Results and Discussion

Frequency and spatial patterns of open dumps in relation to urban demography

A total of 452 unauthorized dumps spatial pattern analysis was conducted to identify regions dominated by open dumps. This effort also helped in finding undiscovered dumps while understanding the propensity for the occurrence or formation of dumps. The population density and occurrence of open unauthorized dumps were correlated. The core city area has a higher population density. Core areas with a population den- sity of 5,000-10,000 persons/km2 was found to have open dump sites generally smaller in size and temporary in nature (Chanakya et al., 2015). Waste composition found at these core city dump sites, it was found that the organic fraction was quite high shows very recent origin of 1-3 days mainly due to a lack of a regular waste collection and removal sys- tem. These ephemeral dump sites are cleared at this above frequency of 2-3 days but recur immediately after their being cleared. These need to be overcome by adopting a higher degree of coordination between primary collection and trans- portation system. A larger number of dump sites were found outside of the core area (outskirts and peripheral areas) wherein population densities ranged between 100 and 1000 persons/km2 (Figure 4). This is comparable to the earlier study conducted in Japan (Tasaki et al., 2007). Areas with a lower population density tend to have greater number of open dump sites and is evident from the higher level of occurrenc- es of dumps in localities more than 7 km away from the city centre (Figure 2). The area within 10 to 20 km away from the city centre had higher number (80%) of dump sites. This is attributed to availability of common lands, abandoned agri- cultural lands apart from sites that have lower visibility and proximity. This indicates that as the distance from the city centre increases, the number of open dumps tends to increase. Large trucks are generally responsible for the transport of MSW in quantities ranging from 5-8 t/truck load and their disposal to these specific dump sites. The specific heaps found at these locations bear out that dumper trucks or vehi- cles of similar capacity are predominantly responsible for these unauthorized dump sites. At these locations it is not discernible if handcarts and auto tippers carrying out primary collection at the outer area also dump at their daily collection at such dump sites. This study and related observations did not implicate them in a significant way. Unauthorized dumps by these large trucks thus require road access round the year else, it would be impossible for large garbage trucks to dump their MSW load at locations other than on the roadsides. Fur- ther, continuous visits on unprepared soil will also create difficulties for trucks to access these sites on a long-term ba- sis. Earlier study indicated that these trucks generally prefer main arterial roads during the main part of the journey out of the city and only when they are out of the denser part of the city these trucks tend to carry out illegal dumping (Ra- jabapaiah, 1988). Assuming this practice still continues, an attempt is made to evolve a relationship between distance between a major road and the chosen dumps.

The main road network (National Highways, State High- ways and Major District Roads; NH, SH and MDR, respec- tively) farther away from the city centre had more number of dumps. This is similar to earlier study findings (Rajabapaiah, 1988). However, now there is a clear region or band wherein most of the dumping occurs. Generally, areas at a distance of more than 1500 m from the main road network had higher number of dumps. This phenomenon has been observed in areas located inside the core city area, outskirts and also, along the peripheral areas (TIDE, 2000). Visual observations on the size and shape of heaps indicated that this practice of dumping was carried out predominantly by larger waste col- lection trucks rather than by local residents or by smaller ve- hicles used in the primary collection process. It is obvious that these heavy trucks require a pliable road all round the year which can bear the weight of such trucks (10-15 Mg) and hence, they can reach the dump site they usually dump wastes in. This significantly restricts the creation of a large number of open dumps at distances more than 1500 m away from the main road network of the city.

Waste composition at dumps

Out of the total number of locations covered in survey, 44% had a dominant quantity of construction and demolition wastes. The dominant component of wastes recorded in open dumps was construction debris, followed by organic wastes and plastic wastes based on the area of spread and volume of waste present. Organic and plastic wastes occur at 25% and 22% of the dumps. For dumps located in the core area, as opposed to the peripheral area discussed above, the largest number of dumps had organic wastes (48%), followed by plastic (26%) and construction debris (17%) as dominant components. The major contribution outside the core area was from construction debris as observed in earlier study (Chanakya et al., 2015). This indicated that the dumps studied were in their last phase of utilization, namely, the stage when the predominant MSW dumped was slowly being covered up by the next stage of utilization of these dumps by dumping C&D wastes (Chanakya et al., 2015).

Waste composition at 28 selected dump locations

Figure 5 depicts the segregated components at 28 chosen dumpsites. The overall waste composition was found to be predominantly 41.3% of construction debris followed by 28.9% of organic waste and other fractions constituted the remaining. The organic waste fraction was less than the gen- erated waste in low-density, medium-density and high- density population areas (Speier et al., 2018). It shows that these sites are at the last phase of waste dumping where C&D waste provides a good cover or capping to the wastes dumped till this period and second, the presence of C&D wastes leaves the sites clear for immediate use for realty to commer- cialize (Chanakya et al., 2015).

Analysis of samples collected at dump site locations shows that moisture content ranges from 1 to 4%, which is extremely low compared to fresh generated waste (Sharma et al., 2019). Total volatile solids in samples were found to vary from 24 to 93%, while the total carbon content varied from 8 to 49%. The hydrogen and nitrogen content varied from 1 to 7% and 0.4 to 3%, respectively. These variations in samples indicate variability in degraded organic fraction of municipal solid waste as these sites are continuously used from 3-4 years as waste dump sites. The organic wastes constantly degrade, thereby increasing the relative percentage of inert components such as plastics and construction debris. Con- struction debris and demolition wastes are major components of open dump sites that remain visible for a long period as the organic and recyclable fractions are gradually lost.

Density of wastes accumulated in open dumps

FIGURE 5

Waste composition of dump site locations

Wastes accumulated in open dumps consist of construc-

tion debris, organic wastes, plastic wastes, old wastes, other substances (viz. paper, cloth, glass, leather, burnt wastes) and rejects from recycling units. Measured densities were 1.01 Mg/m3 (for construction debris), 0.11 (of organic wastes), 0.05 (of plastic wastes), 0.04 (of old wastes), 0.09 (of other substances) and 0.12 Mg/m3 (of recycling rejects), respective- ly. Other wastes include burnt waste which are extremely fluffy and amenable to secondary dispersal by wind and rainwater. Organic wastes at this stage is partially dry and lighter than fresh organic waste when collected at the source. Most of the organic matter that has degraded or dried with time has a low density (0.04 Mg/m3) and is categorized as "old wastes.”

Waste spread area at open dump sites

Waste spread area was estimated at 268 of these locations using GPS to determine area of spread. The total area of spread was 120212 m2. The land area of open dumps found in the core area and outside the core area were 2941.45 m2 and 117270.5 m2 (outer areas 48509.96 m2 and peripheral areas 68760.58 m2), which is equivalent to 0.02% of total area of Bangalore. The area of waste spread increased from the core to the periphery of the city as the number of dump sites also increased from inside to the outskirts of the city.

Height of open dumps

The average height of dumps was 0.69 m. The dump height varied from 0.24 to 1.09 m in the inner core areas with an average dump height of 0.56 m. The height of the dumps varied from 0.10 to 7.11 m in outside the core area depending upon surrounding area and dumpsite visibility. The average height of dump in outside the core area is 0.75 m indicating greater accumulation of waste in the peripheral regions in addition to having a longer residence time.

Quantity of wastes in open dumps

Average waste volume accumulated in 268 dump sites located inside the core area and outside the core area and pe- ripheral area of the city are 1989 and 102660 m3, respective- ly. The waste quantity measured is 63652 Mg with a share of 0.5% from core area and rest 99.5% from outside the core area (42.7% from outer areas and 56.7% from peripheral are- as; Table 1). Table 1 shows that the waste quantity varied for various waste categories. The quantity of waste dumped was highest in the peripheral area of the city.

The results of this study showed that large open dumps are predominant at locations farther than 1500 m away from the main roads with low population densities (from 100 to 1000 persons/km2) and at a distance of greater than 10 km from the City Centre. The proximate analysis of samples col- lected at dump site locations confirms the variability in or- ganic components of municipal solid waste dumped in dump sites. The main component of these dumps nearer the time of its maturity is construction debris. Considering the average height of 268 estimated open dump sites, total 213310 Mg of waste is dumped in 452 locations. It is equivalent to 17% of annual MSW generated from Bangalore city and therefore is indicative of the need to find mechanisms that obviate or overcome the propensity to indiscreet dumping. This study shows a method to quantity of waste dumped in open disposal sites as well as validate this data in multiple ways to achieve a higher degree of accuracy and may be extended to other Indian /developing country situation.