Municipal solid waste treatment complex in small towns. Case study: San Andrés de Machaca.

: The project to conceptualize the Urban Solid Waste Treatment Complex in the town of San Andrés de Machaca, has been designed to give final disposal to common solid waste and hospital waste generated in the urban area and part of the rural area, in addition to taking advantage of organic waste through the generation of compost, additionally contemplates the recovery of part of the potentially recyclable materials, which will be carried out in a recycling plant that will be located inside the complex. The proposed and requested design is intended not as a final disposal site, but rather as a complex that integrates all the units in order to take advantage of solid waste, so that in the long term the common waste cell reduces the waste it receives. and thereby increase its useful life.


Introduction
In Bolivia, the management and handling of municipal solid waste is the exclusive responsibility of the Autonomous Municipal Governments (GAM), as stated in Article 32 of the Political Constitution of the State: "The autonomous municipal governments have exclusive responsibility for urban sanitation, management and treatment of solid waste within the framework of State policy".
According to data from the Ministry of Environment and Water, in Bolivia, only 6.87%, that is, 23 of the 339 municipalities in the country, have sanitary landfills, of which only 16 are in operation; the rest (316) continue to operate in open dumps due to the lack of economic resources and trained personnel; approximately 18% are located near riverbanks, generating water pollution that has not yet been quantified. (Opinión, 2017). less and less; also that the integral and adequate management of waste is not only for large or medium-sized localities; pollution is mainly caused by the sum of several small sites due to poor or non-existent waste management.

Study Area
The Katari Basin is home to approximately 10% of the total national population, making it one of the most populated basins in the country, which in recent decades has presented a series of problems related to the management of natural resources, such as the deterioration of surface and groundwater quality. These problems, aggravated by the effects of climate change, have affected the ecosystem, livelihoods and biodiversity of Lake Titicaca.
The Bolivian sector of Lake Titicaca corresponds to the area of Lake Titicaca, and is made up of 6 provinces, of which 5 are located on the shores of Lake Titicaca and one that does not have coastline, there are several Bolivian municipalities that are relevant to carry out its sanitation San Andrés de Machaca is one of them. This has been marked by the growth of its local economies, which are dominated by agriculture, fishing, livestock, dairy farming and tourism, all of which have a significant impact on the Lake Titicaca basin. (UNESCO, 2013).
San Andrés de Machaca, is located in the Ingavi province of the La Paz Department (Figure 1), the municipality has an area of 1,575.91 km², an average annual temperature of 8°C and the town is located 116 km west of the city of La Paz, which is the capital of the country (SENAHMI, 2012).
The municipality is formed physiographically by a set of mountains and hills, so its altitude varies from 3,810 meters above sea level in the area of Lake Titicaca to 4,381 meters above sea level at Cerro Pacocahua. Most of its territory is made up of the plains of the Bolivian Altiplano; San Andrés de Machaca is an agricultural/commercial municipality.
Ordinary waste is taken to one of the municipality's official dumps located about 300 meters away.

Materials and Methods
Burning waste in the open air is an ancestral practice that reduces the infectious health risk of waste, limits the proliferation of vectors, flies and mosquitoes, as well as dogs, birds and rabbits, limits the dispersion of bags and reduces the volume of waste, which has been promoted by non-governmental organizations (NGOs) in the municipalities, particularly in the case of San Andrés de Machaca. However, this practice also has negative impacts such as air pollution and health risks due to the emission of toxic gases during burning and contamination of water sources and soil.
The burning pit is widely used by municipalities that produce little waste. The municipal backhoe digs a pit whose volume can measure between 5 and 20 m³.
In San Andres de Machaca, where the main activity is cattle ranching, less than 5% live in the capital of the municipality (total population approximately 6,100), so the project's focus should be on the rural sector. Likewise, according to the PTDI, there is a strong rural influence in the composition of municipal authorities. In this sense, rural input and contributions to the decision-making process in the municipality are important (Gobierno Autónomo Municipal de Jesús de Machaca, 2016b).
Improper waste management increases the presence of pests and animal vectors that cause disease, such as rats, pigeons, cockroaches, flies, etc.
Many micro dumps and dumps are located very close to farmland causing volatile elements to be carried by the wind and contaminating crops. In several cases animals eat plastic bags causing serious problems and even death.
The physical composition of the waste obtained in a previous characterization carried out by the Municipal Government of San Andres de Machaca is presented in Table 1 (Gobierno Autónomo Municipal de Jesús de Machaca, 2016a).
It is important to have secondary information or to carry out field work in order to have data on waste characterization. Organic matter predominates in the waste composition, followed by plastic waste and others, cited in Table 2. The data used were:  The general waste composition is shown in Table 4. Waste data are summarized in Table 5. The waste density (also called specific weight) is directly related to the physical composition of the waste, showing that the values oscillate within the common range for municipal solid waste (MSW), between 40 and 200 kg/m³. Population data, is shown in Table 6: The population of San Andres de Machaca totals 6,124 inhabitants and considering that the coverage of the sanitation service will reach 50%, the same percentage is considered for final disposal.
Generation data are summarized below:

Generation
To obtain waste generation data: Generation (ton/day) = Population (hab.) x PPC (kg/hab.-day) Sweep (ton/day) = Generation (ton/day) x 3% (Year 1 to year 5) Sweep (ton/day) = Generation (ton/day) x 2% (From year 6 onwards) Generation from years 1 to 5 is expected to be 3% of urban generation (where solid waste management is in place; rural areas are dispersed, which is why the system includes them), a percentage that drops to 2% as of year 6, since collection coverage reaches 100%, as shown in Table 7.

Utilization
For utilization, the following data come from Table 7, which are the result of urban and rural generation, and subtracting the amount of daily sweeping, we have the generation data by type of waste in Table 8.  To obtain the results of Table 10, the household waste data (1.08 ton/day), recorded in Table 8, must be multiplied with the percentage of recyclable and organic waste recorded in Table 9 (31.4 and 26.1%, respectively), and also the remaining percentage (42.4%) that is garbage; in the same way for the projection of year 20, in this way the amount in (ton/day) according to typology will be obtained. With the results obtained in Table 10 and according to the proposed composting goals, the amount of waste to be composted in tons/day is shown in Table 11. With the results obtained in Table 10 and according to the recycling goals set, we can have the amount of waste to be recycled in ton/day, as shown in Table 12.

Proposed goals
It is necessary to set goals that define a reasonable growth in the use of organic waste and recyclable waste, such goals are given by the conditions that the municipal government has at the moment, ideally if there were data on recycling in some neighborhoods of the municipality, it would help to be able to project these data.
With these growth rates, the target is met over the life of the project.
Growth rate Composting 5.0% per year Recycling Growth Rate 8.0% annual Having calculated the amount of waste to be used, the % for composting and recycling should be obtained for each, with respect to the generation (recorded in Table 7), the amount of waste to be composted is divided by the total generation, in the same way for the waste to be recycled, the results in Table 13.

Waste flow within the complex
To complete the waste flow, we must include the percentage of rejection, the percentage that is estimated, but that is given by the experiences of utilization, both for recycling and composting is 5%, percentage to the amount of ton/day of both (recycling and composting), so that we finally obtain the amount that would go to the landfill.
Composting rejection = Amount of waste to be composted x Composting scrap material (5%) Recycling rejection = Amount of waste to be composted x Recycling scrap material (5%)

Common waste cell
With the values obtained in Table 14, the waste projection is made for the common waste cell.  Loose density kg/m³ 0.25ton/m³ Compacted density kg/m³ 0.45ton/m³ Stabilized density kg/m³ 0.55ton/m³ Covering material 15%

Leachate
Leachate is calculated as follows: where: Q is the average leachate flow rate in L/seg; P is the average annual precipitation; A is the surface area of the landfill cells in m²; t is the number of seconds in a year; and k is the coefficient that depends on the degree of compaction of the garbage (0.35-0.50). A capacity of 71.89 m³, stores leachate 895 L/day, the tank has a capacity of 12 days, and then goes to the evaporation pool, with a capacity for 90 days (3 months). The solar radiation values are high since the location is in the altiplano; Bolivia is one of the countries that receives the most solar radiation in the world. 66% of Bolivia has one of the highest levels of solar intensity on the planet, the highest annual average daily solar radiation is present in the altiplano (Solón, 2017) Among the main climatic parameters that affect evapotranspiration are radiation, air temperature, atmospheric humidity and wind speed (ALLEN, 1994)

Compost
The composting area is a site with a fence made of callapos, its dimensions 5.0 The volumetric calculations are detailed in Table 17 below. The Table 18 details the dimensions of the compost module. One module covers the capacity of 4 days of organic waste generation.

Recycling
The sorting area for recycling will be a shed, where recycling techniques can be implemented as this practice grows in the municipality. The Table 19 details the dimensions of the selection area. The volume calculations are detailed in Table 20, considering a density of 900 kg/m³, the monthly capacity is 5.5 m³ (according to the proposed goals).

Supply -Demand Balance
From the comparison of demand and supply, the future deficit was established if the current conditions in the municipality are maintained.
The projection of the deficit between current supply and demand is shown graphically in Figure 4, which shows the lack of a final disposal site for solid waste. The generation of solid waste in the municipality will increase 37% by the year 2040, assuming that per capita production remains the same, and it is projected that the percentage of collection coverage will decrease from 100% to 77% in the same of time. Taking into account the above, it is evident that there is a deficit between the growing demand and the current supply in the municipality in terms of waste management.
As shown in the Figure 4, the final disposal site in the municipality of San Andrés de Machaca should have a capacity of approximately 1,042 tons in order to store the total amount of waste generated in the municipality. The landfill will dispose of an average of 45 tons of waste per year. It is estimated that approximately 83 tons of waste will be used, according to the proposed use percentages. The projection of the deficit between current supply and demand is shown graphically in the Figure 5. As can be seen in the graph, the lack of a final disposal site for solid waste is evident. The generation of solid waste in the municipality will increase by 37% until 2040, assuming that per capita production remains the same, and it is projected that the percentage of collection coverage will decrease from 100% to 77% in that period of time.
Taking into account the above, it is evident that there is a deficit between the growing demand and the current supply of the municipality in terms of waste management.

Results and discussion
According to the calculations performed, the following results are obtained, for the 20 years projection: The Flow Diagram of the Complex is shown in the Illustration of Figure 6, the values that are presented are those projected at 20 years, it is important to highlight the reduction of waste that enters the WTC, which starts with 800 kg/day and at year 20, reduces to 260 kg/day, thanks to the use.
The solid waste treatment and disposal complex consists of a common waste cell, an emergency cell and a safety cell (bioinfectious), each of which includes adaptation works such as excavations, landfills, roads, a leachate drainage system, chimneys for gas management and rainwater management ditches.
The San Andres de Machaca Waste Disposal and Treatment Complex (WTC) includes eight key processes: • Waste registration and inspection; • Organic waste composting; • Recycling in the selection area • Final disposal of household solid waste and assimilable waste in a common waste cell; • Final disposal of household solid waste and similar waste in an emergency cell • Final disposal of hospital waste in a safety cell; • Hazardous waste storage • Leachate storage • Leachate treatment (evaporation pool) The main activities to be developed within the Complex are as follows: • Reception, inspection and registration of waste entering the center.
• Waste discharge by type and handling.
• Final disposal of household and similar solid waste in a common waste cell.
•  The useful life of the complex is 20 years, a period for which all facilities have been designed. Both the design of the Complex and all activities or works related to its construction, operation and closure have been carried out in accordance with current Bolivian regulations (Agua, 2012).
The following is a detail of the surface areas of the aforementioned areas The Figure 8 shows the virtual model of WTC San Andrés de Machaca The required area data for the first year of operation are as follows: The budget was developed, starting with the design, metric computations, unit price analysis and finally the total budget.

Conclusions
The Waste Treatment Complex -WTC, has a cost of US$350,000.00, with a useful life of 20 years.
The solid waste treatment and disposal complex consists of a common waste cell, an emergency cell and a safety cell (bioinfectious), each of which includes adaptation works such as excavations, landfills, roads, a leachate drainage system, chimneys for gas management and rainwater management ditches.
The proposed design is not intended as a final disposal site, but rather as a complex that integrates all the units in order to make the best use of solid waste, so that in the long term the common waste cell will reduce the waste it receives and thus increase its useful life.
We always focus our attention on medium and large localities, leaving aside the small ones, which are usually the majority, therefore the proposed study aims to solve these small localities, in a comprehensive manner, with an adequate budget considering the projection for 20 years.
Likewise, these localities are the ones that occupy sites close to water sources, contaminating in a great way a whole region.
The volumetric requirements for the design of the landfill were estimated for 20 years, using the total annual and accumulated volumes of both solid waste and cover material, using the waste generation projection and the volumetric weights of the confined waste.
It is important to mention that the projection of waste to be disposed of in the Solid Waste Complex was made considering that the municipality will adopt the utilization programs proposed in this study, and without taking into account volume losses due to decomposition of organic matter and loss of natural moisture.
The project to conceptualize the Urban Solid Waste Treatment Complex for the town of San Andrés de Machaca has been designed to provide final disposal of urban solid waste and hospital waste generated in the urban area and part of the rural area, as well as to take advantage of organic waste through the generation of compost; it also contemplates the recovery of part of the potentially recyclable materials, in which a recycling plant will be built.