WMR0010.1177/0734242X15580193Waste Management & ResearchLiu et al.

Short Communication

Study on detecting leachate leakage of municipal solid waste landfill site

Waste Management & Research 1­–5 © The Author(s) 2015 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0734242X15580193 wmr.sagepub.com

Jiangang Liu, Xianxian Cao, Yingbo Ai, Dongdong Zhou and Qiting Han

Abstract The article studies the detection of the leakage passage of leachate in a waste landfill dam. The leachate of waste landfill has its own features, like high conductivity, high chroma and an increasing temperature, also, the horizontal flow velocity of groundwater on the leakage site increases. This article proposes a comprehensive tracing method to identify the leakage site of an impermeable membrane by using these features. This method has been applied to determine two leakage sites of the Yahu municipal solid waste landfill site in Pingshan District, Shenzhen, China, which shows that there are two leachate leakage passages in the waste landfill dam A between NZK-2 and NZK-3, and between NZK-6 and NZK-7. Keywords Leachate of landfill, conductivity, chroma, groundwater temperature, horizontal flow velocity

Introduction The leachate of waste landfill is a kind of wastewater, it has a mutable nature, is complex, has a high content of components and is hard to be degraded and be disposed. The situation that groundwater polluted by leachate in various degree exists in many Chinese waste landfills sites (Dong et al., 2014; Ning and Chen, 2012; Zhu et al., 2005), the reason is mainly that the impermeable membrane cannot always maintain a perfect anti-seepage function during construction and operation. Therefore, determining the leakage site of an impermeable membrane and reinforcing the anti-seepage structure is very important to prevent leachate further getting into the groundwater system. However, there are few articles about detecting the leakage site of impermeable membranes at home and abroad (Guo et al., 2012; Wang et al., 2002), only some articles are about monitoring and evaluating the leachate of waste landfill and groundwater (Jiang, 2008; Zhang et al., 2008). This article studies the method for detecting the leakage passage of leachate using a comprehensive tracer.

can be one tracer dimensionality to judge that the leachate has leaked or not.

Leachate temperature Because of the various complex components and the accumulation of change in the environment and stress, there will be a series of biochemical reactions that give out a lot of heat inside the waste landfill, waste landfill will become a heat source body, and the temperature increases by 11 °C~25.6 °C (Liu and Huang, 2010). There are few reports about the temperature of waste landfill (Yang et al., 2008; Zhang et al., 2007). The temperature of leachate inside the waste landfill is generally higher than that of shallow groundwater at the same elevation surface around the waste landfill site, so the leachate temperature could be used to determine the leakage site as a tracer dimensionality.

Leachate chroma (or colour) Tracer elements and their action at the waste landfill site Leachate conductivity Conductivity depends primarily on ion composition and content in the water. The leachate contains inorganic components and organic components, both of which can form ions and then have conductivity. Because of the high content of components in the leachate, the conductivity of the leachate is very high, even up to 50,000 μS cm−1. Leachate conductivity is much higher than the conductivities of groundwater, river water and meteoric water around the waste landfill site, therefore, leachate conductivity

Chroma is not only the reflection of the leachate components, but also the symbol of waste ‘age’. At the time of waste filling, the leachate is black, having good biodegradability and being easily disposed; with the waste filling time expanding, the leachate becomes brown, the biodegradability becomes bad the serious School of Earth Science and Engineering, Hohai University, Nanjing, China Corresponding author: Jiangang Liu, School of Earth Science and Engineering, Hohai University, No.1 Xikang Road, Nanjing 210098, China. Email: [email protected]

Downloaded from wmr.sagepub.com at RICE UNIV on May 19, 2015


Waste Management & Research

Figure 1.  Diagram of plane distribution of the new and old reservoirs and drainage system.

disproportion of C:N:P appears. In other words, leachate chroma could be used to recognise initial and old leachate, intuitively.

Horizontal flow velocity of groundwater Once some parts of the impermeable membrane leak, the flow field of the leachate at the leakage site and of the groundwater under the impermeable membrane will change, and the horizontal flow velocity will increase. Therefore, according to the horizontal flow velocity, the leakage site of leachate can be recognised. The horizontal flow velocity can be gained in a single borehole, and the seepage velocity could be calculated, as:

Vf =

π (r12 − r02 ) C0 − Cb ln . (1) 2α r1t Ct − Cb

where V f is the seepage velocity (m d−1), α is the distortion correction coefficient of flow field (dimensionless), r0 is the radius of the probe (m), r1 is the inner radius of filtering tube (m), C0 is the tracer concentration at the time of t=0 (ppb), Ct is the tracer concentration at the time of t (ppb), Cb is the tracer background concentration (ppb), and t is the time of tracer concentration changing from C0 to Ct.

Overview of Yahu municipal solid waste landfill site and methodology Yahu municipal solid waste landfill site in Pingshan District, Shenzhen, China, is an annular valley type landfill site, which

consists of an old waste cell, old waste dam, new waste reservoir, new waste dam, anti-seepage structure and leachate drainage system, groundwater drainage system, etc.; the plane distribution is shown in Figure 1. The anti-seepage cushion structure of the new reservoir is shown in Figure 2, while the old waste cell does not have groundwater drainage pipe. Currently, the new waste reservoir is not in operation, while the old one has been used for 3 years, and the height of the waste has reached to the elevation of dam A crest. Shortly after the waste landfill site was in operation, some brown leachate was found at the outfall of groundwater drainage system. The new waste reservoir has not been put into use, therefore the leachate appears to be coming from the old waste cell. In order to find the leakage site of the anti-seepage cushion of the old waste cell, ten exploration holes were arranged in dam A (NZK-1~NZK-10 in Figure 1), the depth of all the holes were 20 m, NZK-8 could not be used because of clogging. These nine exploration holes and some groundwater observation holes (JCK1~JCK-12 in Figure 1) were used to analyse the leakage site of leachate of the old waste cell.

Results and discussion Groundwater temperature Using high-accuracy temperature measuring instruments to measure the temperature of drilling groundwater, the space between measuring points is 1 m. The groundwater temperature change range of each hole from the water surface to the hole bottom is shown in Table 1.

Downloaded from wmr.sagepub.com at RICE UNIV on May 19, 2015


Liu et al.

Figure 2.  Diagram of anti-seepage cushion structure of the new reservoir. Table 1.  Groundwater temperature of the holes. Hole




JCK-1 JCK-5 JCK-6 JCK-8 JCK-11 JCK-12 NZK-1 NZK-2

23.48~22.61 26.41~27.01 23.91~23.31 25.81~24.01 25.51~23.91 26.21~24.71 30.41~26.51 34.61~27.01

NZK-3 NZK-4 NZK-5 NZK-6 NZK-7 NZK-9 NZK-10

31.11~27.01 31.11~30.22 34.31~25.81 27.71~27.01 29.41~28.51 30.41~25.41 31.41~25.21  

There are several laws about temperature field. 1. The temperature of those six observation holes at the periphery of the reservoir (JCK-1~JCK-12) is generally lower than the temperature of those exploration holes in the dam A (NZK-1~NZK-10 in Figure 1). 2. The temperature on the same elevation surface is different, for instance, on the elevation surface of 20 m, the temperature of JCK-5 is 4 °C higher than JCK-1; the temperature of NZK1~NZK-10 on the 35 m elevation surface is shown in Table 2, the temperature of NZK-2, NZK-3, NZK-6 and NZK-7 is obvious higher than other holes. The zone where relative groundwater temperature is high on the same elevation surface can reflect main runoff parts of leachate, also the leakage site. The temperature difference is the result of the leachate leaking and uneven filtering; because of the relative high

temperature of the leachate, the groundwater temperature will increase at the filtering path after the leachate leaking. 3. The temperature of one hole is high in the upper and low in the lower, which conforms to the normal temperature rule at summer; the temperature change of JCK-5 is abnormal, it is low in the upper and high in the lower and the highest temperature is on the bottom of the hole, as seen in Figure 3.

Conductivity The conductivity instrument is highly accurate and has a temperature correction function which was used to measure the conductivity of groundwater in the hole; the space of the measuring points was 1 m. The results are shown in Table 3. The conductivity of local rainwater was 85 μS cm−1 during the testing time. From Table 3, the conductivity of NZK-1~NZK-10 is much bigger than the conductivity of local rainwater and groundwater in the holes of JCK-1~JCK-12, which shows that there is leachate in the groundwater under the impermeable membrane along dam A, but the leachate concentrations of those holes are different, the concentration of NZK-3 and NZK-5~NZK-6, NZK-9~NZK-10 is bigger.

Chroma By using the certain depth water sample collected technology in the hole, the water samples in the certain depth where the

Downloaded from wmr.sagepub.com at RICE UNIV on May 19, 2015


Waste Management & Research

Table 2.  The groundwater temperature on the 35 m elevation. Hole









Temperature /°C









Figure 3.  Groundwater temperature of JCK-5. Table 3.  Groundwater conductivity of each hole. Hole

Conductivity/ μS cm−1


Conductivity/ μS cm−1

JCK-1 JCK-5 JCK-6 JCK-8 JCK-11 JCK-12 NZK-1 NZK-2

107~211 199~202 (309) 1627~1693 225~314 461~807 803~947 7193~11,217 7569~10,557

NZK-3 NZK-4 NZK-5 NZK-6 NZK-7 NZK-9 NZK-10

8114~13,042 10,026~11,035 7359~14,172 12,712~15,009 4369~8664 12,684~13,249 8406~14,352  

maximum conductivity appeared were collected. The chroma of each water sample is shown in Figure 4. From Figure 4, the colour of the seven water samples NZK-2, NZK-3, NZK-5, NZK-6, NZK7, NZK-9 and NZK-10 is darker. Combined with the data of conductivity, there is positive correlation between the colour of the water samples and the conductivity. In addition, except for JCK-1, JCK-5 and JCK-8, the other groundwater is polluted in varying degrees. The leachate colour around holes NZK-6 and NZK-3 is the darkest, which indicates that these two zones around the two holes (NZK-6 and NZK-3) are the main leachate leakage sites. The leachate flows transversely through these two zones and pollutes the groundwater of the other holes, so that there is also leachate in the groundwater of other holes.

Figure 4.  Water samples of each hole.

(JCK-1, JCK-5… NZK-1… NZK-10 shown in Table 3 from left to right).

Horizontal flow velocity From the groundwater surface of each hole, the horizontal flow velocity test was done in the 1 m space between the measuring points. According to equation (1), the obtained groundwater horizontal flow velocity of each hole is shown in Table 4. The horizontal flow velocity of NZK-3, NZK-5 and NZK-6 is relatively bigger. The formation of dam A is a naturally strong weathered formation, and there is a certain uneven seepage velocity in this formation. The result of the flow velocity is consistent with the result from the temperature and conductivity analysis.

Summary The leachate in waste landfill is a kind of special contaminating fluid, and it has features such as, high conductivity, high chroma

Downloaded from wmr.sagepub.com at RICE UNIV on May 19, 2015


Liu et al. Table 4.  Groundwater horizontal flow velocity of holes.



Horizontal flow velocity/ m d−1


Horizontal flow velocity/ m d−1

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.


0.31~0.76 0.14~0.65 0.26~1.31 0.15~0.21 0.46~3.37

NZK-6 NZK-7 NZK-9 NZK-10

0.45~2.11 0.31~0.56 0.06~0.76 0.18~1.02  


and an increasing temperature. Meanwhile, the damage of the impermeable membrane makes the leachate leak into groundwater and makes the groundwater horizontal flow velocity increase under the impermeable membrane. Therefore, from the features of high groundwater conductivity under the impermeable membrane, high groundwater chroma, the abnormal temperature of the groundwater on the same elevation surface and increasing horizontal flow velocity, the leachate leakage site could be determined. Although the Yahu waste landfill site has been used for only a short time, the phenomenon of the damage of impermeable membrane and leachate polluting groundwater has emerged. From the result of a comprehensive tracer test and analysis of ten tracing exploration holes in dam A, the zone of NZK2~NZK-3 and the zone of NZK-6~NZK-7 is the main leakage site in dam A.

Declaration of conflicting interests The authors declare that there is no conflict of interest.

Dong T, Ma X-P, et al. (2014) Research on pollution situation of water environment landfill in Shenyang. Journal of Anhui Agriculture Science 42: 2698–2702 [in Chinese]. Guo X-J, Wu S-J and Ma Y-Y (2012) Quantitative investigation of landfillleachate contaminated sand soil with electrical resistivity method. Chinese Journal of Geotechnical Engineering 34: 2066–2071 [in Chinese]. Jiang X-X (2008) Prediction method for water quantity and water quality of leachate at sanitary landfill sites. Journal of Meteorology and Environment 24: 54–57 [in Chinese]. Liu H and Huang T (2010) Experimental study on the temperature change of municipal solid waste. Technology of Water Treatment 36: 61–65 [in Chinese]. Ning L-B and Chen J-D (2012) Forecast of groundwater pollution by a certain landfill leachate in Luoyang. Journal of Natural Science of Hunan Normal University 35: 89–92 [in Chinese]. Wang B, Wang Q and Dong L (2002) Comparison of leakage detection methods for landfill liners. Research of Environmental Sciences 15: 47–54 [in Chinese]. Yang H, Ge W-Y and Dong Z-G (2008) Study of mathematical model on coupling between temperature and seepage field in landfill site. Safety and Environmental Engineering 15: 63–66 [in Chinese]. Zhang W, Xue Q, Liu L and Liu J-J (2007) Research on the impact of seasonal climate change on the distribution of temperature in landfill. Chinese Journal of Underground Space and Engineering 3: 1541–1544 [in Chinese]. Zhang W, Chen Y and Zhan L (2008) Transport of leachate through vertical curtain grouting in landfills. Acta Scientiae Circumstantiae 28: 925–929 [in Chinese]. Zhu L, Wang W-L and Sun L-M (2005) Impact analysis of landfill in Jinan on the groundwater environment. Journal of Shandong University of Architecture and Engineering 20: 46–50 [in Chinese].

Downloaded from wmr.sagepub.com at RICE UNIV on May 19, 2015

Study on detecting leachate leakage of municipal solid waste landfill site.

The article studies the detection of the leakage passage of leachate in a waste landfill dam. The leachate of waste landfill has its own features, lik...
1MB Sizes 0 Downloads 8 Views