Chart of Suspended Sediment in Rivers and Lakes Area of ​​Hon Gai Coal Mine Cluster in 2005 2009

Coal sorting plant I, using screening technology to separate dry coal dust, manually selecting large lump coal and the remaining coal using inclined washing troughs, recovering peat using a system of tower settling tanks and natural settling pits. Water from the screening process arises as follows: water in the industrial cleaning process, water overflowing tanks, discharge bottoms, and peat reservoirs. The water sources generated at this stage are mainly mixed with coal dust. If not treated promptly, it will affect the receiving environment.

Coal sorting plant II uses suspension screening technology, wastewater is generated during the coal sorting stage.

Coal Entrainment Plant III uses advanced technology so it does not generate wastewater during the production process. Wastewater used in watering and dust suppression process.

The capacity of Cua Ong coal processing company is 12 - 14 million tons/year.

The total volume of water supplied to the screening screen is 30,000 m 3 /day, taken from Bara Lake (a natural reservoir supplied from the Mong Duong River).

Wastewater from the screening process in factories has been put into sedimentation pits and recirculated sludge pits, no production wastewater is dumped into the environment.

* Evaluate wastewater quality

Wastewater from screening activities contains coal dust and a large amount of suspended solids, thus affecting the surface water environment in the area. Causes sedimentation of water bodies around the project due to solid waste generated. During the exploitation process, it will cause fluctuations in the hydrological network. According to the results of research on the surface water environment in the surrounding area, it shows that most of the surface water environment around the study area is acidic, the amount of CO2 in the water is high, so it has the ability to corrode metals and concrete . . The hardness of water is high, due to the dissolution of mine waste. In addition, when wastewater flows through the drainage system, it carries organic matter, garbage, animal and plant remains, oil and grease...

b. Hon Gai Coal Selection Company

Wastewater generated from screening activities contains many pollutants, with increased levels of organic substances and heavy metals. Source of pollution

Contamination is from waste rock and dust during the screening process. All water there is recovered and reused to the maximum level, to minimize impact on the environment. Through the research and evaluation of the facilities we have.

mg/l 300







Figure 2.10: Evolution of suspended sediment in rivers and lakes in the region

Hon Gai mine cluster in 2005-2009

Khe Fish Lake Ha Tu Stream Lo Phong Stream Gia Khau Stream Khe Sinh Stream - Saltwater Bridge

Hoanh Bo






The stream intersection crosses the ground +48 Cao


T clears

Figure 2.12: Evolution of Fe content in surface water

Hon Gai area in 2005-2009

Figure 3.6: Chart of suspended sediment evolution in rivers and lakes in the Hon Gai coal mine cluster in 2005 2009

mg/l 4





Khe Ca Lake

Ha Tu Stream

Saltwater Bridge of Giap Khau Stream Khe Sinh Stream-

Hoanh Bo






QCVN 08:2008:BTNMT (Gh B)

Figure 3.7: Graph showing the evolution of Fe content in surface water in Hong Gai area in the years 2005-2009 [25]

The sludge recovery system is not thorough, still allowing the natural sludge lake to occupy a large area and discharge water into the environment (Cua Ong Coal Screening Plant;

Hon Gai). Currently, Hon Gai Coal Processing Company has invested in a peat flotation system combined with a pressurized filter press system. The products after screening and filtering are bran 3 and waste rock. These products all have a moisture content of W≤20%, this technology ensures maximum recovery of circulating water.

3.2.2. Wastewater from underground mining

* Wastewater from the process of digging the furnace, cutting coal, and transporting coal in the furnace.

Because the furnaces are dug straight along the seam, the slope of the furnace road changes up and down. There are sections where the furnace is sunken between the two slope tops, so water cannot flow. These areas are forced to be drained using local pumps.

To drain water from stagnant water points at furnaces along the seam, it is expected that each stagnant water position will be arranged with a pump, pumping water through water pipes to gutter positions so that it can flow to the central water tank at the level. – 140 and – 350 at the platforms next to the well so that the central water pumping station pumps water to the industrial yard at level + 35.

According to the design of the project, all water that needs to be drained during the exploitation process of Nui Beo Coal Mine with a flow of 1155 - 1462 m 3 /h is brought to level - 350 and then pumped to the ground.

The quality of mine wastewater is mildly acidic, the content of iron and manganese exceeds allowed standards, and other monitoring parameters meet QCVN 24:2009/BTNMT type B. Therefore, the Company's mine wastewater will treated to meet allowed standards before being discharged into the receiving stream of Ha Tu Stream.

* Production activities on site.

On the +35 industrial yard area, a screening workshop will be built to screen coal before bringing it to the Nui Beo coal processing plant, raw coal storage, finished coal storage, and auxiliary works such as: dormitory, bathroom, laundry, cafeteria and supporting factories....

Therefore, when the project comes into operation, it will generate wastewater (domestic wastewater, industrial wastewater due to factory operations, rainwater overflowing through coal storage areas and coal screening areas) and waste. Solid waste has the potential to impact

surface water quality of the area. The level of this impact is not large, because the mine already has mine wastewater treatment systems, oil and grease treatment and domestic wastewater treatment that meet allowed standards.

* Domestic wastewater.

The total amount of water supplied for daily use when the project comes into stable operation is 200m 3 /day and night. Therefore, the amount of domestic wastewater generated is calculated as 80% of the water supply, respectively:

80% x 200 m 3 = 160 m 3 / day and night (2100 people)

Domestic wastewater is often divided into two types: gray water and water


Gray water is water for bathing and washing, water from the kitchen process (3/4 volume) Black water is water collected from toilets (1/4 volume)

According to the design of the project, the water of the toilet areas is collected and collected

treated in septic tanks built underground under toilets. After storing the water here, it will be sucked up and treated by the Environmental Sanitation Company. Therefore, only 3/4 of the amount of domestic wastewater passing through temporary manholes and not being thoroughly treated will have an impact on surface water quality.

According to standard 20 TCN-51-84, it is possible to estimate the content of pollutants that will be introduced into the stream without going through the treatment system as shown in table 3.12.

Table 3.12. The content of pollutants in wastewater discharged into streams (when there are no mitigation measures) according to standard 20 TCN-51-84



Total volume of waste


Concentration of pollutants in wastewater


QCVN 14:2008/BTNMT

(column B)






Floating solids







BOD 5 of settled water







N-NH 4 +





Total phosphorus




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Chart of Suspended Sediment in Rivers and Lakes Area of ​​Hon Gai Coal Mine Cluster in 2005 2009

According to Table 3.12, the quality of domestic wastewater is forecast to be polluted with the parameters TSS, BOD, total Nitrogen, total Phosphorus, and Coliform. Therefore, domestic wastewater will be treated by the company to meet QCCP standards before being discharged into the receiving source, Ha Tu stream.

* Rainwater overflows.

The total industrial production area of ​​the mine according to the project's calculations is: 45,500 m 2 . The average annual rainfall of the Hon Gai area is about 1,619 mm/year, the highest rainfall in a day in the area is: rainwater runoff on the ground only accounts for about 2% of the amount of rainwater falling on the ground.

The amount of rainwater runoff over the production surface of Nui Beo coal mine is about 147,329 m 3 /year.

Rainwater that flows over the surface of the production area often has high solid content (from 100 - 1500 mg/l), and also contains oil and grease. If the estimated solid content washed away by rainwater running over the Nui Beo coal mine production site is 1,500 mg/l, the total amount of solids brought into Ha Tu stream per year is 220,994 tons/year.

The above calculation shows that if there are no mitigation measures, solids will be introduced into the stream bed, causing sedimentation of the stream bed, while reducing the self-assimilation ability of the stream, increasing the possibility of causing pollution in stream water. . In addition, rainwater runoff also introduces many other pollutants into streams. The Ha Tu stream flowing through is the place that receives most of the solids and oils from rainwater flowing over the total mine area.

The amount of rainwater runoff over the entire project area is calculated to be 2,661.75 m 3 /day and night.

The amount of wastewater generated from underground mining activities will be collected by the company, treated by treatment works invested by the coal-mineral industry group, and then released into the environment.

3.2.3. Rainwater flows over the field

According to the " Strategic Environmental Assessment Report (SEA) Coal Industry Development Planning to 2020, with a view to 2030" , the dangers caused by wastewater pollution from coal mines belonging to the Coal and Minerals have become urgent.

The amount of wastewater from the mine depends on the coal mining output each year. Based on data declaring and paying environmental protection fees for industrial wastewater of units in the coal industry, the total amount of wastewater from the mine (in 2009) was 38,914,075m 3 . Two typical parameters affecting the environment of mine wastewater are pH and suspended sediment, heavy metals (iron, manganese). In which the pH ranges from 3.1 to 6.5, the suspended solids content is 1.7 to 2.4 times higher than the allowed threshold. Therefore, wastewater from mines causes many impacts on river systems,

streams and lakes in coastal areas - causing sedimentation, loss of aquatic resources, and deterioration of water quality. In particular, pollution in the mining area is cumulative pollution, combined with the impact of illegal coal mining over a long period of time, leading to a situation where some lakes and ponds in the Cam Pha area have become acidified, affecting the water quality for agriculture.

Results of wastewater analysis in 2010 at some mines in Quang Ninh province show that wastewater from mines often contains high color and low pH. Wastewater at Coc Sau, Cao Son, Mong Duong mines... all have suspended matter content higher than allowed standards. Almost all wastewater from coal mines is contaminated with manganese, exceeding allowable standards.

The impact of mine wastewater has caused the quality of surface water in rivers, streams, and lakes in the vicinity of coal mines to decline. In particular, surface water quality in Quang Ninh shows signs of severe pollution.

According to calculations, the load of pollutants in mining water and wastewater from factories shows:

- The acidity of mine wastewater varies seasonally and depends on the sulfur content. However, the wastewater from Nui Beo mine is quite strongly acidic in the dry season, pH=5.5. [28]

- Suspended sediment content in wastewater is high, exceeding allowable standards.

- There are many heavy metals e, Mn, and non-metals that can pollute surface water.

Although the content of potentially polluting substances in wastewater is small, due to the large amount of wastewater, it will still pollute surface water in the area.

Table 3.13. The amount of water drained from the seams



Amount of water drained

Rainy season

Dry season


Sidewalk 14 East Wing




Sidewalk 14 West Wing




Sidewalks 11 and 13 widened



(Source: EIA project to expand capacity of Nui Beo coal mine)

In addition, wastewater from auxiliary manufacturing workshops, mechanical repair, car washing, contains oil, grease, suspended sediment, coal and a small amount of metals discharged into streams that can cause pollution if not take mitigation measures at the source.

3.2.4. Rainwater flows through coal warehouses

Most of the locations of workshops and coal warehouses have not changed, so the impact of rainwater runoff through these premises has been evaluated. Rainwater in coal warehouses often brings in solids and dust, affecting the surface water environment of the area. Most coal warehouses do not have roofs, so rainwater easily washes away coal and dirt. The pH of mine wastewater always ranges from 3.1 - 6.5. Suspended residue content often exceeds QCVN by 2-3 times. According to an assessment by a unit in the group, wastewater from coal mines is causing many negative impacts on the environment of rivers, streams, and coastal areas such as causing sedimentation, loss of aquatic resources, and deterioration of water quality. ...

In Hon Gai and Cam Pha areas, water quality has changed fundamentally, rich in sulfate ions, reduced in bicarbonate ions, and acidic. Water resources are reduced in both quality and reserve.

3.2.5. Rainwater overflows through the coal port

Table 3.14. Rainwater flows over some coal ports





Amount of water

overflowing rain


Chemical port

Mong Duong

Mong Duong –

Cam Pha

16,382 m2

3,800 m 3 /day



Khe Day Port

Cua Ong –

Cam Pha

34,143 m2

2,918 m 3 /day



Nam Cau Port


Hong Ha – Ha


20,000 m2

2,900 m 3 /day


(Source: Investigation by student Vu Xuan Lich)

Rainwater flows through coal storage yards, carrying scattered coal into the water source, increasing the concentration of pollutants in the water, mainly suspended sediment and heavy metals.

At coal ports, the situation of transporting and loading coal in the "absolute protection zone" still exists. Many large tonnage ships coming to receive coal cannot enter the port and have to use transshipment methods, so a large amount of coal is scattered into Ha Long Bay. Report on the current state of the environment in Ha Long Bay in 2010 said: in coastal areas of Ha Long Bay, there have been signs of local pollution due to increased amount of suspended solids (TSS), decreased amount of dissolved oxygen (DO). ); Nitririte and Coliform disease-causing bacteria at the southern coastal coal port of Cau Trang... have caused turbidity to approximate or exceed allowable standards.

The quality of coastal sea water at some coal loading ports of coal processing plants and coal loading docks at coal ports of companies is also polluted or beginning to be polluted due to suspended sediment and although it tends to decrease gradually, still higher than the allowable limit. There were times when monitoring in the Hon Gai - Cam Pha area (Quang Ninh) determined that ammonium exceeded the limit in aquaculture and aquatic conservation areas. Particularly, coastal oil and grease in Quang Ninh has been polluted from mild to severe levels,

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