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EPA Demonstrates a
Viable and Sustainable Technology to
Treat Wastewater in Central America

Louis Salguero (Project Leader)
Bruce Henry (Design Engineer)
Antonio Quinones (Technical Advisor)
US-EPA, Region 4, SESD, Athens, Georgia

ABSTRACT

In May 2000, a pilot wastewater treatment system was placed into operation in the town of Puerto Barrios, Guatemala to treat sewage that has been discharged untreated directly into ditches and rivers that flowed through the town. Traditional wastewater collection systems would have been very expensive to install. Through the joint efforts of several agencies, the wastewater treatment pilot project was built to serve 200 people and demonstrate the viability of alternative and appropriate wastewater treatment systems for the Central American region. The system has been operational for over a year and is providing excellent treatment.

INTRODUCTION

In February 1998, the people of Puerto Barrios requested assistance from United States Agency for International Development (USAID) in solving their wastewater problem. The port town, located on the eastern coast of Guatemala next to the Gulf of Honduras, has a population of approximately 60,000. Because there was no sewage collection system in the town, untreated sewage was discharged into the ditches and rivers that flowed through town and emptied into Amatique Bay. Children played alongside and in the rivers and ditches which were usually stagnant and contained decaying organic matter. These ditches are flushed only during storm events. Additionally, potable water lines were located in the contaminated ditches, and this promoted dysentery and other wastewater related health problems. Wastewater treatment was, therefore, not only necessary to address the environmental issues, but more importantly, was needed to improve the health of the community.

The project was a joint effort of the USAID, Central American Programs office in Guatemala (GCAP), and the United States Environmental Protection Agency (USEPA) Region 4 in Atlanta, Georgia. The Cooperative Housing Foundation (CHF) provided local logistical and organizational support for the project through USAID's Local Environmental Policy and Program Initiative (LEPPI). The LEPPI program incorporated the local community by forming an environmental committee of several community representatives who were asked to prioritize the environmental problems in their community and assist in solving those problems. This partnership began the process of giving ownership for the project to the community. The municipality provided the land for the project site and paid for part of the collection system.

DISCUSSION

In 1997, through a USAID-USEPA interagency agreement, USEPA personnel began providing technical assistance to USAID in addressing some of the environmental problems of the Central American Region. The USEPA, Region 4, Science and Ecosystem Support Division and Water Management Division assisted by evaluating wastewater problems. After visiting several Central American countries, one important finding was that a majority of the existing wastewater treatment plants were not operational. Based on information from local engineers, it became apparent that conventional wastewater treatment technologies were too expensive and complicated for the developing countries to operate. The more desirable approach was to use appropriate technologies that were low in operation and maintenance costs and required minimal technical expertise to operate. To introduce the concept of appropriate wastewater treatment systems to the region, a pilot wastewater treatment plant was installed in the town of Puerto Barrios, Guatemala. Complicating the situation was the fact that the ground water table in some areas was only a foot below the ground surface. Soils were compressible clays and unstable. Traditional collection systems would have been very expensive to install. If a collection system and a wastewater treatment plant could be made to work in that city, then it could serve as an example for the rest of the region.

The pilot project incorporated the use of two wastewater treatment plants (WWTP), each with a design flow of 5000 gallons per day (gpd). Each WWTP could treat wastewater from approximately 100 people. The wastewater treatment pilot project was built utilizing septic tanks at the homes in conjunction with a collection system that utilizes small diameter gravity sewers (SDGS). The SDGS utilized four-inch diameter lines to transport the septage from the septic tanks to a pumping station. The pumped wastewater is treated in a recirculating sand filter with a design criteria of 5 gallons per square foot per day loading. Treated effluent from the sand filter is discharged to the Escondido River.

Work on the pilot project began in May 1999. The first major portion of the work was to build the pumping station for the recirculating sand filter. The pumping station was designed with a 24-hour holding time and a working volume of 3370 gallons. A pump vault is used to support two pumps which are protected with a filter. The pumps are 0.5 HP well water pumps and operated in sequence. The cycle consisted of a two minute operating period and an off cycle of four minutes. The pump cycle is controlled with an Orenco MVP-DAX1 PTRO versatile control panel. The pumping station is located on public land alongside the Escondido River. The excavation was done by backhoe and by hand and all concrete was mixed by hand on the site. Problems encountered during this phase were due to proximity of the river and starting construction during the rainy season. Water had to be constantly pumped from the excavation, which was approximately seven feet deep.

The second phase of the project was the construction of two sand filters. Each one was 60 feet by 16 feet and 3 feet 6 inches in height with a design loading of 5 gallons per square foot per day. The width of the filter was set at 16 feet to accommodate pedestrian traffic in the area (there was only about twenty feet in some locations between homes and the river). The filters were fenced to prevent vandalism and to protect the public. Wastewater is pumped from the pumping station to a diversion valve that routes the wastewater to one of four treatment zones. There were four lateral distribution lines in each zone with 1/8 inch orifices at two foot spacings. No problems were encountered in the construction of the filter walls. The difficulty in this phase was obtaining the recommended rock media size. Media specifications called for a filter media of 1.5 to 2.5 mm effective size with a uniformity coefficient of 1.5 to 2.5. The media for the number one WWTP was obtained from a near-by rock quarry that produced rock for road construction. A sieve analysis of this media indicated an effective size of 3.4 mm and a uniformity coefficient of 2.2. The media for the number two WWTP was obtained by harvesting rock from a river outside the town. A sieve analysis of this media indicated an effective size of 2.18 mm and a uniformity coefficient of 2.1. This was a much better match to the recommended size.

The Number Two Sand Filter.

The municipality had the responsibility for the third phase of the project, which was the installation of the main collection line for each block and the installation of plastic septic tanks at each home. Two sizes of septic tanks were used: 650 and 1000-liter capacity. They were constructed of PVC and manufactured in El Salvador. An effluent filter (Orenco biotube filter) was installed in the septic tanks to avoid losing solids and impacting the collection system. In the 1000-liter septic tank, there was clearance for the biotube filter at the bottom. In some cases, two homes were tied into the 1000-liter tanks. No problems have been noted in the 1000-liter installations. However, because the biotube filter in the 650-liter tank rests very close to the bottom, some filters clogged at an accelerated pace and residents would remove the filters.

The WWTPs were placed in operation in May 2000, with the official inauguration for the project held in January 2001. The responsibility for maintaining the wastewater treatment system has slowly been turned over to the municipality. It took one day of instructions to acquaint the operator hired by CHF with the basic operation of the WWTP. Duties of the operator include checking the pump stations weekly, checking the septic tanks once a month, checking the squirt height of the distribution line in the sand filters and flushing the lines on a monthly schedule. The municipality was to begin payment to the operator in September 2001. USEPA personnel will continue to monitor the progress of the WWTP and provide assistance to the municipality with the operation and maintenance requirements of the wastewater treatment system.

RESULTS

In November 2000, USEPA personnel collected influent and effluent wastewater samples to determine the performance of the WWTP. Results of the grab samples (Table 1) indicated excellent removals for BOD5, TSS, TKN, and ammonia. Ongoing monitoring of the WWTPs will be conducted by the University of San Carlos in Guatemala City, Guatemala.

Table 1.
Puerto Barrios Analytical Results
November 2000

Parameter	Plant 1 Influent	Plant 1 Effluent	Plant 2 Effluent
TSS (mg/l)	98	8.8	3.8
BOD5 (mg/l)	280	15	8.1
Nitrate-Nitrite (mg/l)	.05U	8.1	19
TKN (mg/l)	42	6.4	8.2
Total Phosphorus (mg/l)	12	7.6	6.4
Ammonia (mg/l)	30	5.1	7.1

CONCLUSIONS

When designing wastewater treatment systems, engineers should consider the appropriateness of the design for developing countries. Recirculating sand filters in combination with septic tanks are a viable solution for developing Latin American and Caribbean countries. Use of local materials and labor is important to minimize costs. Acceptance of the project by the local community adjacent to the WWTP site must also be considered. Low operation and maintenance costs and ease of operation are extremely important factors to consider.

ACKNOWLEDGMENTS

Thanks are given to Thomas Pierce and Roberto Morales from USAID who had faith in this concept. Thanks are also given to Arturo Villalobos and Nadia Gamboa with CHF for their tireless efforts in coordinating and keeping the project on track. Technical advice provided by Geoffrey Salthouse with Orenco Systems Incorporated and his fellow co-workers was crucial for the success of the project. Thanks must also go to those on the environmental committee in Puerto Barrios and to Arnulfo Lopez (committee chairman) who kept the spirit of the project alive in the town of Puerto Barrios. Al Korgi, International Coordinator for the USEPA Region 4 program, also deserves thanks for helping to maintain the commitment of the United States in improving the environment.

Photographs and Diagrams
	9 photographs	173 KiloBytes	Photo Gallery - Initial Problem
	9 pages	92 KiloBytes	Design Diagrams
	26 photographs	530 KiloBytes	Photo Gallery - Construction
	6 photographs	144 KiloBytes	Photo Gallery - Operation and Maintenance
	8 photographs	173 KiloBytes	Photo Gallery - Collection System
	3 photographs	56 KiloBytes	Photo Gallery - Monitoring

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