Sewerage Collection and Central Treatment for El Nido Palawan

The El Nido Poblacion has a population of 5000 persons. There is now an evident adverse impact on the water quality in the bathing beach fronting this area. The LGU is keen in implementing a comprehensive sanitation solution.

El Nido, Palawan is a premier tourist destination in the Philippines. A distinct landscape of limestone cliffs and pristine white sand beaches make for a unique nature experience. The Municipality of El Nido has become keenly aware of the impact of improper waste management on its major tourist draw, the pristine physical environment. The SCOTIA project (Sustainable Coastal Tourism in Asia), a USAID funded pro-gram, is assisting the Local Government Unit in implementing a comprehensive sanitation plan for the main town proper or Poblacion area.

The Poblacion is composed of three barangays with a combined population of about 5000 persons. This is the largest concentration of the population in the Municipality. A beautiful bathing beach fronts the poblacion. This beach is already showing signs of water quality deterioration due to unmitigated impacts of improper waste management.

The proposed sanitation plan for the Poblacion is a sewerage collection system with a central treatment facility. The sewerage collection system on the average will have about 7 km of pipes ranging from 100mm to 400mm constituting the main, secondary and lateral sewer pipes. The sewage flow is seen to increase from about 1000 m3/day now to 2700 m3/day by 2022. This includes flows from the residential and commercial establishments. Four different locations were identified as candidate sites for a central wastewater treatment facility. The average capital cost for the whole facility, sewerage collection system and treatment facility would be around P 44 M. Assuming conventional treatment technology is applied, an annual operating and maintenance cost of P 2.6 to 2.9 M will be needed. Using new treatment technologies such as DEWATS and Natural Treatment Systems may lower the operating and maintenance cost. A full report on the technical details of the project is available for review.

PWRF or the Philippine Water Revolving Fund is assisting the LGU in formulating a financing strategy which will assure full cost recovery of the project.

Pangulasian Island Resort

Pangulasian Island is a day tripper's paradise, located in the middle of Bacuit Bay, El Nido. It is halfway between Lagen and Miniloc Island Resorts. Also owned by Ten Knots Development Corporation, this Island Resort once burned down completely and was rebuilt. A complete sanitation system now ensures that its operations have no negative impact on this pristine environment.

Ten Knots Development Corporation had budgeted P 1M for a sewage treatment facility for Pangulasian Island Resort (PIR). This idyllic island is a favorite day trip destination of guests from Miniloc and Lagen. It has complete banquet facilities for a full course lunch buffet with a bar. There are no guest rooms on the island. Guests normally spend the day in this island and return to the either Lagen or Miniloc. To provide for the como-fort of the guests, there are showers and toilet facilities adjoining the dining area. All the wastewater originally flowed into a bottom sealed septic tank located behind the dining pavilion. As the island became more popular for the guests, TKDC decided to provide a better sanitation system. TKDC management decided to install an engineered reed bed system as the wastewater treatment system of the island. The advantages of this system are the following; 1) lower capital cost compared to an electro mechanical treatment system 2) Aesthetically more appealing than a conventional system 3) lower operating cost (minimal electricity required) 4) simple operation and maintenance. The original septic tank was used as a pretreatment to remove solids, oils and greases. The septic tank overflow collects in a shallow sump and is pumped into a reed bed. The reed bed technical details are as follows:

The total cost for the construction of the system is P 80,000. which is less than 10% of the original budgeted cost.

The sand and gravel used for the construction and media were brought in from the mainland and not taken from the island so as to cause the least disturbance to the islands environment. Construction of the bed was done through reinforced hollow block construction with proper waterproofing. In less than three months time, the reeds had grown quite robust and tall due to the constant load of organics and surfactants. There is not reported flooding of the bed due to the layered media placement. This has prevented the bed from breeding mosquitoes.

Engineered Reed Bed Systems for GK Communities

The Engineered Reed Bed System is a simple and comprehensive way of treating septic tank overflows, ideal for small rural communities. It is a cost effective means of removing contaminants and maintaining the health and environmental quality of the community.

The Engineered Reed Bed system has been successfully demon-strated in the various coastal sites through the "Sustainable Coastal Tourism in Asia" (SCOTIA) - USAID project.

This natural treatment system uses the principle of subsurface flow rhizodegradation. When designed properly, it reduces the organic and pathogen load of a wastestream using minimal energy. Different processes occur within the root zone of the bed, both abiotic and plant assisted. The physical process of filtering is further aided by biologi-cal degradation of the organic content accelerated by plant induced aerobic pockets in the root zone.

The basic components of a reed bed are as follows;

• An impermeable bed, trough or channel. This structure may be made of reinforced concrete using hollow blocks, mono-lithic solid concrete, HDPE plastic liner, clay liners, or a combination of these.
• Inlet and outlet structures. These include the pipe distribution and collection system and clear water sump.
• Media. The media is composed mainly of gravel, sand and large rocks in gabions.
• Reeds. Phragmytes spp. is the reed which is used in reed bed systems. This is locally known as "tambo". There are three varieties of Phragmytes spp. found in the Philippines. Any of them will work in a reed bed system.

The dimensions of the bed may vary as long as it conforms with the following parameters. 1) Maximum depth is 1 m. 2) Allow for uniform-ity of flow such that short circuiting is kept to a minimum. 3) Avoid the formation of dead spots where water will not flow. 4) Bed width should not be less than 1 m to avoid formation of pools on the surface of the inlet and ponding.

Design for a 30 Household Community Assumptions:

• Water useage : 60 li/cap.day
• BOD5 : 250 ppm
• 5 persons/household
• Sealed bottom septic tank system installed (individual or shared)

The Engineered Reed Bed system will be designed to accept the overflow from the septic tank system. Ideally the reed bed system should be situated at an elevation which allows the overflow from the septic tank to run by gravity. If this is not possible then the flow is pumped through a lift station. Pump capacity will be minimal, around ½ hp to 1 hp.

Reed Bed System Dimensions