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International Journal of Advanced Science and Technology Vol. 29, No. 7, (2020), pp. 2375-2382

Geochemical Evaluation of Contaminated Soil for Stabilisation Using Microbiologically Induced Calcite Precipitation Method

[1]Jodin Makinda, [2]Khairul Anuar Kassim, [2]Kamarudin Ahmad, [2]Abubakar Sadiq Muhammed, [2]Muttaqa Uba Zango [1],[2] School of Civil Engineering, Faculty of Engineering, Universiti Teknologi Malaysia, 81310, Skudai, Johor Malaysia [1] Faculty of Engineering, Universiti Malaysia Sabah, 84000, Kota Kinabalu Sabah, Malaysia

Abstract Abandoned mines contaminated with heavy metal wastes pose health risk and environmental hazard. Common methods in managing these wastes include pond storage, dry sacking, underground and ocean disposal and phytho-stabilisation but these does not address the associated risks regarding migration of contaminated liquid or when the soil structure is compromised during natural disaster such as earthquake. Due to these limitations, microbiologically induced calcite precipitation method (MICP) is an exciting alternative as it is sustainable and environmentally friendly. This research evaluates mine waste obtained from two sites; Mamut and Lohan Dam, both located at earthquake-prone Ranau Sabah, Malaysia, in term of their physical, mineralogy and morphological characteristics for stabilisation using MICP. Physically, mining wastes from Mamut are of well graded soil with sand (53.9%) and gravel (43.5%), classified as SW (USCS) and A-1-a (AASHTO). Meanwhile, waste from Lohan Dam are of sand (49.9%) and gravel (10.1%), classified as SM (USCS) and A-4 (AASHTO). Constant head test of the soils from the sites showed results of 3.607 x 10-1 and 3.407 x 10-2 cm/s respectively indicate high permeability. Mineralogy assessment using inductively coupled plasma atomic emission spectroscopy (ICP-OES) showed high level of iron (Fe) with 528.08 and 2931.38 mg/L respectively. Other heavy metals detected include copper (Cu), 24.39 and 4.33 mg/L, lead (Pb), 2.53 and 0.53 mg/L, manganese (Mn), 5.71 and 3.64 mg/L and arsenic (As), 0.71 and 0.31 mg/L; some higher than Malaysia’s Ministry of Health and United Nations’ Food and Agricultural approved standards. Morphological observation of the size, shape and soil texture under scanning electromagnetic (SEM) further indicate the necessity and suitability of both sites for stabilisation using MICP.

Index Terms—Contaminated Soil, Microbiologically Induced Calcite Precipitation, Mine Waste, Soil Stabilization

I. BACKGROUND, MOTIVATION, OBJECTIVES In 1970s, Malaysia was one of the world’s leading countries in minerals production of tin, copper, bauxite, gold and ilmenite. Indeed, mining was one of the major contributor to the GDP, producing almost 31% of the world tin output in 1979 but the production fell by 90% over the last 15 year [1]. Due to the exhaustion of mineral deposits, low prices and high operating costs, many of the mines are now abandoned include sites in Bukit Botol, Bukit Ibam, Panching, Sg Lembing, Kota Gelanggi, Padang Piol and Kg Awah in Pahang [2] and Mamut in Sabah [3]. Heavy metal wastes from abandoned mines are known to pose health risk to the surrounding settlement and potential hazard to the environment. For example, Mamut cooper mine which was in operation from 1975 to 1999 generated about 350 Mt of waste, of which 250 Mt are rocks and overburden materials and over 100 Mt of tailings. The wastes from this mine were dumped at various sites near the areas [4]. Compared to other developing countries, Malaysia has not inherited such a serious legacy of contaminated land and most of the identified possible sources of contaminations come from motor

workshops, petrol stations, fuel depots, railway yards, landfills, industrial sites and ex-mining land. Probably due to this, little works have been carried out in identifying and stabilizing contaminated lands. Currently, most methods in management of wastes include pond storage, dry sacking, underground disposal, ocean disposal and phytho-stabilisation does not address the associated risks regarding migration of contaminated liquid or when the soil structure is compromised during natural disaster such as earthquake. Other approaches on remediation of contaminated mine waste are by using stabilizers to bind the waste particles thus immobilizing the contaminants and minimizing leaching into the surrounding environment. Among the previous studies include immobilization of sulfates and heavy metals in gold mine tailings by sodium silicate and hydrated lime [5], treatment of acid mine drainage using limestone and activated sludge [6], stabilization of arsenic with basic oxygen furnace [7], phosphate treatment for the remediation of contaminated mine waste [8], application of coal combustion by-products in mine site rehabilitation [9], use of clay liners, whose essential material is bentonite to decrease the hydraulic conductivity of landfills [10], Portland cement application to control acid mine drainage generation from waste rocks [11], use of fly ash for backfilling abandoned room and pillar mines [12], use of Si-rich substances to regulate the mobility of pollutants in soil and water and enhance the plant resistance to its toxicity [13] and use of serpentinite and concrete waste to raise pH level and removing metal ions concentrations from acid metal drainage [14]. However, question is still arising on the use of these industrial based by-products as they alter the pH of groundwater and thus may cause serious environmental problems and contribute to the ecosystem disturbance [15]. Since MICP is considered as newer, more inventive and environmentally sustainable compared to the other methods, a wider application of this technique in geotechnical engineering should be explored. MICP is a biologically driven calcium carbonate (calcite or CaCO3) precipitation technology, either controlled or induced. When it is biologically controlled, organism independently synthesizes minerals unique to the species regardless of the environmental conditions while induced mechanism produces CaCO3 somewhat dependent of environmental condition[16]. The factors affecting the effectiveness of the treatment include type of bacteria, treatment method, temperature, bacteria concentration, pH, degree of saturation and most importantly the geochemical properties of soil [17]. This research reports the preliminary geochemical evaluation made on mine wastes collected from several points near abandoned Mamut Copper Mine, Ranau, Sabah, Malaysia shown in Figure 1. While MICP is gaining popularity to treat problematic soil such as liquefaction, internal erosion, settlement and frost damages, its potential in treating contaminated soil, particularly of mine waste is still not explored fully. The research is motivated by the increase in land contamination in Malaysia and particularly in the study area, some infrastructures were reportedly damaged due to a 6.0 magnitude earthquake on 5th June 2015, causing ground failure and rising fear of wall of open pit in abandoned mines breaking, causing water to flow out to the water resources utilised by nearby residents [18].

II. MATERIALS AND METHODS

A. Materials Sampling was conducted near the abandoned Mamut mine and Lohan Dam about 8 Km away where the tailings were piped, routed and deposited. The GPS coordinates for both locations are as shown in Table 1.

Table 1: Sampling Locations

Sample Location Mamut 6°1′ 37.7″ N, 116°39′ 21.0″E

Lohan Dam 6° 0' 45.936'' N, 116° 44' 20.004'' E

The samples were collected at depth of 0.5 m to 3.0 m of the soil profile and submitted to Geotechnical Laboratory, Universiti Malaysia Sabah for geotechnical tests.

Figure 1: Location of Study Area [19]

B. Geotechnical Test The geotechnical properties determined were their natural moisture content, sieving analysis, Atterberg limits, pH, specific gravity and organic matter. Dry and wet sieving method was used to determine the particle size distribution of coarser and finer soil respectively. pH was measured by pH meter and specific gravity, permeability and organic matter were measured according to British Standard. Following the tests, the mine wastes were classified based on their particle size, particle distribution and texture using two major classification systems; AASHTO and USCS. All laboratory tests were performed at according to BS 1377: Part 2: 1990. C. Mineralogy Test The air dried and powdered sample were then made into pressure, digested and analysed using inductively coupled plasma optical emission spectrophotometer (ICP-OES) to determine the concentration of heavy metals and major elements. All mineralogy and morphology tests were performed University Industry Research Laboratory, Universiti Teknologi Malaysia. D. Morphology Assessment A scanning electron microscope (SEM) with a maximum magnification of about 1000x were used to generate high-resolution images and precisely measures very small features on the surface of the soil sample.

III. RESULTS, DISCUSSION AND CONCLUSION

A. Geotechnical Properties Table 2 and Figure 2 show the geotechnical properties and gradation curve aof both Mamut and Lohan Dam soil. Based on the particle size distribution, Mamut contains 97.4% coarse grain compared to 60.0% for Lohan Dam.

Table 2: Properties of Mine Waste Properties Mamut Lohan Dam

Natural Moisture 11.04 26.68 Content (%) Grain Size Distributions 97.4 60.0 Coarse Grain (%) 43.5 10.1 Gravel (%) 53.9 49.9 Sand (%) 2.6 40.0 Fine Grain (%) Atterberg limits - 27.0 Liquid Limit (%) - 23.5 Plastic Limit (%) - 3.5 Plasticity Index (%) Soil Classification USCS SW SM AASHTO A-1-a A-4 pH 4.53 6.18 Specific Gravity 2.75 2.66 -1 Permeability, (cm/s) 3.607 x 10 `3.407 x -2 Organic Matter, (%) 0.15 10 0.77

Subsequent consistency test on the fine-grain particles of Lohan Dam sample indicate low plasticity, with PL of 3.5%. Based on these, Mamut soil is best classified as well-graded sand (SW) and Lohan Dam is silty-soil (SM) under USCS and A-1-a and A-4 respectively, under AASHTO. The dominant percentage of coarser particles also resulting higher permeability and specific gravity for both soils. Under MICP treatment, microbes are expected to move freely within the voids of the soil aggregates, their movements are restricted by the narrow pore sizes formed by fine grained soils. Bacteria sizes range between 0.5 mm and 3 mm, as such they are not likely to pass through pore spaces smaller than 0.4 mm.

Figure 2: Gradation Curve of Mamut and Lohan Dam Soil

Table 3: Mineralogy of Mamut and Lohan Dam Mine Waste

Heavy Metal Mamut (mg/L) Lohan Dam (mg/L) Elements Point 1 Point 2 Point 3 Average Point 1 Point Point Average 2 3

Arsenic, As 0.696 0.717 0.724 0.712 0.315 0.319 0.323 0.319 Cadmium, Cd -0.033 -0.033 -0.033 -0.033 -0.052 -0.051 -0.051 -0.051 Cobalt, Co 0.070 0.071 0.071 0.071 -0.026 -0.025 -0.024 -0.025 Chromium, Cr 2.116 2.179 2.148 2.148 0.578 0.588 0.591 0.586 Copper, Cp 24.669 24.617 24.104 24.396 4.287 4.327 4.396 4.337 Iron, Fe 529.299 529.909 525.054 528.087 2926.2 2951.1 2916.9 2931.4 Manganese, 5.616 5.813 5.720 5.717 3.601 3.627 3.698 3.642 Mn 1.612 1.186 1.178 1.175 0.372 0.378 0.378 0.376 Nickel, Ni 2.554 2.538 2.512 2.534 0.508 0.554 0.541 0.535 Lead, Pb 2.021 2.072 2.048 2.047 0.546 0.560 0.560 0.555 Zinc, Zn

Meanwhile, in coarse-grained soils like both samples, bacteria can freely move between the soil mineral particles and may stick on the mineral surfaces and form micro colonies or biofilms [17]. On the other hand, low pH indicates the acidic nature of rocks and minerals in large volume. As such, rehabilitation and treatment using neutralization method with lime is considered costly [4]. It is also observed that both soils contain low organic matter, an indicative of lack of vegetative growth which is a challenge for phytho-stabilisation method [20].

B. Mineralogy The level of heavy metals in soil samples collected from Mamut and Lohan Dam are shown in Table 3. Samples from Mamut were found to have higher average contents than Lohan Dam in all heavy metal elements analyzed except iron, Fe. In general, the heavy metal levels in Mamut such as As, Cd, Co, Cr, Cp, Mn, Ni, Pb and Zn were 2-5 times higher than Lohan Dam. This is probably because the waste soil from Lohan Dam were originated, routed and deposited from Mamut. When compared to the standard of Department of Environmental Malaysia (DOE) and Food and Agriculture Organization of the United Nations (FOA), the concentration (in mg/L) of As 0.712 and 0.319, Co (0.071, -0.025), Cp (24.396, 4.337) and Ni (1.175, 0.376) are beyond the safe levels. As such, both soils are good candidates for MICP treatment. However, bioremediation of contaminated sites will be more effective if suitable bacteria that stable in high concentrations of these heavy metal elements is used [21]. Bacillus pasteurii or Sporosarcina pasteurii are the most preferred bacteria reported in the literature for the MICP process because of their ability to produce high amount of precipitates within a short period of time due to their high urease activity. The bacteria are native to the earth, hence they may not likely cause any environmental hazard in future.

Morphology The SEM analysis of Mamut and Lohan Dam soils are shown in Figure 3 (a,b) and Figure 4 (a, b) respectively. They appear to be composed of powdered and hardened particles with dark brown colour. By comparison under x100, Mamut soil contains higher amount of larger particles than Lohan Dam. Under x1000, the particles in both samples are mostly well rounded and spherical in shapes but some irregular-shaped particles are also observed.

Figure 3 (a) Mamut (x100)

Figure 3 (b) Mamut (x1000)

Figure 4 (a) Lohan Dam (x100)

Figure 4 (b) Lohan Dam (x1000)

Their surfaces appear to be very smooth with no agglomeration between particles. This may indicate that without treatment, the strength value of mine waste is low due to the low bonding between the loose grain structure. Previous study found that particle size and shape notably influence the mechanical response, where an increase of 35%, 50%, and more than 100% in shear strength for round coarse, angular coarse and round fine particles respectively, on sand treated with MICP [22].

IV. CONCLUSION

From the preliminary study, following conclusions can be made; i. Both Mamut and Lohan Dam mine wastes are predominantly coarse grain soil of low plasticity, high specific gravity and high permeability making them susceptible to land contamination. ii. Both soils are acidic in nature and their low organic content may indicate that stabilisition by neutralization and phytho-stabilisation methods will be costly and not conducive. iii. Both soils contain high level of heavy metals beyond the safety level of Department of Environmental Malaysia (DOE) and Food and Agriculture Organization of the United Nations (FOA) making them good candidates for MICP stabilisation.

V. ACKNOWLEDGEMENT

This work was supported by the Ministry of Education Malaysia’s Fundamental Research Grant Scheme [R. J130000.7851.5F256] and the High Impact Research Grant [Q. J130000.2451.04G57].

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