeration is not as good as the vertical type, the
advantage of this system is that water can be applied continuously without using a pump or mechanical
flushing devises.
The primary treatment system is composed of several onsite three-chambered septic tanks shared
by household a cluster of 10 houses each and are distributed across the entire area of the village. Fresh
sewage from the toilets, bathrooms, and kitchen sinks / and drainage canals are partially treated in the
septic tanks reducing the biological demand and solids content. The overflow from these tanks is
collected by gravity through pipes to a main sump for storage and further removal of solids.
From the main sump, the wastewater is fed to a series of two cells or beds which are planted with
a locally abundant weed known as “tabon-ak” (Phragmites spp). Influent from the main sump is pumped
to several smaller header tanks that are connected to a network of distribution pipes deployed across the
first cell. As it percolates down the root-sand media, it is collected at the bottom layer of the bed by a
network of perforated pipes which discharge into a small sump at one corner of the cell. From here, the
wastewater is transferred by gravity to the 2nd cell. This cell could also be operated as a vertical flow
system during high volumes of discharges. The effluent from the 2 nd bed is then collected in another
sump from which the treated water may be re-used or re-circulated to the system for further polishing, or
disposed of in a nearby outfall to the sea.
Table 1. Basic Design Assumptions for the Bayawan CTW
No. of households
738
Persons per household
5
Total population at full occupancy
3,690
Per capita WW generation rate
50 L/cap/day
Total WW generation flow rate
184.5 m3/day
Design hydraulic loading
50 L/Pop. Equiv.
BOD concentration
300 mg/L
Total BOD load
55.35 kg/day
Area of Cell 1
1,800 m2
Area of Cell 2
880 m2
Area per population equivalent
1 m2
Hydraulic load
102.5 L/ m2
BOD load
30.7 g/ m2
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BENEFICIARIES OF THE PROJECT
The Fishermen’s Gawad Kalinga Village, a socialized housing project located within a 7.4
hectare property acquired by the city in Barangay Villareal, is intended for the households or families that
have been identified as the informal settlers that would be displaced by the road opening along the urban
coastal area. About 738 dwelling units are proposed to be built and targeted for completion by the end of
2007. The housing project is jointly undertaken with the Gawad Kalinga (GK), a church-based anti
poverty movement advocating values based community building programs. One of the livelihood
projects recently introduced is a vegetable production using organic farming methods. Treated water
from the constructed wetland is now used to irrigate the crops.
Treated water from the CW shall also be harnessed for the following uses and applications:
1.
2.
3.
4.
5.
Fire trucks / firefighting
Irrigation and watering
Toilet flushing
Housekeeping and maintenance of government facilities
Construction
The local government unit also stands to benefit from the project in terms of effective utilization
of its financial resources in the sense that constructed wetlands can be built with lesser expense than
conventional treatment options. CW are easy to maintain since they do not require complicated
equipment or machinery and expensive chemicals, requires less energy, and can be constructed using
local materials.
By duplicating the physical, chemical, and biological processes of the natural wetland ecosystem,
CWs are also to some extent, natural environments. As such, it can even be a potential wildlife site that
can provide habitat. A CW is also a public attraction and a highly effective tool for environmental and
educational activities.
In view of all these benefits, and considering the city’s advantage in terms of availability of land
and space, the City Government shall put up five additional Constructed Treatment Wetland facilities in
strategic areas of the city, starting with a 130 square meter facility for the exclusive use of the District
Hospital.
PROJECT COST AND IMPLMENTATION
Based on records from the City Engineer’s Office, the total cost of the CTW built for the GK
housing project amounted to Php 9,706,596.00 broken down as follows:
Construction Materials……………………………..P 5,504,780.00
Labor………..……………………………………… 1,809,500.00
Fuel………………………………………………… 986,816.00
Consultancy Services……………………………… 405,500.00
Contingencies………………………………………. 1,000,000.00
Total
P 9,706,596.00
===========
Per Capita Cost for full occupancy
after completion of the housing project: ……….P
2,630.51
Initial discussions with the representatives of the GTZ’s Water and Sanitation Program were
conducted in the later part of 2004 to set the preparations for various preliminary activities in the conduct
of the project implementation by the main collaborators.
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Thereafter, series of missions were carried out by GTZ experts to survey the project site and to
gather data and information regarding the health situation, water quality, and other technical data needed
for the draft plans of the wetland treatment system. The LGU’s capability and potential to implement and
manage the project were also assessed.
In April of 2005, the partnership between the City Government of Bayawan and the GTZ, was
formally sealed with a Memorandum of Agreement providing technical assistance in the construction of a
wetland treatment facility. With the favorable findings by the GTZ on local capability and the general
conditions in the locality, the final detailed plans of the project were finally submitted and adopted.
Having secured the legal and financial requirements, the City Mayor soon directed the City
Engineering Office to organize the Project Management Team (PMT). This team executed the different
components of the project including the mobilization of various stakeholders and concerned agencies –
both government and private entities.
The GTZ experts and local consultants continued to conduct knowledge transfer and capability
building exercises through workshops, training, and orientation of the personnel involved. The social
preparation component of the Gawad Kalinga in orienting the beneficiary settlers was also tapped by the
Project Team in educating the would-be beneficiaries about the principles of the wetland treatment
system.
Towards the final stages of the construction, the PMT began to organize the teams that would be
involved in the operations and maintenance of the system.
SUSTAINABILITY
The draft of the Operations and Maintenance manual was presented to the various teams, village
residents and the local leadership for review, critique, and suggestions that can improve procedures and
address problems that might have been overlooked. With able guidance from the foreign and local
experts and consultants, a final version of the manual was finally adopted by all the stakeholders. This
covenant is essential in defining the roles and functions of the operators, users, and implementers of the
wastewater treatment project.
O & M Teams
1) Field Operations Team – Takes care of the day-to-day operations of the system which covers
tasks related to the following:




Pumping and distribution; wastewater feeding schedule; recirculation
Management of treated effluent
Management of plants / vegetation
Site security and record keeping of daily activities
2) Engineering and Maintenance




Inspection and repair of electrical lines, pumps, and other equipment
Regular inspection and clearing of piping system
Regular inspection and cleaning of wastewater pretreatment collection system
Emergency engineering work
3) Water Quality Monitoring Team


Effluent Sampling and Analysis
Compile database on water quality analysis and submit findings / recommendations
to the Project Coordinator for appropriate action.
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4) Community Relations Team – A continuous information, education, and communication
campaign shall be undertaken especially as new batches of beneficiaries are settled in the
housing project. The main objective would be to control the quantity and quality of the raw
sewage that would be generated. Excessive water use would result to higher hydraulic
demands on the system, while quality would have a direct effect on the treatment efficiency.
Some household substances that can affect efficiency are: detergents, bleaching products,
chlorides, oil and grease, insecticides, and solvents.
Additional measure for sustainability is the designation of a Pollution Control Officer in the City
Government, who at the same time, also acts as the over-all coordinator. Various Cluster Heads of the
housing association are also members in the various O & M teams.
CONCLUSION
The launching and inauguration of the CTW facility at the Fishermen’s GK Village on September
4, 2006 is a landmark testimony to the common vision of the City Government of Bayawan and the
German Agency for Technical Cooperation to achieve a cleaner environment and healthier population.
There is little doubt that water-borne diseases and water-related health problems are mostly due to
inadequate and improper management of water resources. Water is fundamental to socio-economic
development and for maintaining healthy ecosystems, thus the imperative to deal with problems relating
to water quality management. The City Government’s commitment to ensure the sustainability of the
project will also set the pace for the replication of similar treatment facilities in five other areas in the city.
The turnover of the project to the beneficiaries also signals the turn of a new leaf in the city’s ongoing health and environmental initiatives. Although already tested and proven in many areas, the
Constructed Wetland technology is still not perfect. Design variables and parameters are unique to
specific locations. Constant monitoring and evaluation will be the norm, along with relevant research and
development. But that is the essence: The privilege and opportunity to work along and together with
nature… to make the world a better place.
Proposed Sites of
Wastewater Treatment
Facility in Bayawan
City
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Cr
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4
Di vers i on Road
City nt
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Bayawan
District Hopital
2
1
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City
National Highway
RI
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Hi
3
wa
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Proper
Fishermen’s
Village
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Ba
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a
l Ro
d
Sulu Sea
FlowDiagram
Water supply (BAWAD) & shallow wells
Septic Tank
Reed Bed 1
(Vertical Flow)
Reed Bed 2
(Horizontal Flow)
RECIRCULATE Treated Effluent
RE-USE
FIREFIGHTING/DISPOSAL
(Marine Outfall)
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Septic Tank
Main Sump
HORIZONTAL FLOW REED BED
By:
GERMAN P. SARAÑA, JR
City Mayor
City of Bayawan
Province of Oriental Negros
2nd Floor, City Hall Compound
Poblacion, Bayawan City
Telefax:(035)531-0020/ 531-0021 / 228-3131;
Website: http://www.bayawancity.gov.ph
e-mail address: mayor@bayawancity.gov.ph
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