Waste Management xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Waste Management journal homepage: www.elsevier.com/locate/wasman
Characteristics and risks of secondary pollutants generation during compression and transfer of municipal solid waste in Shanghai Xiaoyuan Wang a, Bing Xie a,⇑, Dong Wu a, Muhammad Hassan a, Changying Huang b a b
Key Laboratory of Urbanization and Ecological Restoration of Shanghai, School of Ecology & Environmental Science, East China Normal University, Shanghai 200241, China Shanghai Environment Logistics Co., Ltd., Shanghai 200063, China
a r t i c l e
i n f o
Article history: Received 2 December 2014 Revised 27 June 2015 Accepted 2 July 2015 Available online xxxx Keywords: Municipal solid waste (MSW) MSW transfer station Transfer Secondary pollutants
a b s t r a c t The generation and seasonal variations of secondary pollutants were investigated during three municipal solid waste (MSW) compression and transfer in Shanghai, China. The results showed that the raw wastewater generated from three MSW transfer stations had pH of 4.2–6.0, COD 40,000–70,000 mg/L, BOD5 15,000–25,000 mg/L, ammonia nitrogen (NH3-N) 400–700 mg/L, total nitrogen (TN) 600–1500 mg/L, total phosphorus (TP) 50–200 mg/L and suspended solids (SS) 1000–80,000 mg/L. The pH, COD, BOD5 and NH3-N did not show regular change throughout the year while the concentration of TN, TP and SS were higher in summer and autumn. The animal and vegetable oil content was extremely high. The average produced raw wastewater of three transfer stations ranged from 2.3% to 8.4% of total refuse. The major air pollutants of H2S 0.01–0.17 mg/m3, NH3 0.75–1.8 mg/m3 in transfer stations, however, the regular seasonal change was not discovered. During the transfer process, the generated leachate in container had pH of 5.7–6.4, SS of 9120–32,475 mg/L. The COD and BOD5 were 41,633–89,060 mg/L and 18,116–34,130 mg/L respectively, higher than that in the compress process. The concentration of NH3-N and TP were 587–1422 mg/L and 80–216 mg/L, respectively, and both increased during transfer process. H2S, VOC, CH4 and NH3 were 0.4–4 mg/m3, 7–19 mg/m3, 0–3.4% and 1–4 mg/m3, respectively. The PCA analysis showed that the production of secondary pollutants is closely related to temperature, especially CH4. Therefore, avoiding high temperature is a key means of reducing the production of gaseous pollutants. And above all else, refuse classification in source, deodorization and anti-acid corrosion are the important processes to control the secondary pollutants during compression and transfer of MSW. Ó 2015 Elsevier Ltd. All rights reserved.
1. Introduction Large cities like Shanghai inevitably confront the municipal solid waste (MSW) issues, which is being exacerbated by the population and economic development. The output of MSW in Shanghai increased steadily, and daily amount of waste produced is around 20,000 tons in 2010 (Huang, 2013). As a result, the city risks being overwhelmed by waste if MSW cannot be removed and properly disposed in time. Therefore, waste collection and transfer is a major challenge and should be given priority to cope with the rapid population growth, and transfer stations play an important role in waste management system, serving as a link between a MSW collection scheme and the final waste disposal facilities (Tzipi et al., 2007). The current MSW collection and transport system in Shanghai mainly covers its subordinate districts where when solid waste ⇑ Corresponding author. E-mail address: [email protected] (B. Xie).
are collected and transported to landfill plant for final disposal (Che et al., 2014), which usually takes several days. Organic matter in waste may be converted into wastewater and gaseous pollutants such as CH4, H2S and VOC via the action of microorganisms during waste collection and transportation (Bareither et al., 2013) when conditions are available. Highly concentrated wastewater and some flammable and explosive gaseous pollutants will cause potential environmental and safety risks if discharged without proper treatment (Zairi et al., 2014; Schwarzbauer et al., 2002). So, a necessary step of management must be urgently taken to assess the environmental quality of each transfer station according to its proximity to the inhabited area. Although many studies either have assessed the ambient air quality at landfills and incineration sites, little is known about the pollutants generations and their regular emission patterns during the MSW compression and transports process. And this could largely reduce the MSW management efficiency in Shanghai city (Campos and Zapata, 2014). In this study, pollutants generation during compression and transfer in MSW transfer stations of Shanghai, their seasonal
http://dx.doi.org/10.1016/j.wasman.2015.07.005 0956-053X/Ó 2015 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Wang, X., et al. Characteristics and risks of secondary pollutants generation during compression and transfer of municipal solid waste in Shanghai. Waste Management (2015), http://dx.doi.org/10.1016/j.wasman.2015.07.005
2
X. Wang et al. / Waste Management xxx (2015) xxx–xxx
changes of wastewater and gaseous pollutants and the relationships between pollutant generation and operating and environmental conditions (temperature, amount of waste) were investigated. This study was a first attempt to conduct a synthetic evaluation of the secondary pollutants of the transfer station, aiming at incorporating environmental factors into a decision-making process. It is also expected to provide basic data for operation and management as well as pollution prevention and control in MSW management in the cities.
Table 1 Temperature and humidity of the whole year. Season
Temperature/°C
Humidity/%
Spring Summer Autumn Winter
12–22 24–36 23–10 8–10
30–84 36–72 28–60 11–57
2. Material and methods
on meteorology (QX/T 152-2012, 2012). The ranges of temperature and humidity of each season are listed in Table 1.
2.1. Characteristics of MSW in Shanghai
2.4. Sampling and analyzing methods
MSW is the mixture of a series of heterogeneous materials and usually categorized divided into organics and inorganics ones. The organics sets include food residue, wood waste, paper, textiles, rubber, and plastic (66.7%, 19.98%, 4.46%, 1.8%, 1.21% and 0.11%, respectively). Inorganics include ash (2.72%), tiles, glass (2.77%), metals (0.27%), and other inert materials. In organics MSW, the average contents of food residue, plastics, paper, textiles, wood waste and rubber were 66.7%, 19.98%, 4.46%, 1.8%, 1.21% and 0.11%, respectively. In the inorganics MSW, the average percentage of ash, glass and metal were 2.77%, 2.72% and 0.27%.
Raw wastewater (RW) and gas pollutants produced during compression were sampled in compression workshops, and the final effluent wastewater was sampled at the total discharge outlet. Leachate produced during transfer was sampled from the container sewage outlet and gas pollutants were sampled from the container vent pipes. These wastewater samples were collected in polyethylene bottles and stored at 4 °C for laboratory analysis. Parameters of wastewater samples include pH, COD, BOD5, NH3-N, SS, TN and TP were analyzed according to the Standard Methods (APHA-AWWA-WEF, 1998). Heavy metals in RW were analyzed with atomic absorption spectrometry (CAAM-2001EQ, China). H2S, CH4 and VOC were collected in the gas collecting bag and measured on site by odor sensor (IBIRD MAX6, USA). NH3 was absorbed in H2SO4 solution and analyzed. Wastewater amount calculation: The final effluent wastewater amount and RW amount were statistically summarized by daily flowmeter records. Wastewater generation rate was defined as wastewater weight accounting for total compressed waste weight (W/W%).
2.2. Sampling sites In order to cognize the secondary pollutants’ variation during the compression in MSW transfer stations, three MSW transfer stations located at different sites of Shanghai were selected: Hulin waste transfer station (HL) is in the north of Shanghai with a daily disposal capacity of ca. 1700 tons; Xupu waste transfer station (XP) is in the south-west of Shanghai with a daily disposal capacity of ca. 1600 tons; Tiandu waste transfer station (TD) is in the west of Shanghai with a daily disposal capacity of ca. 600 tons. The containers in the HL transfer station were selected to investigate the secondary pollutants’ variation during the transfer process. The size of the container used in the experiment was 5.7 2 2 m (length width height) (Fig. 1). Waste was horizontally compressed from the right into the container with a compactor in the MSW transfer station. After loaded, the container was placed at the wharf of the transfer station to simulate the transfer process. Two vent pipes were placed on the top to collect gas samples. An outlet pipe was placed on the bottom left to collect leachate samples. 2.3. Sampling time and environmental conditions Over 2 years, each transfer station was sampled 2 times every quarter with a sampling period of 4–7 d. Seasons are divided based
2.5. Statistical analysis To explore the correlation between pollutants and operating and environmental conditions, principal component analysis (PCA) is used for analyzing the correlations between quantitative variables, and finding clusters of relative groups of indicators (Wu et al., 2015). Four gas pollutants (H2S, VOC, CH4 and NH3) and six water index (pH, SS, COD, BOD5, NH3-N, TN and TP) were selected and combined with temperature, humidity and the waste mass. Varimax-normalized rotation was used to maximize the variances of factor loadings, and the number of significant principal factors was selected depending on the Kaiser criterion using PASW Statistics 18.0 (SPSS Inc., USA). One-way ANOVA analysis was carried to test for significant differences among parameters. The test was conducted on assumptions at 0.05 level of statistical significance. 3. Results and discussion 3.1. The influence of seasonal variation on RW pollutants during compression
Fig. 1. The simulation of experimental container. 1. Vent pipe; 2. Thermometer; 3. Sewage outlet; 4. Waste inlet.
3.1.1. Seasonal fluctuation of RW quality Fig. 2 presents the seasonal variation of pH, SS, COD, BOD5, NH3-N, TN and TP of RW generated from compressing process in the three transfer stations. Fig. 2(a) shows that the average pH value of the RW collected from three MSW transfer stations fluctuated from 4.2 to 6.0 during the four seasons. The pH from HL had the lowest value of 4.3, while the highest appeared in TD transfer station, averaging at 5.5 during the whole experiment. It was observed that pH had a lower value in spring than other seasons.
Please cite this article in press as: Wang, X., et al. Characteristics and risks of secondary pollutants generation during compression and transfer of municipal solid waste in Shanghai. Waste Management (2015), http://dx.doi.org/10.1016/j.wasman.2015.07.005
3
X. Wang et al. / Waste Management xxx (2015) xxx–xxx
8
120000
HL
(a)
XP
7
TD
HL
(b)
XP
100000
TD
6 80000
SS/mg·L-1
pH
5 4 3
60000 40000
2 20000
1 0
80000
0 Spring
Summer
Fall
Winter
Spring HL
(c)
30000
XP
70000
TD
Summer
Fall
Winter HL
(d)
XP TD
25000
BOD/mg·L-1
COD/mg·L-1
60000 50000 40000 30000
20000 15000 10000
20000 5000
10000 0
Summer
Fall
0
Winter
(e)
700
HL
1800
XP
1600
TD
600
Summer
Fall
Winter HL
(f)
XP TD
1200
500 400 300
1000 800 600
200
400
100
200
0
Spring
1400
TN/mg·L-1
Ammonia nitrogen/mg·L-1
800
Spring
Spring
Summer
Fall
0
Winter
Spring
250
Fall
Winter
HL
(g)
XP TD
200
TP/mg·L-1
Summer
150 100 50 0
Spring
Summer
Fall
Winter
Fig. 2. Seasonal variations of RW quality indicators (n = 18 (Winter)/24(Other seasons), n: No. of samples).
Overall, the RW discharged from the three transfer stations were weak acidic, which could mainly result from the acidification of organic matters in the waste (Kiddee et al., 2014). RW from the TD had the highest SS concentration during the whole year, ranging from 22,000 to 80,000 mg/L (Fig. 2b). HL was the lowest (max. 40,000 mg/L). Likewise, SS concentration of RW from XP in summer and winter were 40,000 and 10,000 mg/L
respectively. Generally, SS shows a higher level in summer and autumn and a lower level in spring and winter. From the Fig. 2(c), it can be seen that three transfer stations showed high COD levels, which kept around 40,000–50,000 mg/L in XP and HL within the whole year, respectively. And the COD value of TD even surged to 65,000 mg/L in winter. Likewise, COD and BOD5 of three waste transfer stations shared similar variation
Please cite this article in press as: Wang, X., et al. Characteristics and risks of secondary pollutants generation during compression and transfer of municipal solid waste in Shanghai. Waste Management (2015), http://dx.doi.org/10.1016/j.wasman.2015.07.005
4
X. Wang et al. / Waste Management xxx (2015) xxx–xxx
Table 2 Concentration of heavy metals and oil in RW of three waste transfer stations. Heavy metal
HL (n = 14)
XP (n = 14)
TD (n = 14)
Maximum allowable concentration (CJ343-2010)
Cu (mg/L) Cd (mg/L) Hg (mg/L) Pb (mg/L) As (mg/L) Cr (mg/L) Ni (mg/L) Petroleum (mg/L) Plant and animal oils (mg/L) Total oil (mg/L)
Contents lists available at ScienceDirect
Waste Management journal homepage: www.elsevier.com/locate/wasman
Characteristics and risks of secondary pollutants generation during compression and transfer of municipal solid waste in Shanghai Xiaoyuan Wang a, Bing Xie a,⇑, Dong Wu a, Muhammad Hassan a, Changying Huang b a b
Key Laboratory of Urbanization and Ecological Restoration of Shanghai, School of Ecology & Environmental Science, East China Normal University, Shanghai 200241, China Shanghai Environment Logistics Co., Ltd., Shanghai 200063, China
a r t i c l e
i n f o
Article history: Received 2 December 2014 Revised 27 June 2015 Accepted 2 July 2015 Available online xxxx Keywords: Municipal solid waste (MSW) MSW transfer station Transfer Secondary pollutants
a b s t r a c t The generation and seasonal variations of secondary pollutants were investigated during three municipal solid waste (MSW) compression and transfer in Shanghai, China. The results showed that the raw wastewater generated from three MSW transfer stations had pH of 4.2–6.0, COD 40,000–70,000 mg/L, BOD5 15,000–25,000 mg/L, ammonia nitrogen (NH3-N) 400–700 mg/L, total nitrogen (TN) 600–1500 mg/L, total phosphorus (TP) 50–200 mg/L and suspended solids (SS) 1000–80,000 mg/L. The pH, COD, BOD5 and NH3-N did not show regular change throughout the year while the concentration of TN, TP and SS were higher in summer and autumn. The animal and vegetable oil content was extremely high. The average produced raw wastewater of three transfer stations ranged from 2.3% to 8.4% of total refuse. The major air pollutants of H2S 0.01–0.17 mg/m3, NH3 0.75–1.8 mg/m3 in transfer stations, however, the regular seasonal change was not discovered. During the transfer process, the generated leachate in container had pH of 5.7–6.4, SS of 9120–32,475 mg/L. The COD and BOD5 were 41,633–89,060 mg/L and 18,116–34,130 mg/L respectively, higher than that in the compress process. The concentration of NH3-N and TP were 587–1422 mg/L and 80–216 mg/L, respectively, and both increased during transfer process. H2S, VOC, CH4 and NH3 were 0.4–4 mg/m3, 7–19 mg/m3, 0–3.4% and 1–4 mg/m3, respectively. The PCA analysis showed that the production of secondary pollutants is closely related to temperature, especially CH4. Therefore, avoiding high temperature is a key means of reducing the production of gaseous pollutants. And above all else, refuse classification in source, deodorization and anti-acid corrosion are the important processes to control the secondary pollutants during compression and transfer of MSW. Ó 2015 Elsevier Ltd. All rights reserved.
1. Introduction Large cities like Shanghai inevitably confront the municipal solid waste (MSW) issues, which is being exacerbated by the population and economic development. The output of MSW in Shanghai increased steadily, and daily amount of waste produced is around 20,000 tons in 2010 (Huang, 2013). As a result, the city risks being overwhelmed by waste if MSW cannot be removed and properly disposed in time. Therefore, waste collection and transfer is a major challenge and should be given priority to cope with the rapid population growth, and transfer stations play an important role in waste management system, serving as a link between a MSW collection scheme and the final waste disposal facilities (Tzipi et al., 2007). The current MSW collection and transport system in Shanghai mainly covers its subordinate districts where when solid waste ⇑ Corresponding author. E-mail address: [email protected] (B. Xie).
are collected and transported to landfill plant for final disposal (Che et al., 2014), which usually takes several days. Organic matter in waste may be converted into wastewater and gaseous pollutants such as CH4, H2S and VOC via the action of microorganisms during waste collection and transportation (Bareither et al., 2013) when conditions are available. Highly concentrated wastewater and some flammable and explosive gaseous pollutants will cause potential environmental and safety risks if discharged without proper treatment (Zairi et al., 2014; Schwarzbauer et al., 2002). So, a necessary step of management must be urgently taken to assess the environmental quality of each transfer station according to its proximity to the inhabited area. Although many studies either have assessed the ambient air quality at landfills and incineration sites, little is known about the pollutants generations and their regular emission patterns during the MSW compression and transports process. And this could largely reduce the MSW management efficiency in Shanghai city (Campos and Zapata, 2014). In this study, pollutants generation during compression and transfer in MSW transfer stations of Shanghai, their seasonal
http://dx.doi.org/10.1016/j.wasman.2015.07.005 0956-053X/Ó 2015 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Wang, X., et al. Characteristics and risks of secondary pollutants generation during compression and transfer of municipal solid waste in Shanghai. Waste Management (2015), http://dx.doi.org/10.1016/j.wasman.2015.07.005
2
X. Wang et al. / Waste Management xxx (2015) xxx–xxx
changes of wastewater and gaseous pollutants and the relationships between pollutant generation and operating and environmental conditions (temperature, amount of waste) were investigated. This study was a first attempt to conduct a synthetic evaluation of the secondary pollutants of the transfer station, aiming at incorporating environmental factors into a decision-making process. It is also expected to provide basic data for operation and management as well as pollution prevention and control in MSW management in the cities.
Table 1 Temperature and humidity of the whole year. Season
Temperature/°C
Humidity/%
Spring Summer Autumn Winter
12–22 24–36 23–10 8–10
30–84 36–72 28–60 11–57
2. Material and methods
on meteorology (QX/T 152-2012, 2012). The ranges of temperature and humidity of each season are listed in Table 1.
2.1. Characteristics of MSW in Shanghai
2.4. Sampling and analyzing methods
MSW is the mixture of a series of heterogeneous materials and usually categorized divided into organics and inorganics ones. The organics sets include food residue, wood waste, paper, textiles, rubber, and plastic (66.7%, 19.98%, 4.46%, 1.8%, 1.21% and 0.11%, respectively). Inorganics include ash (2.72%), tiles, glass (2.77%), metals (0.27%), and other inert materials. In organics MSW, the average contents of food residue, plastics, paper, textiles, wood waste and rubber were 66.7%, 19.98%, 4.46%, 1.8%, 1.21% and 0.11%, respectively. In the inorganics MSW, the average percentage of ash, glass and metal were 2.77%, 2.72% and 0.27%.
Raw wastewater (RW) and gas pollutants produced during compression were sampled in compression workshops, and the final effluent wastewater was sampled at the total discharge outlet. Leachate produced during transfer was sampled from the container sewage outlet and gas pollutants were sampled from the container vent pipes. These wastewater samples were collected in polyethylene bottles and stored at 4 °C for laboratory analysis. Parameters of wastewater samples include pH, COD, BOD5, NH3-N, SS, TN and TP were analyzed according to the Standard Methods (APHA-AWWA-WEF, 1998). Heavy metals in RW were analyzed with atomic absorption spectrometry (CAAM-2001EQ, China). H2S, CH4 and VOC were collected in the gas collecting bag and measured on site by odor sensor (IBIRD MAX6, USA). NH3 was absorbed in H2SO4 solution and analyzed. Wastewater amount calculation: The final effluent wastewater amount and RW amount were statistically summarized by daily flowmeter records. Wastewater generation rate was defined as wastewater weight accounting for total compressed waste weight (W/W%).
2.2. Sampling sites In order to cognize the secondary pollutants’ variation during the compression in MSW transfer stations, three MSW transfer stations located at different sites of Shanghai were selected: Hulin waste transfer station (HL) is in the north of Shanghai with a daily disposal capacity of ca. 1700 tons; Xupu waste transfer station (XP) is in the south-west of Shanghai with a daily disposal capacity of ca. 1600 tons; Tiandu waste transfer station (TD) is in the west of Shanghai with a daily disposal capacity of ca. 600 tons. The containers in the HL transfer station were selected to investigate the secondary pollutants’ variation during the transfer process. The size of the container used in the experiment was 5.7 2 2 m (length width height) (Fig. 1). Waste was horizontally compressed from the right into the container with a compactor in the MSW transfer station. After loaded, the container was placed at the wharf of the transfer station to simulate the transfer process. Two vent pipes were placed on the top to collect gas samples. An outlet pipe was placed on the bottom left to collect leachate samples. 2.3. Sampling time and environmental conditions Over 2 years, each transfer station was sampled 2 times every quarter with a sampling period of 4–7 d. Seasons are divided based
2.5. Statistical analysis To explore the correlation between pollutants and operating and environmental conditions, principal component analysis (PCA) is used for analyzing the correlations between quantitative variables, and finding clusters of relative groups of indicators (Wu et al., 2015). Four gas pollutants (H2S, VOC, CH4 and NH3) and six water index (pH, SS, COD, BOD5, NH3-N, TN and TP) were selected and combined with temperature, humidity and the waste mass. Varimax-normalized rotation was used to maximize the variances of factor loadings, and the number of significant principal factors was selected depending on the Kaiser criterion using PASW Statistics 18.0 (SPSS Inc., USA). One-way ANOVA analysis was carried to test for significant differences among parameters. The test was conducted on assumptions at 0.05 level of statistical significance. 3. Results and discussion 3.1. The influence of seasonal variation on RW pollutants during compression
Fig. 1. The simulation of experimental container. 1. Vent pipe; 2. Thermometer; 3. Sewage outlet; 4. Waste inlet.
3.1.1. Seasonal fluctuation of RW quality Fig. 2 presents the seasonal variation of pH, SS, COD, BOD5, NH3-N, TN and TP of RW generated from compressing process in the three transfer stations. Fig. 2(a) shows that the average pH value of the RW collected from three MSW transfer stations fluctuated from 4.2 to 6.0 during the four seasons. The pH from HL had the lowest value of 4.3, while the highest appeared in TD transfer station, averaging at 5.5 during the whole experiment. It was observed that pH had a lower value in spring than other seasons.
Please cite this article in press as: Wang, X., et al. Characteristics and risks of secondary pollutants generation during compression and transfer of municipal solid waste in Shanghai. Waste Management (2015), http://dx.doi.org/10.1016/j.wasman.2015.07.005
3
X. Wang et al. / Waste Management xxx (2015) xxx–xxx
8
120000
HL
(a)
XP
7
TD
HL
(b)
XP
100000
TD
6 80000
SS/mg·L-1
pH
5 4 3
60000 40000
2 20000
1 0
80000
0 Spring
Summer
Fall
Winter
Spring HL
(c)
30000
XP
70000
TD
Summer
Fall
Winter HL
(d)
XP TD
25000
BOD/mg·L-1
COD/mg·L-1
60000 50000 40000 30000
20000 15000 10000
20000 5000
10000 0
Summer
Fall
0
Winter
(e)
700
HL
1800
XP
1600
TD
600
Summer
Fall
Winter HL
(f)
XP TD
1200
500 400 300
1000 800 600
200
400
100
200
0
Spring
1400
TN/mg·L-1
Ammonia nitrogen/mg·L-1
800
Spring
Spring
Summer
Fall
0
Winter
Spring
250
Fall
Winter
HL
(g)
XP TD
200
TP/mg·L-1
Summer
150 100 50 0
Spring
Summer
Fall
Winter
Fig. 2. Seasonal variations of RW quality indicators (n = 18 (Winter)/24(Other seasons), n: No. of samples).
Overall, the RW discharged from the three transfer stations were weak acidic, which could mainly result from the acidification of organic matters in the waste (Kiddee et al., 2014). RW from the TD had the highest SS concentration during the whole year, ranging from 22,000 to 80,000 mg/L (Fig. 2b). HL was the lowest (max. 40,000 mg/L). Likewise, SS concentration of RW from XP in summer and winter were 40,000 and 10,000 mg/L
respectively. Generally, SS shows a higher level in summer and autumn and a lower level in spring and winter. From the Fig. 2(c), it can be seen that three transfer stations showed high COD levels, which kept around 40,000–50,000 mg/L in XP and HL within the whole year, respectively. And the COD value of TD even surged to 65,000 mg/L in winter. Likewise, COD and BOD5 of three waste transfer stations shared similar variation
Please cite this article in press as: Wang, X., et al. Characteristics and risks of secondary pollutants generation during compression and transfer of municipal solid waste in Shanghai. Waste Management (2015), http://dx.doi.org/10.1016/j.wasman.2015.07.005
4
X. Wang et al. / Waste Management xxx (2015) xxx–xxx
Table 2 Concentration of heavy metals and oil in RW of three waste transfer stations. Heavy metal
HL (n = 14)
XP (n = 14)
TD (n = 14)
Maximum allowable concentration (CJ343-2010)
Cu (mg/L) Cd (mg/L) Hg (mg/L) Pb (mg/L) As (mg/L) Cr (mg/L) Ni (mg/L) Petroleum (mg/L) Plant and animal oils (mg/L) Total oil (mg/L)
