(Luận văn thạc sĩ) evaluation of the efficiency of the liquid waste treatment system in coal mining at khanh hoa coal mine

THAI NGUYEN UNIVERSITY UNIVERSITY OF AGRICULTURAL AND FORESTRY NGUYEN THI HANG EVALUATION OF THE EFFICIENCY OF THE LIQUID WASTE TREATMENT SYSTEM IN COAL MINING AT KHANH HOA COAL MINE

THAI NGUYEN UNIVERSITY

UNIVERSITY OF AGRICULTURAL AND FORESTRY

NGUYEN THI HANG

EVALUATION OF THE EFFICIENCY OF THE LIQUID WASTE TREATMENT SYSTEM IN COAL MINING AT KHANH HOA COAL MINE

BACHELOR THESIS

Study Mode: Full-time Major: Environmental science and management Faculty: International Programs Office

Batch: 2015 - 2020

Thai Nguyen, 20/11/2020

ACKNOWLEDGEMENT

Over the internship at Khanh Hoa-VVMI Coal Company where it is very suitable for the environment industry

Here, we have initially grasped:

- Diagram of coal mining process;

- Discharge from coal mining;

- Methods of wastewater treatment during coal mining;

During my internship, I have strictly follow all the rules of the company set out, try, actively study, grasp the labor safety process During my internship, I have strictly follow all the rules of the company set out, try, actively study, grasp the labor safety process With the knowledge learned on the school chair combined with practical observation, through this internship has helped me to add knowledge and learn experience working for myself

With the knowledge learned on the school chair combined with practical observation, through this internship has helped me to add knowledge and learn experience working for myself

In order to complete this internship report, in addition to my efforts, I would like to express my deep gratitude to:

In order to complete this internship report, in addition to my efforts, I would like to express my deep gratitude to:

- The teachers of the advanced program have dedicatedly taught in the past semesters, especially thanking the instructor Mr Nguyen Huu Tho for dedicatedly guiding me to complete this internship

- The board of directors and employees of Khanh Hoa-VVMI Coal Company have dedicatedly guided and facilitated me to complete this internship

Due to the short internship time, my ability is limited and initially approaching the reality is still very difficult, so I can not avoid mistakes, I look forward to receiving the sympathy and suggestions of teachers and friends

Thank you very much!

PART I INTRODUCTION 1.1 Research rationale

Natural resources are material assets available in nature that humans can exploit, process, use and serve human life (forests, animals, plants, mineral deposits, water, oil, and gas, ) It is an essential part of the environment and has

a close relationship with the environment Natural resources bring a lot of benefits to people, but the exploitation and use of resources are not reasonable, the management is not strict and ineffective, leading to the loss and waste of natural resources countries in general and Vietnam in particular

In the trend of integration and development, our country's industries are interested in investing and promoting Among them are activities of the mining and mineral processing industry Coal mining is an activity that has been interested in investment and development for a long time Coal provides fuel sources for many economic sectors such as thermal power, cement, metallurgy, The demand for coal is increasing, coal mining and processing activities are therefore continuously increasing Besides the economic benefits that the coal mining industry brings, this activity causes coal reserves to decline, but coal is a non-renewable resource and it also causes negative impacts on the environment requires investors to have appropriate management solutions, technology solutions, and treatment solutions to minimize negative impacts on the environment

Thai Nguyen is a province with large coal reserves, with many coal mines being exploited such as the Khanh Hoa coal mine, Phan Me coal mine, Nui Hong coal mine Khanh Hoa is a large coal mine located in the North of Thai Nguyen

city Originally, coal mining activities here have brought many economic benefits, created jobs for local people, contributed to promoting the development

of the market economy However, besides that, coal mining has been adversely affecting the surrounding environment In addition to the benefits brought by the coal mining and processing industry to Thai Nguyen province, the current environmental impacts are not small: Land erosion problem, air pollution, environmental pollution land and in particular, water pollution such as lowering the groundwater level, polluting irrigation water sources are increasingly causing frustration among the people Therefore, the assessment of the current water environment in coal mining activities in Thai Nguyen is necessary

Stemming from the above reality, with the guidance of the teachers, I carried out the topic: "Report on assessment of the current state of water environment in coal mining of Khanh Hoa coal mine" to apply the Theoretical knowledge you have learned in school to apply in practice Propose measures to manage and improve wastewater treatment technology for factories to improve environmental quality

1.2 Introduction of Khanh Hoa coal company- VVMI

Figure 1.1: Khanh Hoa Coal company

1.2.1 Geographical location

Khanh Hoa coal mine is 4 km west of Thai Nguyen city center The west

of the mine is adjacent to Ba Son coal mine, the Southeast is adjacent to Quan Trieu station The East of the mine is adjacent to Highway 3 Thai Nguyen - Bac Kan - Tuyen Quang

Adjacent to 3 communes:

+ An Khanh commune (Dai Tu district)

+ Son Cam commune (Phu Luong district)

+ Phuc Ha commune (Thai Nguyen city)

Figure 1.2: Topographic map of Khanh Hoa coal mine

The quarry's infrastructure has been built relatively fully, the communication routes from the quarry to the villages and to the city center are all concrete roads with a roadbed width of> 5m

- To make the fullest use of the reserves in the mines to enrich the country

1.2.4 Organizational structure

Table 1.1: Current number of employees at the mine

1.2.5 Capacity and mine life

The estimated mine capacity is 800,000 tons/year

The expected life span of mine is 25 years (from 2013 to 2037)

- Wastewater management and treatment like?

- What is the impact of coal mine wastewater on the environment and people living around the coal company?

1.4.2 Hypotheses

Null Hypothesis (Ho):

- Water is observed flowing around coal production areas The water quality around the coal company is polluted Water quality parameters are higher than permitted standards

- Liquid waste treatment system at Khanh Hoa coal mine does not operate effectively, wastewater after treatment are not allowed to discharge into the environment

- The surrounding household and surrounding landscape area may be polluted with water due to the factory's production activities

Alternative hypothesis (Ha):

- Although wastewater discharged from coal production areas, the parameters of elements in the country are lower than the permitted level The water quality around the coal mine is safe

- Liquid waste treatment system in Khanh Hoa coal mine operates effectively, wastewater after treatment is allowed to discharge into the environment

- The household area and surrounding landscape are not polluted with water because wastewater is treated efficiently before being discharged into the environment

1.5 Limitations

• Collection and disposal issues

All wastewater generated from the open pit and pit mining area is led to the pit bed, preliminary settling before being pumped to the centralized wastewater treatment station for treatment

Currently, the wastewater collection and treatment of Khanh Hoa Coal Company are relatively stable However, there are still possible problems that affect wastewater treatment such as Failure of equipment, high push height, water quality fluctuations in flow, and concentration

The expansion and increase in the capacity of coal mines in recent years have had a significant impact on the surrounding environment Mining is one of the activities that generate a large amount of wastewater, wastewater from Khanh Hoa coal mine is basically treated through a sedimentation tank using chemical sedimentation, the treated water meets the discharge standards Discharge into surface water The open-pit mine of Khanh Hoa coal mine is currently exploited

at a depth of ≥-225m, greatly affecting the surrounding groundwater level, leading to the risk of lowering the groundwater level

1.6 Definitions

Liquid waste: is all waste that exists as a liquid rather than either a gas or a solid It includes both waste produced as a liquid and waste that has been converted into a liquid for handling

Wastewater: is broken into two categories (gray and black water) Gray water is from showers, baths, whirlpool tubs, washing machines, dishwashers and sinks other than the kitchen sink Black water is from toilets and kitchen sinks

Wastewater treatment: is the process of removing pollutants from waste water such as household, commercial and institutional wastewater It includes physical, chemical, and biological processes to remove pollutants

Sediment tank is a wastewater treatment facility built with a rectangle that allows to store wastewater for a certain period of time in order to allow suspended substances under the effect of gravity to settle to the bottom duty to retain sediment and floating impurities contained in sewage The sedimentation process is influenced by the following factors: wastewater flow, settling time, specific gravity and load calculated by suspended solids, flow velocity in tanks, wastewater temperature and size of settling tanks With high efficiency, simple construction structure, so settling tanks are selected by many plants, especially those with a capacity of more than 20,000 m3 / day

The method of flocculation is to put in water coagulants These substances will neutralize the charge of the water-soluble colloidal particles, preventing the turbulence of the ions to facilitate flocculation For wastewater with high SS content, the flocculation process also has a great effect on flocculation so that the sedimentation process will then remove these deposits, which means a significant reduction of SS amount

PART II LITERATURE REVIEW 2.1 Current status of coal mining environment in Khanh Hoa coal company

2.1.1 Current status of Khanh Hoa coal mine in Thai Nguyen province

Khanh Hoa coal mine is a large coal mine located in Dai Tu district of Thai Nguyen province It was started in 1949 until now and has brought many socio-economic benefits such as increasing budget revenues for the province, coal mining with outdated technology has significantly affected environment, topography and landscape of Thai Nguyen province

2.1.2 The water environment situation due to the operation of the Khanh Hoa coal mine in the province

The expansion and increase in the capacity of coal mines in recent years have had a great impact on the province's environment

The risk of shrinking the area of agricultural land, forestry, reducing biodiversity, changing topography

The risk of lowering the groundwater level: Leaving the pit pits, the pit lines with great depth Khanh Hoa's open-pit mine is now down to a depth of -

230, potentially affecting the groundwater level in the area

Risk of the landslide: High landfills The phenomenon of the landslide in the landfill causes sedimentation of surrounding streams, especially affecting the people's rice fields, causing difficulties in agricultural production

Water pollution: Mineral extraction is one of the types of activities that generate wastewater, the typical pollutant indicator in wastewater is suspended solids, color, some heavy metals, if not treated Thoroughly before being discharged into the environment, there will be a risk of water pollution

General assessment: In addition to bringing about significant economic efficiency in the past years, coal mining has also left many problems that need to

be addressed, such as shrinking land area, decreasing biodiversity, and pollution water, the problem of landfill erosion, stream bed sedimentation To have radical solutions to this problem, it is necessary to have the synchronous attention

of investors and management agencies local authorities and authorities

2.2 Measures to minimize water pollution

2.2.1 Measures for storm water runoff and construction wastewater

In order to ensure that during the construction period, it will not affect the normal production activities of the production units, in the treatment station will

take the following measures:

❖ Measures for construction wastewater drainage:

- According to natural terrain, the direction of water flowing in the WWTP slopes from the gate of the WWTP towards the clean water tank at the end of the station Therefore, the drainage system for construction along the internal road of the WWTP is 76 m long, with the dimensions of 50 x 50 cm At the end point of the construction drainage route, dig a pit with an area of 6m3, with a width of 2 m, length of 3 m and depth of 1 m to settle construction water, then connect to the existing rainwater drainage system for drainage exit to the stream The drainage lines ensure thorough drainage, do not cause flooding during construction and do not affect the ability to drain water to the outside

❖ Measures for rain water drainage:

- Rainwater drainage system around the Station: built around the Station and connected to the storm water drainage system of the Station in use

The construction of the drainage system is also an investment item of the project, so the construction right in this period will significantly contribute to the protection of aquatic ecosystems, the quality of water receiving water Deposed rock and soil are dredged regularly

Figure 2.1 Design principles of drainage ditches and settling manholes

- Regularly check, dredge and clear the building to prevent construction waste from entering the drainage system, causing blockage of the drainage system

- Do not concentrate materials and fuels near and next to the drainage line

to prevent leakage into the sewer line

- Constructional storm water and wastewater drainage routes are carried out in accordance with the regional drainage planning

Effectiveness of the measure:

- The measure is taken for good results Solving the problem of local inundation, not causing pollution of the water and soil environment in the project area The drainage lines ensure thorough drainage, do not cause flooding during construction and do not affect the drainage capacity of areas to the outside, with high feasibility

- Implementation time during construction activities of the station

2.2.2 Measures for domestic wastewater treatment

❖ Mitigation measures:

- According to the design of the project, the amount of labor involved in construction is not large, so use the toilet of the station that was built

- Reasonable organization of human resources in the construction phase

- Regularly inspect and dredge, not to let mud, dirt and garbage enter the sewer drainage To ensure the principle of not obstructing and unhygienic construction activities of the Project as well as not affecting the general drainage system of the area

- Construction workers are strictly forbidden: defecating indiscriminately, causing water pollution and general unsanitary

❖ Effectiveness of the measure:

- The measure is implemented with good results, after being treated domestic wastewater meets standards to allow discharge into the environment

2.3 Environmental monitoring, prevention and response measures

2.3.1 Legal records of environmental protection

a Regarding dossiers of environmental impact assessment and implementation of contents of dossiers of environmental impact assessment

- Environmental impact assessment report and environmental rehabilitation and restoration project of Khanh Hoa open pit mining project (Expanded renovation), approved by the Ministry of Natural Resources and Environment in Decision No 1679 / MONRE dated August 12, 2014;

- The environmental impact assessment report and the environmental rehabilitation and restoration project of the open pit pit pit mining project approved by Thai Nguyen Provincial People's Committee in Decision No 1685 /

PC dated July 17 / 2009;

- Detailed environmental protection project The Khanh Hoa coal mine cleaning system was approved by the People's Committee of Thai Nguyen province in Decision No 392 / PC dated February 21, 2017;

- Certificates of completion of environmental protection works:

+ Open-pit project: Certificate of completion of environmental protection works of Khanh Hoa open-pit mining project No 117 / GXN-TCMT dated November 20, 2015 of Vietnam Environment Administration - Ministry of Natural Resources and Environment

+ Underground tunnel project: Certificate of completion of environmental protection works of the Project of exploiting open pit fringe tunnel No 05 / GXN-STNMT dated March 12, 2018 of the Department of Natural Resources and Environment of Thai Nguyen province

- Periodic environmental pollution control report: Currently the Company carries out periodic environmental monitoring with a frequency of 04 times / year

in accordance with the approved monitoring network

b About hazardous waste management

- Register of hazardous waste source owner issued on March 7, 2019; Code QLCTNH 19.000115.T (4th issue)

c Regarding industrial solid waste management and domestic solid waste

- For solid waste (peeled soil and rock during the mining process): Peeled soil and rock during the exploitation process, be managed and dumped into yards according to the approved planning and design

- Domestic solid waste: The Company collects the entire amount of domestic waste generated in the container to transfer it to the unit having the

function of treating domestic waste

2.3.2 Regarding the current state of the water environment

- Regarding wastewater treatment:

+ Wastewater treatment system: Treatment capacity: 1200 m3 / hour; License for wastewater discharge into water sources No 3483 / GP-BTNMT dated December 28, 2015 of the Ministry of Natural Resources and Environment

+ Treatment technology: Wastewater is forcibly pumped up from under the pits, leading to concrete ditches and culverts and flowing into regulating lakes: Wastewater is treated by technology using polymer A101 deposition chemicals in combination with flocculation causes suspended solids in wastewater before being discharged into the receiving environment

Average generated volume by 2020: ≥ 11,000 m3 / day and night

+ Discharge location: Hamlet 3, Phuc Ha commune, Thai Nguyen city + Source of receiving: Stream Goc Si

+ Quality of treated water: Meets National technical regulation on industrial wastewater VNS 40: 2011 / MONRE, column B

+ Wastewater circulation: Post-treated wastewater is supplied to dust spraying system for dusting in the screening area, coal cleaning and watering system and for dusting road irrigation in the production area

2.3.3 Water environmental protection works and measures

a Wastewater collection and treatment works and measures

Production wastewater generated during the extraction at the pit is pumped to a centralized wastewater treatment station and the Company has hired TKV Environment Co., Ltd to handle it up to the standards before being discharged into the environment Environment-TKV One Member Limited Company, granted License No 3483 / GP-MONRE dated December 28, 2015 by the Ministry of Natural Resources and Environment, is allowed to discharge wastewater into water sources according to regulations with a maximum flow of 28,800 m3 / day and night

b Spraying water on the internal route

- To minimize dust emissions on the transportation route of coal, soil and rock and other transport routes of the Company

- The company regularly carries out watering (using treated wastewater)

on the transportation route outside the mine production boundary (from the security station No 1 to Highway 3) and in the production area with frequency average rate 4 flights / day (09 months dry season); on average 02 flights / day

(03 months in the rainy season) And regularly carry out irrigation in the production field, the landfill

- The company uses 04 specialized water tanks with a tank capacity of 18m3 (CAT vehicles, KPAZ vehicles) to water the mine dust

10 Road level outside the production boundary: 1.82km from station 01 to Quan Trieu market junction and 1.5km from the 6-kiln lime kiln to the Quan Trieu cement-stone gathering yard The total number of watering trips in the year

is about 2,700 trips / year Water for irrigation to reduce dust and mist is partly taken from exploitation pits and reuse of treated wastewater In addition to watering the road to reduce dust outside the production boundary, the Company also incorporates a car wash plan and covers the process of transporting products for consumption

- Along the internal coal transportation route to the screening area The company has a dust-proof misting system and has been in use since 2011

c Plant trees around the premises, along the transportation route, disposal area

In order to protect the environment of the Company's working area and based on actual conditions on the production site, the Company annually grows indigo acacia

2.3.4 Works, measures to treat and minimize environmental impacts from other waste sources

a Treatment measures for storm water runoff

To build a rainwater collection system and orient the flow leading down to an open pit to pump it up to a centralized wastewater treatment station for treatment up

to discharge standards before being discharged into the environment

b Treatment of wastewater containing grease

Wastewater containing a lot of grease and other impurities from the repair and maintenance workshop on the premises +32 after passing through the sedimentation manhole to filter out the raw sediment, it is processed to separate grease by floating oil separator tank and membrane filter to separate grease in wastewater

Figure 2.2: Current mine oil and grease treatment diagram of the mine

Wastewater from car maintenance workshops at +34: wastewater generated from this process is characterized by a lot of grease, metals and other impurities from general mechanized repair Therefore, it is necessary to add an oil filter tank to remove oil in the wastewater before being put into the general treatment system

Wastewater containing grease at the car maintenance workshop at +34 level is not much, only about 10 m3 / day and night Although the volume is small, this wastewater contains a lot of grease and heavy metals, so the company has arranged a gravity-type flotation oil separator tank at this stage The oil particles floating on the surface will be collected, reused or burned

The capacity of the tank is determined by the amount of water stored in the tank is 5 - 10 minutes, the depth of the tank is at least 1m, ensuring the water

Water from Car

wash

Water from the mechanical workshop

Sedimentation gas pit

Oil trap Centralized wastewater

treatment station

flow rate through the tank ≤ 0.005m / s, enough to separate up to 95% of the grease in wastewater

2.4 Environmental monitoring and management program

To minimize negative impacts on the environment and health, evaluate the effectiveness of mitigation measures to sources of impacts The project will develop and implement an environmental management and monitoring program

Proposing an environmental management program of Khanh Hoa wastewater treatment station to expand capacity, based on characteristics of polluting sources and suitable for each phase of the project; select suitable and highly effective technology solutions to manage and treat wastewater during operation Specific measures are as follows:

- Inform relevant organizations and individuals (construction units, workers at treatment stations, .) of regulations and necessary instructions to implement environmental protection in the period construction of wastewater treatment stations

- Manage environmental protection issues during the construction and operation of the WWTP such as: surrounding environment management, waste management and prevention of environmental incidents, organizing the implementation of close to the environment during construction

- Monitoring the implementation of environmental impact mitigation measures, environmental management programs, environmental monitoring programs of units, officers and workers

- Staff and workers station operators have qualifications from intermediate

or higher

- Guide the implementation and inspection of the implementation of the solutions and commitment points stated and approved in the report

- Regularly monitor the impacts of wastewater treatment, fluctuations, report to leaders to propose solutions to prevent, treat and report to environmental authorities district and provincial level The coordinates and parameters of the monitoring points

- Hire a unit with the function of monitoring and measuring in the environmental monitoring program

- Coordinate with local environmental authorities to resolve environmental conflicts between the project and local residents

- The results of analysis and measurement on environmental quality will

be kept for comparison and control, and gathered to periodically send to State agencies with environmental management functions according to regulations

In the Environmental Management Program, the Project Owner commits

to step by step implementing mitigation measures appropriate to each environmental impact, and at the same time with monitoring to control environmental quality This issue demonstrates the corporate responsibility to the community, to the society

Tasks of the project owner's environmental officer:

1 Make an environmental protection plan for each phase of the project operation, annual plan for the Station and submit to the Director for approval

2 Organize the implementation of the environmental protection plan after

it is approved

3 Conduct regular inspection and supervision of environmental issues, safety and environmental incidents of the entire project area

4 Report to the leaders any problems and issues that need to be solved in relation to environmental protection of the Station

5 Manage documents, records, procedures and data related to the environmental protection of the Station

6 Take the lead in monitoring and directing the implementation of environmental protection and signing environmental protection contracts with the concerned units

7 The liaison point with state management agencies on environmental protection, coordination and relationship with local authorities, mass organizations and people on issues related to environment, safety, and trying

• Tasks of relevant departments when conducting wastewater treatment:

- Everyone must fully comply with the rules, procedures and safety rules for each assigned job To use all provided labor protection tools and tools, and neat clothes

- Before working, it is necessary to check the entire workplace, the condition of the equipment, means and working tools, if the occupational safety and sanitation is ensured, before starting the job

- Waste water must be treated to meet the requirements before being discharged into the environment

1 Production Technical Department:

Responsible for issues related to wastewater treatment technology Check the operator that performs the work in the wastewater treatment process, control

the discharge process as well as the quality of the wastewater during discharge, and offer solutions to handle wastewater incidents

Supervising the operator to ensure industrial safety and hygiene, Checking, detecting and handling the mistakes that the unit performs improperly with the wastewater treatment process

2 Control and Consumption Department: is responsible for informing in detail the operating time of the pit drain pump to the management unit, operating the treatment system through daily production orders

3 Department of Electrical Engineering: Setting up measures to install power supply system and install equipment and accessories for the system; Develop a plan for inspection and maintenance at all levels, supervise the implementation of the operation, repair and maintenance process at all levels of the wastewater treatment system

4 Screening Workshop: Manage and operate the wastewater treatment system in accordance with the prescribed process, responsible for the quality of chemical mixing in accordance with the process and norms to ensure the quality

of wastewater eligible for discharge into the environment Check the quality of wastewater daily, decide for daily discharge as well as take all responsibility for water quality when discharging wastewater Manage and use all equipment in the wastewater treatment system after being handed over

PART III RESEARCH METHODS 3.1 Research time and scope

- Time: The study was conducted from April 16, 2020 to October 25, 2020

- Scope of research: Wastewater management at Khanh Hoa coal mine

3.2 Research content

- Assess the current state of wastewater at Khanh Hoa coal mine

- Evaluation of wastewater management and treatment at Khanh Hoa coal mine

- Proposing appropriate solutions to improve the efficiency of wastewater management and treatment at Khanh Hoa coal mine

3.3 Research Methods

3.3.1 Collect key information

Field survey: Wastewater sources at coal mines are observed, photographed, and analyzed sample wastewater to assess the current state of wastewater The system of wastewater collection, treatment, and discharge of wastewater into the environment has also been improved and upgraded

Interview questionnaire: Questionnaire interviewing key officers in charge

of the coal mine environment about the status of coal mine waste management and treatment

3.3.2 Methods of collecting secondary information

Documents, reports on the previous coal mine, and other research reports were collected and studied

3.3.3 Analytical method

The collected information was analyzed, synthesized, tabulated, and mapped

3.3.4 Data processing method

Collected data were processed using Microsoft Excel software

PART IV RESULTS 4.1 Origin of coal mine wastewater

During the operation of coal mines, most wastewater is used for water supply and of course, wastewater will be generated Due to the characteristics of different water-using parts, the discharge capacity of wastewater is not the same However, this difference is not large, so in order to simplify the wastewater collection process and facilitate the design calculation process, people often consider the properties of wastewater generated from coal mine wastewater to be the same

Normally, Khanh Hoa coal mine wastewater arises from the following sources:

- Surface water, underground water flowing into an open pit;

- Wastewater generated from the pit mining area;

- Domestic wastewater generated from the operations of coal mine workers and workers;

4.2 Results of measuring and analyzing wastewater

4.2.1 Results of measuring and analyzing wastewater from mining pits the first phase in 2020

Table 4.1: The results of wastewater analysis from mining pits

No Parameters Unit

Result NTROIW 40:2011/

MONRE (B) NTSX-2.18.1-3