prepared by A. C. Abino Laguna Lake Development Authority, Km. 70 Bangyas, Calauan, Laguna (E-mail: abinoazyleah@gmail.com) for Urban Environments in Asia, 25-28 May 2011, Manila, Philippines. organized by International Water Association (IWA).

1. Decentralized Wastewater Treatment System (DEWATS) for
the Sta. Cruz Class AA Municipal Abattoir
A. C. Abino
Laguna Lake Development Authority, Km. 70 Bangyas, Calauan, Laguna
(E-mail: abinoazyleah@gmail.com)
Abstract
Wastewater from slaughterhouses is mainly composed of diluted blood, fats, suspended solids and
in some cases manure. When untreated wastewater was discharged into creeks, rivers or lake, it
will contribute significant volume of Biochemical Oxygen Demand (BOD) and Chemical Oxygen
Demand (COD) of the receiving water body at a concentration of 1100 ppm and 2200-2500 ppm,
respectively. The Decentralized Wastewater System (DEWATS) is a treatment system that could
separate solids and stabilized pollutants, remove toxic or other hazardous substances which are
likely to distort sustainable biological cycles as well as stabilized or inactive suspended substances
in order to reduce BOD, COD and other parameters within the prescribed limits set under the
effluent standards for Class C waters. This wastewater system was applied to treat the effluent of
the Sta. Cruz Class AA Municipal Abattoir which started to operate on September 2009. Parallel
to its operation, wastewater samplings were conducted to establish and monitor system efficiency.
In cognizant to the performance of the cost-effective facility, samples analyzed obtained 37.33%
and 80.48% reduction of BOD and TSS, respectively, relative to the standards stipulated in DAO
No. 35. Apart from the treatment of effluent, the DEWATS is equipped with gas (CH4) recovery
system given that the wastewater quality is suitable for methane production. Through the
operation of the DEWATS being a low-cost natural treatment processes and efficient technology
for the Sta. Cruz Double AA Abattoir, the system was replicated by different LGUs within the
Laguna de Bay region under the LISCOP Project as a sanitation solution to mitigate further
pollution loading on the lake amidst the continuous economic growth and urbanization thereat.
Keywords
increasingly environmentally conscious economy; cost-effective and efficient technology;
methane recovery
RECOGNIZING NEED FOR CHANGE
Sta. Cruz is the provincial capital of Laguna which lies in the southeastern portion of the Laguna de
Bay Basin. Being a first class municipality and part of the economic growth corridor, the
CALABARZON, its population has continued to grow tremendously due to uncontrolled in-
migration from Metro Manila and other surrounding regions. These concerns have led to informal
settlements, urban sprawl, congestion and concomitantly, the growing range of environmental
issues and challenges for the Local Government Unit (LGU).
Over recent decades, livestock farming was among the growing industry and economic livelihood
in the municipality of Sta. Cruz. In fact, among the towns covered by the Sta. Cruz sub-basin, it
ranked first in terms of the population of livestock raised annually. It has even produced better
economic and livelihood opportunities for the constituents of Sta. Cruz. The municipality has even
become one of the centers for the production of meat and meat products in the region. The LGU
also was able to generate additional revenue from the establishment and operation of a Municipal
Abattoir within the public market. However, the operation of the slaughterhouse encountered
problems related to the management of effluents as well as compliance to environmental laws and
standards. To resolve these issues, the LGU decided to permanently close the old slaughterhouse
and construct a new municipal abattoir with wastewater treatment system in Barangay Palasan. The

2. LGU recognized that with affordable but effective sanitary controls, the availability of good quality
meat is ensured, however, spurred by an increasingly environmentally conscious economy, it has
been recognized that the cleanliness and sanitation of meats and other components that reach the
markets should not be made at the detriment of the environment.
COMMITMENT AT WORK
In 2005, wastewater management has been identified by the key stakeholders as one of the priority
concerns during the Laguna de Bay Watershed Environmental Action Planning (LEAP) under the
World Bank Funded, Laguna de Bay Institutional Strengthening and Community Participation
(LISCOP) Project. Through the LISCOP Project that is being implemented by the Laguna Lake
Development Authority (LLDA) through a loan from the World Bank and a supplemental grant
from the Government of Netherlands, DEWATS was installed on the newly constructed Sta. Cruz
Class AA Abattoir. The construction of the DEWATS will ensure compliance to the DENR and
LLDA effluent standards prior to their discharge into the Sta. Cruz river.
DEWATS MODULES
Basically, the treatment process allows the separation of solids and stabilize pollutants, removal of
toxic or other dangerous substances which are likely to distort sustainable biological cycles and the
removal of stabilized or inactive suspended substances in order to improve turbidity. The untreated
wastewater passes through series of engineered modules that involves anaerobic and aerobic
processes to be able to achieve the standards set by the regulatory institutions of the country. Figure
1.1 illustrates the perspective view and on-site photo of the DEWATS modules implemented for the
Sta. Cruz Class AA Municipal Abattoir.
Phragmites
IP PGF AF ABR Biogas Digester
Figure 1.1 DEWATS module in its perspective illustration (left) and on-site photo (right)
Biogas Digester
The first anaerobic module is the biogas digester. Its main purpose is for the utilization and
collection of biogas which is produced by means of fermentation/digestion of slaughterhouse waste.

3. Anaerobic Baffle Reactor
The baffle reactor forms part of the secondary anaerobic treatment which encompasses series of
chamber that functions to assist the digestion of difficult degradable substances by intensifying the
contact between the incoming raw wastewater and the active biomass present in the reactor.
Anaerobic Filter
Filter mediums such as volcanic cinders are used in order to allow the wastewater to circulate
passing the fixed microorganisms as a treatment process. It includes treatment for non settleable
solids and dissolved solids by bringing them in close contact with a surplus of active bacterial mass.
Planted Gravel Filter
This constructed wetland forms part the aerobic processes in treating the wastewater effluent. The
treatment is done through filtration and continuous oxygen supply to the upper layers providing
favourable environment for bacteria diversity. Suspended solids and colloidal suspended solids of
the pre-treated wastewater should be destroyed and removed before it traverses the planted gravel
filter to avert clogging and reduce the hydraulic conductivity of the filter. Phragmites (tambo) is the
plant species used in the reed bed since it provides a perfect root zone filter.
Indicator Pond
The main function of the pond is to expose the treated wastewater to ultraviolet rays to aerobically
degrade pollution, to remove pathogen and to monitor treated wastewater quality. Samples for
laboratory analysis are taken in this module.
COST-EFFECTIVE AND EFFICIENT TECHNOLOGY
Wastewater effluent from a slaughterhouse has a complex composition if not properly managed can
cause adverse impacts to the environment. It is stronger compared to domestic or municipal
wastewater because slaughterhouse wastewater is mainly composed of diluted blood, fat, suspended
solids and in some cases, also contains manure. When untreated wastewaters are released to water
bodies, it will contribute significant volume of Biological Oxygen Demand (BOD) and other
harmful substances that will pollute the receiving body of water. It was estimated that the BOD and
COD of influent was measured at 1100 ppm and 2200-2500 ppm, respectively.
The LGU of Sta. Cruz estimated that about 240 liters of water is being used to slaughter one head
of cattle and 120 liters per head of hog. However, when contaminated with blood and solids, it was
estimated to increase wastewater production by as much as 10% which is equivalent to 264 liters
for cattle and 132 liters for hogs.
The treatment plant was designed to treat 30m3 (daily peak quantity) of wastewater produced from
the abattoir. Likewise, the system has been customized to meet the effluent standards for Class C
inland waters specifically for New/Proposed Industry (TSS<70 mg/L and BOD5<50 mg/L) as
prescribed under DAO No. 35 or the Revised Effluent Regulations of 1990. The facility started to
operate on September 2009. Parallel to its operation, wastewater samplings were conducted to
establish and monitor system efficiency. Based on the results of the analyses of six (6) wastewater
samplings, BOD ranges only from 19mg/L to 40mg/L relative to the standard BOD limit of 50mg/L
which is illustrated in Figure 2.1.

4. Figure 2.1 Results of the analysis of BOD (mg/L) from the samples taken at the Indicator Pond of
the Sta. Cruz DEWATS
Moreover, findings for the TSS sampling revealed that the sound operation of the engineered
treatment facility which obtained readings within the array of 10mg/L to 19mg/L, is significantly
lower than the 70mg/L maximum allowable effluent standard. Figure 2.2 shows the results of the
six (6) samplings conducted.
Figure 2.2 Results of the analysis of TSS (mg/L) from the samples taken at the Indicator Pond of
the Sta. Cruz DEWATS
In cognizant to the performance of the cost-effective facility, samples analyzed obtained 37.33%
and 80.48% reduction of BOD and TSS, respectively, relative to the standards stipulated in DAO
No. 35. Furthermore, the law vested the LLDA with regulatory functions over the Laguna de Bay
region, which encompasses the municipality of Sta. Cruz traversed by a major tributary river
system, Sta. Cruz river, that flows to Laguna de Bay. Add to the construction of the DEWATS for
the Sta. Cruz Class AA Abattoir under the LISCOP Project which is implemented by the LLDA. A
further wastewater sampling was undertaken by the Environmental and Social Safeguards, a group
also forms part LISCOP Project, which the results tabulated below likewise show that all of the
effluent standard parameters were met by the treated effluent.

5. Table 1. Results of the analysis of effluent standard parameters from the samples taken at the
Indicator Pond of the Sta. Cruz DEWATS
Determinands Laboratory Sample Effluent Standard
pH 7.4 6.5 - 9.0
TSS, mg/L 9 70
BOD, mg/L 10 50
Oil/grease, mg/L 5 5
Apart from the treatment of effluent, the project had the potential to avert the emissions of methane,
a greenhouse gas. The treatment facility is equipped with gas (CH4) recovery system given that the
wastewater quality is suitable for methane production. Based on Philippine’s climatic conditions
and performance of the DEWATS biogas digester, each biogas digester is designed to treat a
maximum of 17 m3 of wastewater discharged daily with an estimated biogas production of 5.36
m3/day which is also equivalent to 0.22 LPG per day. Considering such data, it is therefore
calculated that through methane capture and combustion, the facility is able to save almost
Php3,000.00 from the purchase of LPG per month of operation. The methane captured was used by
the butchers for cooking which in the long run deemed to be used for the operation of the
slaughterhouse through a gas pipeline from the biogas digester to the boiling area.
SETTING THE BENCHMARK AND ADVANCING SUSTAINABILITY
The intended beneficiaries of the project, primarily, are the residents of Sta. Cruz, Laguna.
However, since the Sta. Cruz slaughterhouse is the only slaughterhouse within reach of some
towns, residents of nearby LGUs stand to benefit since with cleaner production from the
slaughterhouse as well as the realization of its environmental and socio-economic impacts, the
possibility of interruptions from environmental officials become less probable.
Through the operation of the DEWATS being a low-cost natural treatment processes and efficient
technology for the Sta. Cruz Double AA Abattoir, the system was adopted/replicated by different
LGUs within the Laguna de Bay region under the LISCOP Project as a sanitation solution to
mitigate further pollution loading on the lake. However, depending on the success of the waste
minimization techniques and the extent to which the plant will modify practices and some
equipment water usage, and consequently wastewater production can be reduced from 25% to as
much as 41%. Together, the facility ensure that the operations of the slaughterhouse will be
sustainable and the environmental impact on the Laguna de Bay basin will be diminished.
References
BNS - BORDA (Basic Needs Services Philippines Inc. in partnership with Bremen Overseas Research and
Development Association). (2008). Operation & Maintenance Guideline of Decentralized Wastewater Treatment
Systems for Sta. Cruz, Laguna Slaughterhouse. 7-9.
LLDA, Tetra Tech EM. (2005) Feasibility Study Report of the Wastewater Treatment Facility for the Municipal
Slaughterhouse of Sta. Cruz, Laguna. LLDA, Pasig City, Philippines.