Sanitary Landfill System

Essential to the operation of the landfill system is an “all weather” access road with sufficient width to allow two-way traffic. The access road shall be 6 meters wide with properly compacted sub base material and coarse aggregate on top. The total length of the access road is estimated to be around 450 meters from the barangay road. A typical design of the macadam road is shown below.

Liner System

The liner system is a protective lining installed to prevent leachate from penetrating into the subsoil and contaminating the aquifer; and, subsequently, the water sources. On top of the liner system a drainage layer is placed to conduct the leachate to the embedded drainage pipes.

For Passi City, a natural liner system with clay is being considered in the design as prescribed in the IRR of RA 9003. The proposed liner system for Passi is shown below.

Seven hundred fifty (750) millimeters of compacted clay in three layers with the desired permeability of at least 10 -6 m/s are overlain with the protection layer of sand and the gravel drainage layer. The sand layer protects the clay liner, and the gravel layer conducts the leachate to the perforated drainage pipes

Storm Drainage System

The storm water collection or drainage system is an important component of a sanitary landfill system. Proper design of storm drainage system will reduce the volume of leachate requiring expensive treatment process. Since runoff water does not come in contact with solid waste, it can be discharged directly to the waterways. The drainage system also prevents flooding in the landfill cells, which will potentially increase leachate volume and compromise stability.

Storm water runoff is collected by perimeter drainage installed around the landfill cell as shown in the layout plan. Details of the drainage cross section are shown in Figure 4.4.

Leachate Management Systems

The leachate management system consists of perforated drainage pipes, storage tanks, a natural lagoon and an optional re-circulation pumping system.

The treatment system for Passi City shall consist of 2 –150 cubic meter stabilization tank and a natural lagoon system. The lagoon may also be developed into a wetland treatment system in the future. A silt basin shall be installed prior to entering the tank to exclude any solids. Final processing of the leachate shall occur in the 500 cu.m. pond which undergoes aerobic treatment process. The layout of the leachate collection and treatment system is shown below.

The pumping system is an optional feature for re-circulating the liquid back to the landfill cell. The purpose of the re-circulation of the leachate is to control and maintain the desired moisture content of the waste, to increase evaporation, and to further screen and remove waste constituents.

Leachate volume depends on the rainfall depths. Using a storm event with 25 years frequency, the estimated minimum capacity of the leachate tank would be 300 m3. This is based on rainfall data from the PAGASA Station of Iloilo City.

At the landfill cell, the perforated pipes are installed along the unit cells to drain the leachate towards the treatment system. The pipe shall be encapsulated by gravel to prevent clogging from silts and mud from the garbage. Based on the proposed layout plan, the total length of leachate pipe is estimated to be around 612 meters long.

Gas Vents

Gas wells shall be constructed to vent the landfill gases, mainly methane (CH4) and carbon dioxide (CO2). This is necessary to prevent critical methane gas concentrations within the landfill area that may lead to explosions. Collection and utilization of gas is optional for smaller SLFs with a capacity less than 500,000 tons of waste.

An option for smaller landfills like the one in Passi is to install a “dynamic” steel pipe filled with gravel. This pipe will be pulled up successively as soon as it is about to be covered by the next layer of waste, leaving behind a gravel chimney to vent the landfill. One chimney with a 50 to 60 cm diameter can serve a landfill area within a radius of approximately 25m around the vent.

MRF/ Composting Facility

In order to reach the targeted waste diversion rate, an MRF shall be constructed at the landfill site. The facility is designed to accommodate up to 1,500t/a of bio waste. The required land area for the MRF is estimated to be about 1,200 m2. Given the limited technical possibilities of the LGU, simple composting technologies shall be applied. However a certain minimum set of equipment is required to maintain the operations: a shredder (5hp), rotating screens, and a conveyor belt are recommended. A roof is needed to house the equipment and provide shelter for the processing area.

After delivery to the MRF the bio waste shall be sorted manually on a conveyer belt to remove foreign objects and fractions not suitable for the composting process. Then the bio waste shall be shredded and sieved before being mixed with 10% (Vol.) old compost and placed in windrows. The windrows are turned regularly. To ensure that the natural aeration will suffice to sustain the composting process and to enable the utilization of manual labor, windrow height shall be limited to 1.5 m. The raw compost will undergo a curing process in a roofed area. Apart from curing, the application of vermiculture technology may be considered. To remove larger particles, the final product shall then be sieved and eventually bagged for transport and sale.

The dimensions of the MRF are based on the following assumptions:

• • the bio waste is composted in windrows with passive aeration
• • windrow width is 3m; height is 1.5m
• • manual labour is used to turn the compost regularly
• • total weight loss during composting process is 50%
• • total processing time for the compost is 3 months (hot phase to curing)
• • new compost feed is inoculated with 10% (Vol.) of mature compost
• • specific weight of compost feed after shredding is 0.6t/m3
• • final product has specific weight of 0.65 t/m3

The figure below shows the general layout of the MRF/Composting Facility.

A schematic diagram of an MRF process flow is also shown in the succeeding figure. The receiving area for waste is design to accommodate at least 5 tons per day. The waste is then funneled into the belt conveyor where sorting will be done to recover re-sellable materials such as plastics, glass, can, etc. The waste then passes through the rotating screen to separate biodegradable fine materials, biodegradable materials from residual waste. The biodegradable/ compostable materials will be shredded and brought to composting area, while the residual waste will be transported to the landfill. The composted materials will undergo curing, prior to its final harvest. It is then processed to obtain a more consistent quality. After bagging and sacking, the compost will be placed in the storage area.

Utilities and Other Structures

Sanitary landfill support infrastructures shall include administration building / office, service area, water and power supply, fence, gate, and signage. Technical details of these utilities are provided in the Annexes

Administration Building

An administration building shall be constructed to house the personnel for the operation of the sanitary landfill. Apart from the necessary furniture the office shall have communications equipment, sanitary facilities, storage for filing records, first-aid kits and fire extinguisher. A small room for meetings shall be provided.

Shown below is the floor plan of the administration building and its features. A 3-D representation of the building is shown in the Annex.

Fencing

Around the landfill area, a combined interlink and concrete hollow blocks fence shall be constructed to prevent unauthorized entry of waste pickers, children and illegal settlers, and stray animals. Natural materials such as thorny shrubs may be used to support the fence integrating live fencing. A typical design of an interlink wire fence is shown in the figure below. The total length of the wire fence is around 800 meters.

Water Supply

The facility requires potable and non-potable water supply for the operation of the sanitary landfill. Potable water shall be supplied from the city in containers of 30 to 50 liters per day. Non-potable water (app. 0.5 cubic meter) may also be used from shallow wells and springs in Brgy. Aglalana which are located at a distance of about 200 m distance from the disposal facility. This water will be used for washing, cleaning and other uses.

The MRF will require about 5 cubic meters per day during the dry season to maintain the required moisture contents of the substrate. To ensure enough all year round water supply, it is recommended to establish a deep well with a submersible pump to back up the water supply from the spring and the shallow well. Typical design of well is shown in the attachment. It is also recommended to establish a rainwater collection system using the building roofs. The rainwater tank shall have capacity of 4 cubic meters to be installed in the MRF and 1cubic meters capacity to be situated in the admin office.

Power Supply

The power supply shall be tapped from the Highway, which is around 1 kilometer from the proposed site. During a meeting between the members of the technical working group and the city council, a program of works (POW) for the installation of the power lines to connect to the area and supply power to the barangay constituents and the landfill facility has been prepared

Service and Maintenance Workshop

Next to the administration building is a service station and maintenance facility. The planned area of around 250 square meters is sufficient to accommodate 3 units of heavy equipment for repair and maintenance. Only the service and maintenance portion shall be covered. A storeroom for supplies and tools with an area of 30 sq. m. shall be constructed. A floor plan for the service station/maintenance area is shown below.

Guard House, Gate and Signage

At the entrance of the sanitary landfill, a 5 meters wide steel gate shall be constructed, to allow the passing of heavy equipment. Beside the gate is a guard house for controlling and recording of incoming waste. A signage shall be posted on top painted on a steel plate. Shown below is a representation of an entrance gate.

Enhancement planting around the landfill cell

The area surrounding the actual landfill site is already partly planted with fast growing tree species. However, none of these trees are indigenous, and they do not constitute a favorable food source for the local fauna. It is recommended to plant additional indigenous fruit bearing and flowering tree species to enhance the biodiversity of the area. Recommended seedlings density is 1 per 10 sq m.

Landfill Operation and Monitoring System Manpower and Equipment for Operation

The landfill operation shall follow the guidelines stipulated in the implementing rules and regulations of the Republic Act 9003. This includes the recording of the volume of waste, tipping to the landfill cell, spreading of waste, compacting, and covering the waste with soil and/or other suitable inert materials.

Manpower / Personnel requirement

During the landfill operation, skilled and unskilled personnel are needed to ensure proper operation and compliance of the standard operating procedure. The minimum requirements to operate the facility are as follows:

• Landfill manager/administrator (1 pax)
• Secretary / Recorder (1 pax)
• Bulldozer / backhoe operator (1 pax)
• Heavy equipment technician / operator (2 pax)
• Site maintenance personnel (2 pax)
• Security personnel (1 pax)

These personnel will be provided with training and a manual of operation to ensure smooth and uninterrupted operation of the landfill site.

In addition to the personnel required in the operation of landfill, another set of personnel are needed to operate the Materials Recovery Facility. With the projected bio-waste input of 4 tons per day, the MRF would require 1 supervisor and around 6 other MRF personnel who will be involved in the processing and composting.

Equipment Requirement

To ensure compliance and efficient operation of the sanitary landfill, the following heavy equipment is needed:

• 1 unit compactor / loader
• 1 mini dump truck

The MRF shall have another set of equipment for its operation as follows:

• 1 shredder
• 1 rotating screen
• 1 conveyor belt

The conveyor belt system is used to manually screen and sort the incoming bio waste. The shredder should have at least 5 hp. If applicable the use of an electrically powered shredder may be considered. Rotating screens are designed to separate fine from larger particles.

Recording of Waste Disposal

All wastes that goes to the landfill must be recorded to monitor the volume, the source and the type of waste. The data is useful in the planning of a solid waste management program for the city. The landfill lifespan can also be projected based on the record of actual volume of disposed wastes.

Waste Compaction and Soil Covering

As soon as the waste is delivered on site, it shall be spread to a designated cell, properly compacted and covered. The exposed waste should be compacted and the site graded to slopes ranging from 2 to 4% to facilitate drainage and prevent local ponding.

Targeted minimum compaction level is 0.5 t/m3. The waste material is repeatedly spread in thin layers and compacted. A compactor or dozer shall be used to attain the desired compaction. If done properly, compaction rates of between 600 to 750 kg/cu m can be achieved, lengthening the estimated lifespan of the landfill considerably.

At the end of each operation day, thin soil layer, tarp or equivalent materials may be used to cover the fresh residual waste on site. A weekly or bimonthly covering of waste materials with soil shall be done as semi-permanent layer. The frequency can be adjusted depending on the volume of waste and the condition of the site. It is important to break the intermediate layers before new waste is placed to avoid the formation of isolated pockets and layers with low permeability. Landfill gas trapped in such pockets may lead to explosive gas concentrations and layers with low permeability interfere with the fast movement of leachate to the drainage system.

Leachate and Water Quality Monitoring

Two monitoring wells shall be constructed to establish baseline of water quality and to continuously monitor any sub-surface leaks of leachate. Locations of these wells are indicated in the proposed landfill layout plan. The water quality test should include but not be limited to: pH, E. coli, fecal coliforms, nitrate, and heavy metals. Before treated leachate is being released into the environment it has to be tested for conformity with the national standards. Recommended parameters are: pH, BOD5, COD, HCC, AOX, Heavy metals (Hg, Cd, Cr, Pb, Ni, Cu, Zn), PO4, Nitrite/Ammonium.

Gas Monitoring

Generally, landfills should undergo a monthly gas monitoring. The analysis of the landfill gas should include CH4, CO2, O2, N, F, S, benzole, vinyl chloride. However, gas monitoring is not required under the RA 9003 for smaller landfills like the one in Passi. It is recommended to have at least one portable gas measuring instrument on the site to ensure the safety of the workers.

Post-Closure Care

Once the sanitary landfill reaches the desired capacity, the closure phase shall be initiated. This phase includes two important activities, namely: a) Site rehabilitation e.g. the installation of final soil cover and vegetation cover, and b) monitoring activities.

Site improvement

Site improvement includes among others site preparation, the installation of final soil cover, the drainage control, gas management, leachate management, fencing and security.

Site Grading and Stabilization of Critical Slopes

The landfill is designed in a way to avoid critical and unstable slopes. The presented plan includes the design of the final landfill form. No slopes steeper than 1:3 are permitted; to ensure stability even by uneven landfill settling predominantly 1:5 slopes are applied. The completed landfill also features traffic ways for maintenance and surface drainage to minimize erosion.

The figure below shows the completed landfill in Passi City, i.e. with final capping, access road, perimeter drainage, etc.

Cap, top liner system

The technical specification of the final cover is stated in the Implementing Rules and Regulations of the RA 9003. Over the last waste layer a final soil cover of 0.60 m is placed. The body of waste is then sealed with a clay liner with the same specifications as the base liner, 0.75 m with 10 -6 m/s in three layers. On top of the clay liner is a drainage layer (0.2to 0.3 m) and then a vegetation layer with a min. 0.6 m.

The final cover shall act as a barrier, which will reduce the entry of water into the waste pile, preventing the new formation of secondary leachate. It shall minimize gas migration, prevent animals from getting into the underlying waste, reduce the emission of odors, and support vegetation growth.

It is recommended to use plants with a shallow, wide spread root system and high surface coverage. Grasses and smaller bushes are ideal. Trees should generally not be planted on the final layer; especially, in areas with frequent storms and on landfills with shallow topsoil.

The succeeding figure shows cross section final cap of the sanitary landfill. Below the 600 mm vegetation cover is the drainage layer and the 3-layer clay liner.

Provision of Drainage Control

Peripheral canals or ditches should be constructed around the site to divert runoff. The intention is to prevent contact of the waste pile with water thus reducing the potential for leachate generation.

Leachate Management

The leachate collection and treatment facility shall remain operational after closure and hence shall have to be managed as long as the landfill produces leachate. Before treated leachate is being released into the environment it has to be tested for conformity with national standards. Recommended parameters are: pH, BOD5, COD, HCC, AOX, heavy metals (Hg, Cd, Cr, Pb, Ni, Cu, Zn), PO4, and nitrite/ammonium.

Gas Management

The installed gas vents shall remain operational after closure. Since the Passi City landfill features only a passive gas venting system the gas vents have to be extended through the final layer (cap). The gas vent outlets should be checked regularly to ascertain the working order of the venting system. It is recommended to monitor the changes in the gas composition as an indicator of the aging process of the landfill.

Monitoring

The post-closure monitoring shall include:

• Ocular inspection to determine obvious damage to the landfill (slopes, final cover, vegetation)
• Gas monitoring as described under the previous chapter “gas management”
• Monitoring of leachate to ascertain amount and composition. The analysis of the leachte may include: pH, BOD5, COD, HCC, AOX, Heavy metals (Hg, Cd, Cr, Pb, Ni, Cu, Zn), PO4, and nitrite/ ammonium.

The monitoring activities shall be conducted last the landfill no longer constitutes possible danger to the environment and/or to the health of the people. Proper documentation and recording of the monitoring activities and tests shall be done and copies will be given to the concerned government agencies like the Environmental Management Bureau.

Post Closure Schedule

The post closure program will be initiated as soon as the landfill capacity is reached which is expected to happen towards the end of year 2017. The schedule of activities is shown in the table below.

Proposed schedule of activities during closure