INTRODUCTION
Research rationale
Natural resources, including forests, animals, plants, minerals, water, oil, and gas, are vital material assets found in nature that support human life These resources play a crucial role in the environment and are interconnected with it While they offer numerous benefits, irresponsible exploitation and ineffective management have resulted in significant loss and waste of natural resources, particularly in Vietnam.
In the context of integration and development, the mining and mineral processing industry, particularly coal mining, has garnered significant investment interest due to its vital role in supplying fuel for various sectors, including thermal power, cement, and metallurgy As the demand for coal continues to rise, coal mining and processing activities are on the increase However, while the coal mining industry offers substantial economic benefits, it also leads to the depletion of non-renewable coal reserves and poses environmental challenges Therefore, it is essential for investors to implement effective management, technological, and treatment solutions to mitigate the negative environmental impacts associated with coal mining.
Thai Nguyen province is rich in coal reserves, featuring significant mines like Khanh Hoa, Phan Me, and Nui Hong The Khanh Hoa coal mine, located in the northern part of Thai Nguyen city, has historically contributed to the local economy by creating jobs and fostering market development However, the environmental consequences of coal mining are becoming increasingly concerning, including land erosion, air pollution, and water contamination, which affects groundwater levels and irrigation sources These issues have led to growing frustration among residents, highlighting the urgent need for a comprehensive assessment of the water environment related to coal mining activities in Thai Nguyen.
Guided by my teachers, I conducted a report on the assessment of the water environment in the Khanh Hoa coal mine This project allowed me to apply theoretical knowledge from my studies to practical situations I proposed measures to enhance wastewater treatment technology in factories, aiming to improve overall environmental quality.
Introduction of Khanh Hoa coal company- VVMI
The Khanh Hoa coal mine is located 4 km west of the center of Thai Nguyen city It borders the Ba Son coal mine to the west and Quan Trieu station to the southeast, while Highway 3, connecting Thai Nguyen to Bac Kan and Tuyen Quang, lies to the east of the mine.
+ 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 is equipped with a well-developed infrastructure, featuring concrete roads that connect it to nearby villages and the city center, all with a roadbed width of over 5 meters.
Open-pit mining and underground mining, in which open-pit mining is the main type
Figure 1.3: Open-pit mining At Khanh Hoa coal mine
- Meeting coal consumption demand for coal consumers in Thai Nguyen province, especially supplying coal for thermal power plants of An Khanh and Cao Ngan
- To make the fullest use of the reserves in the mines to enrich the country
Table 1.1: Current number of employees at the mine
The company's organizational structure includes: 1 director, 3 deputy directors Departments: 9 departments
The estimated mine capacity is 800,000 tons/year
The expected life span of mine is 25 years (from 2013 to 2037)
Research’s objectives
- Determine the source of generation and main components in the wastewater of Khanh Hoa coal mine
- Assess the status of management and wastewater treatment of Khanh Hoa coal mine
- Some solutions to improve the efficiency of wastewater management and treatment to contribute to environmental protection.
Research questions and hypotheses
The current situation of wastewater management in the Khanh Hoa coal mine reveals significant challenges in ensuring environmental safety An evaluation of the liquid waste treatment system highlights its effectiveness in mitigating the impact of coal mining on both internal and surrounding water environments It is crucial to enhance these systems to protect local water resources and maintain ecological balance in the region.
- Wastewater management and treatment like?
- What is the impact of coal mine wastewater on the environment and people living around the coal company?
- 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
- 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.
Limitations
All wastewater produced from the open pit and pit mining areas is directed to the pit bed for initial settling before being pumped to a centralized wastewater treatment facility for processing.
The wastewater collection and treatment system at Khanh Hoa Coal Company is currently stable, yet potential issues remain that could impact its effectiveness These challenges include equipment failures, high push heights, and fluctuations in water quality and concentration.
The recent expansion of coal mines, particularly the Khanh Hoa coal mine, has significantly impacted the surrounding environment Mining operations generate substantial amounts of wastewater, which is treated through a chemical sedimentation process in sedimentation tanks The treated water meets discharge standards before being released into surface water However, the open-pit mining at depths of ≥-225m poses a risk to the surrounding groundwater levels, potentially leading to a decrease in groundwater availability.
Definitions
Liquid waste refers to any waste material that exists in a liquid state, distinguishing it from solid or gas forms This category encompasses waste generated in liquid form as well as waste that has been transformed into a liquid for easier management.
Wastewater is classified into two main categories: gray water and black water Gray water originates from sources such as showers, baths, whirlpool tubs, washing machines, dishwashers, and sinks (excluding kitchen sinks) In contrast, black water is generated 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
A sediment tank is a rectangular wastewater treatment facility designed to store wastewater for a specific duration, allowing suspended solids to settle to the bottom under gravity This process effectively retains sediment and floating impurities from sewage Key factors influencing sedimentation include wastewater flow, settling time, specific gravity of suspended solids, flow velocity, wastewater temperature, and the size of the settling tanks Due to their high efficiency and straightforward construction, sediment tanks are commonly chosen by many plants, particularly those with capacities exceeding 20,000 m³ per day.
Flocculation is a process that involves adding coagulants to water, which neutralizes the charge of water-soluble colloidal particles and reduces ion turbulence, thereby promoting flocculation This method is particularly effective for wastewater with high suspended solids (SS) content, as it enhances sedimentation, leading to a significant reduction in SS levels.
LITERATURE REVIEW
Current status of coal mining environment in Khanh Hoa coal
2.1.1 Current status of Khanh Hoa coal mine in Thai Nguyen province
The Khanh Hoa coal mine, situated in the Dai Tu district of Thai Nguyen province, has been operational since 1949, contributing significantly to the region's socio-economic development by boosting budget revenues However, the use of outdated coal mining technology has had a detrimental impact on the 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
High landfills pose a significant risk of landslides, leading to sedimentation in nearby streams This phenomenon adversely impacts local rice fields, creating challenges for agricultural production.
Mineral extraction activities generate wastewater that often contains pollutants such as suspended solids, color, and heavy metals If this wastewater is not properly treated before being released into the environment, it poses a significant risk of water pollution.
Coal mining has historically contributed to economic efficiency, but it has also resulted in critical issues such as reduced land area, loss of biodiversity, water pollution, landfill erosion, and stream bed sedimentation Addressing these challenges requires a coordinated effort from investors, local authorities, and management agencies to implement effective and sustainable solutions.
Measures to minimize water pollution
2.2.1 Measures for storm water runoff and construction wastewater
To minimize disruption to the normal operations of production units during construction, the treatment station will implement specific measures.
❖ Measures for construction wastewater drainage:
The water flow direction in the Wastewater Treatment Plant (WWTP) follows the natural terrain, moving from the entrance towards the clean water tank The construction drainage system along the internal road measures 76 meters in length and has dimensions of 50 x 50 cm At the end of this drainage route, a pit measuring 6m³—2 meters wide, 3 meters long, and 1 meter deep—will be excavated to collect construction water, which will then connect to the existing rainwater drainage system for discharge into the stream This drainage setup is designed to ensure efficient water removal, preventing flooding during construction while maintaining the effectiveness of external water drainage.
❖ Measures for rain water drainage:
- Rainwater drainage system around the Station: built around the Station
The construction of the drainage system is a crucial investment for the project, playing a vital role in safeguarding aquatic ecosystems and enhancing the quality of receiving water Regular dredging of deposited rock and soil is essential to maintain optimal functionality and environmental health.
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
This measure, though costly, has a long-term effect, is easy to deploy, has economic efficiency and meets the requirements of environmental protection
- The construction and operation of the treatment system will increase investment costs
The initiative aims to achieve effective results by addressing local inundation issues while preventing pollution of water and soil in the project area The drainage systems are designed for efficient water management, ensuring no flooding occurs during construction and maintaining the drainage capacity of surrounding areas, demonstrating high feasibility.
- Implementation time during construction activities of the station
2.2.2 Measures for domestic wastewater treatment
- 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
Regular inspections and dredging are essential to prevent mud, dirt, and debris from entering the sewer drainage system This practice ensures that construction activities remain unobstructed and hygienic, while also protecting the overall drainage system of the area.
- Construction workers are strictly forbidden: defecating indiscriminately, causing water pollution and general unsanitary
- The measure is implemented with good results, after being treated domestic wastewater meets standards to allow discharge into the environment.
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
The environmental impact assessment report for the Khanh Hoa open pit mining project, along with its environmental rehabilitation and restoration plan, was approved by the Ministry of Natural Resources and Environment under Decision No 1679/MONRE on August 12, 2014.
The Thai Nguyen Provincial People's Committee has approved the environmental impact assessment report and the environmental rehabilitation and restoration project for the open pit mining project, as outlined in Decision No 1685.
- 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:
The Khanh Hoa open-pit mining project, identified by certificate No 117 / GXN-TCMT, received its completion certificate for environmental protection works from the Vietnam Environment Administration under the Ministry of Natural Resources and Environment on November 20, 2015.
The underground tunnel project has received a Certificate of Completion for its environmental protection works, as issued by the Department of Natural Resources and Environment of Thai Nguyen province This certification, dated March 12, 2018, pertains to the exploitation of open pit fringe tunnel No 05, ensuring compliance with environmental standards.
- 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
During the mining process, solid waste, including peeled soil and rock, must be managed and disposed of in designated areas according to approved planning and design guidelines.
- 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
+ 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
Wastewater is pumped from pits into concrete ditches and culverts, flowing into regulating lakes The treatment process utilizes polymer A101 deposition chemicals alongside flocculation to remove suspended solids from the wastewater before it is discharged into the environment.
+ 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
Post-treated wastewater is utilized in a dust spraying system for effective dust control in the screening area, enhances coal cleaning processes, and is employed for road irrigation in the production area.
2.3.3 Water environmental protection works and measures a Wastewater collection and treatment works and measures
During the extraction process at the pit, production wastewater is pumped to a centralized treatment facility, where TKV Environment Co., Ltd ensures it meets environmental standards before discharge The company operates under License No 3483/GP-MONRE, issued by the Ministry of Natural Resources and Environment on December 28, 2015, permitting a maximum discharge of 28,800 m³ per day and night into water sources Additionally, water is sprayed on internal routes to manage dust and maintain site conditions.
- To minimize dust emissions on the transportation route of coal, soil and rock and other transport routes of the Company
The company implements regular watering using treated wastewater along the transportation route outside the mine production boundary, specifically from security station No 1 to Highway 3 During the nine-month dry season, this process occurs at an average frequency of four times per day, while in other periods, it averages two times per 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 10- 18m3 (CAT vehicles, KPAZ vehicles) to water the mine dust
The road outside the production boundary extends 1.82 km from station 01 to the Quan Trieu market junction and 1.5 km from the 6-kiln lime kiln to the Quan Trieu cement-stone gathering yard Annually, the company undertakes approximately 2,700 watering trips to mitigate dust and mist, utilizing water sourced from exploitation pits and treated wastewater In addition to regular road watering, the company has implemented a car wash plan and ensures proper covering during the transportation of products for consumption.
Since 2011, the company has implemented a dust-proof misting system along the internal coal transportation route to the screening area Additionally, efforts to enhance the environment include planting trees around the premises, along the transportation route, and in the 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 establish an effective rainwater collection system, direct the flow towards an open pit, which will facilitate the pumping of collected water to a centralized wastewater treatment facility This system is essential for treating wastewater that contains grease, ensuring proper management and environmental safety.
Wastewater from the repair and maintenance workshop, which contains significant amounts of grease and impurities, undergoes treatment after passing through a sedimentation manhole to remove raw sediment The process continues with a floating oil separator tank and a membrane filter, effectively separating grease from the wastewater.
Figure 2.2: Current mine oil and grease treatment diagram of the mine
Wastewater generated from car maintenance workshops is often contaminated with grease, metals, and various impurities due to mechanized repairs To effectively manage this pollution, it is essential to incorporate an oil filter tank that removes oil from the wastewater prior to its entry into the general treatment system.
The car maintenance workshop generates approximately 10 m³ of wastewater daily, which, despite its small volume, is heavily contaminated with grease and heavy metals To effectively manage this waste, the company has installed a gravity-type flotation oil separator tank, allowing for the collection and reuse or incineration of the oil particles that float to the surface.
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 the mechanical workshop
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.
Environmental monitoring and management program
To reduce environmental and health risks, it is essential to assess the effectiveness of mitigation measures addressing sources of impact The project will establish and execute a comprehensive environmental management and monitoring program.
The proposed environmental management program for the Khanh Hoa wastewater treatment station aims to enhance its capacity by addressing the specific characteristics of pollution sources and tailoring strategies for each project phase This initiative focuses on selecting effective technology solutions for efficient wastewater management and treatment throughout the operational process.
- 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
Effective management of environmental protection is crucial during the construction and operation of wastewater treatment plants (WWTPs) This includes overseeing the surrounding environment, implementing robust waste management practices, preventing environmental incidents, and ensuring that construction activities are conducted with minimal impact on the environment.
- 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
- Guide the implementation and inspection of the implementation of the solutions and commitment points stated and approved in the report
Regular monitoring of wastewater treatment impacts is essential to identify fluctuations and effectively report findings to leadership This proactive approach enables the proposal of solutions for prevention and treatment, ensuring compliance with environmental regulations It is crucial to maintain accurate coordinates and parameters for monitoring points to facilitate thorough reporting to district and provincial environmental authorities.
- 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
Analysis and measurement results of environmental quality will be maintained for comparison and control purposes, and will be regularly compiled and submitted to state agencies responsible for environmental management, in accordance with established regulations.
The Environmental Management Program reflects the Project Owner's commitment to systematically implement mitigation measures tailored to each environmental impact, while also ensuring continuous monitoring to maintain environmental quality This approach underscores the company's dedication to corporate responsibility towards the community and society as a whole.
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 beginning any work, it is essential to thoroughly inspect the entire workplace, including the condition of equipment, tools, and safety measures, to ensure that occupational safety and sanitation standards are met.
- Waste water must be treated to meet the requirements before being discharged into the environment
Responsible for issues related to wastewater treatment technology Check 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.
RESEARCH METHODS
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
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
Research Methods
A field survey was conducted to examine wastewater sources at coal mines, involving observation, photography, and analysis of wastewater samples to evaluate their current condition Additionally, enhancements have been made to the systems for collecting, treating, and discharging wastewater into the environment, ensuring improved management and compliance with environmental standards.
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
The collected information was analyzed, synthesized, tabulated, and mapped
RESULTS AND DISCUSSION
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
Sourse: The environmental engineering department of Khanh Hoa coal company
- The value after the "