Journal of Science and Technology in Civil Engineering NUCE 2018. 12 (3): 113–122
EVALUATION OF THE QUALITY OF DRAINAGE SLUDGE
IN TO LICH RIVER BASIN AND THE PROPOSAL
OF SUITABLE MANAGEMENT SOLUTIONS
Tran Duc Ha
a,∗
, Tran Thuy Anh
a
, Tran Duc Minh Hai
a
a
Faculty of Environmental Engineering, National University of Civil Engineering,
55 Giai Phong road, Hai Ba Trung district, Hanoi, Vietnam
Article history:
Received 20 March 2018, Revised 05 April 2018, Accepted 27 April 2018
Abstract
This study aims to examine the characteristics and to assess the hazardous level as well as the reusability of
sewage sludge and river sediment from To Lich River (TLR) basin, which is the largest wastewater catch-
ment in Hanoi. Sludge samples were collected from six manholes along Tran Binh Trong (TBT) and Thai
Ha (TH) sewers in rainy and dry seasons. Sediment samples were collected from seven sites near principal
wastewater and storm water discharging points along TLR upstream in dry season. Parameters, such as pH,
humidity, total ash, zinc (Zn), copper (Cu), lead (Pb), and cadmium (Cd) in sewage sludge were examined.
Trace metals in TLR sediment, e.g. arsenic (As), mercury (Hg), lead (Pb), zinc (Zn), chromium (Cr), and
cadmium (Cd) were analyzed. The results of sludge and sediment analysis were then compared with national
environmental regulations for hazards and aquatic life preservation, and land use purposes, including QCVN
43:2012
/BTNMT, QCVN 50:2013/BTNMT, QCVN 03-MT: 2015/BTNMT. The majority of examined parame-
ters of sewage sludge, except ash content, are higher in dry seasons than in rainy seasons. Regarding hazardous
level, all the investigated heavy metals in sewage sludge in dry and rainy seasons, respectively, as followings:
644 and 598 mg·kg
−1
Zn, 146.5 and 127.3 mg·kg
−1
Cu, 71.2 and 69.5 mg·kg
−1
Pb, and 1.51 and 1.46 mg·kg
−1
Cd, are below the legislated thresholds, thus, can be considered as nontoxic. Reusability of sewage sludge,
however, should be considered since Zn exceeded permissible values for all of land use purposes. The con-
centration of As (0.659 mg·kg
−1
), Hg (0.03 mg·kg
−1
), Pb (4.07 mg·kg
−1
), Zn (81.3 mg·kg
−1
), and Cd (0.078
mg·kg
−1
) meets national standards on hazardous waste, and sludge from water treatment process, as well as to
protect aquatic life and to be reused in anthropogenic activities. However, Cr concentration (157 mg·kg
−1
) is
above those legislated thresholds, thus, unsuitable to be reused as land or fertilizer. With high concentration of
several trace metals and humidity, drainage sludge from TLR basins should be treated to improve its reusability.
Keywords:
sewage sludge; river sediment; sludge management; To Lich River; heavy metal; national technical
regulation.
c
2018 National University of Civil Engineering
1. Introduction
Yen So landfill, with the area of 14.1 hectare, is currently receiving all of the dredged sludge
generated from sewers, canals, rivers, lakes, and wastewater treatment plants in the inner city of
∗
Corresponding author. E-mail address:
hatd@nuce.edu.vn
(Ha, T. D.)
113
Ha, T. D. et al.
/ Journal of Science and Technology in Civil Engineering
Hanoi [
1
]. Sewage sludge, with the large amount of approximately 160,000 to 200,000 tons per year,
is the dominant component of Hanoi drainage system. In addition to the above sludge, approximate
1.4 milions tons of dredged sediment from the West Lake will be transported to Yen So landfill site
in 2018 [
2
]. Due to the large amount of the dredged sludge, that site may face to the risk of being
overloaded. On the other hand, when being disposed or reused for agricultural purposes, pollutant-
containing sludge and sediment may cause the contamination of the surrounding environment of the
landfills [
3
,
4
]. Therefore, it is necessary to assess the level of hazards and the reusability of Hanoi
drainage sludge before it is transported to Yen So landfill.
To Lich River (TLR) is the main wastewater- receiving river in the inner city of Hanoi. Before
discharged into the river, wastewater and storm water in the basin of TLR flow through the combined
drainage network consisting of sewers, canals, and regulating ponds. Sludge generated in the basin
is composed of two types including sewage sludge from the network and sediment from the river
bed. Those types are usually dredged with di
fferent frequency and at different time. Sediment in the
TLR is dredged every 2 years [
1
,
5
]. Although many previous studies [
6
–
12
] focused on the quality
of TLR sediment, as far as our knowledge, few researches have evaluated sludge characteristics of
sewage sludge from that basin.
Previous studies showed the contamination of TLR sediment with high concentration of trace met-
als [
6
–
9
]. These concentrations exceeded acceptable values for sediment and were considered toxic
for aquatic life in the river [
10
–
12
]. TLR sediment was also considered to be unsuitable for land use
purposes in agriculture, forestry, industry, commerce and service, or for crop fertilizers [
13
]. Heavy
metals in TLR sediment were mostly generated from anthropogenic activities, such as the discharge of
untreated domestic and industrial wastewater from residence and industrial clusters upstream [
9
,
11
].
However, those conclusions based on the analysis of sediment samples collected before recent ac-
tivities to improve the quality of sediment and river water are being implemented. Since 2012, the
new system of environmental protection regulations has been tightened together with the relocation
of industrial facilities out of the river basin and embankment of the river banks. Therefore, the current
quality of TLR sediment may be di
fferent from previous studies.
This study focuses on the characteristics of the dredged sewage sludge and river sediment from
TLR basin recently. Analysis results of sludge quality will clarify the possible toxicants and the
reusability of the sludge and sediment for various purposes. Understanding the characteristics of
drainage sludge provides the basis for the proper sludge management and reduces the risk of overload
and pollution for Yen So landfill site.
2. Materials and methods
2.1. Study area and sample collection
TLR originates from the West Lake and runs through Hanoi inner city before merging with Kim
Nguu River downstream and flowing into Nhue River. It has a length of 14 km and covers the basin
of 77.5 square kilometers, which is the largest drainage catchment in Hanoi. The total amount of
wastewater discharged into TLR is approximately 290,000 m
3
per day [
9
]. The drainage network
in the TLR basin was built to collect wastewater both from the ancient city, where there are no new
construction activities and in the new urban areas, where the infrastructure is still being completed.
Sampling locations of sediment and sludge were illustrated in Fig.
1
. Sediment samples were col-
lected from seven points near the crossing bridges along 7-km TLR upstream which receives wastew-
ater and storm water from the main sewers. Two targeted sewers in this study were Tran Binh Trong
114
Ha, T. D. et al.
/ Journal of Science and Technology in Civil Engineering
Ha, T. D. et al./ Journal of Science and Technology in Civil Engineering
untreated domestic and industrial wastewater from residence and industrial clusters upstream [9, 11]. However, those conclusions
based on the analysis of sediment samples collected before recent activities to improve the quality of sediment and river water are
being implemented. Since 2012, the new system of environmental protection regulations has been tightened together with the
relocation of industrial facilities out of the river basin and embankment of the river banks. Therefore, the current quality of TLR
sediment may be different from previous studies.
This study focuses on the characteristics of the dredged sewage sludge and river sediment from TLR basin recently. Analysis
results of sludge quality will clarify the possible toxicants and the reusability of the sludge and sediment for various purposes.
Understanding the characteristics of drainage sludge provides the basis for the proper sludge management and reduces the risk of
overload and pollution for Yen So landfill site.