Xác định mối nguy hại và đánh giá rủi ro tại xí nghiệp xử lý nước thải dĩ an

TRƯỜNG ĐẠI HỌC THỦ DẦU MỘT KHOA KHOA HỌC QUẢN LÝ *********** BÁO CÁO TỐT NGHIỆP XÁC ĐỊNH MỐI NGUY HẠI VÀ ĐÁNH GIÁ RỦI RO TẠI XÍ NGHIỆP XỬ LÝ NƯỚC THẢI DĨ AN Sinh viên thực : HỒ TỐNG TRỌN Lớp : D17MTSK01 Khoá : 2017 - 2021 Ngành : An tồn sức khỏe mơi trường Giảng viên hướng dẫn : ThS NGUYẾN HIỀN THÂN Bình Dương, tháng 11/2020 TRƯỜNG ĐẠI HỌC THỦ DẦU MỘT TRƯỜNG ĐẠI HỌC THỦ DẦU MỘT KHOA KHOA HỌC QUẢN LÝ KHOA KHOA HỌC QUẢN LÝ *********** BÁO CÁO TỐT NGHIỆP XÁC ĐỊNH MỐI NGUY HẠI VÀ ĐÁNH GIÁ RỦI RO TẠI BÁO CÁO NGHIỆP XÍ NGHIỆP XỬ LÝ TỐT NƯỚC THẢI DĨ AN Giáo viên hướng dẫn Sinh viên thực XÁC ĐỊNH MỐI NGUY HẠI VÀ ĐÁNH GIÁ RỦI RO TẠI (Ký MãTHẢI số SV:DĨ 1724403010050 XÍtên) NGHIỆP XỬ LÝ NƯỚC AN Lớp: D17MTSK01 Giáo viên hướng dẫn Sinh viên thực (Ký tên) Mã số SV: 1724403010050 Lớp: D17MTSK01 ThS NGUYỄN HIỀN THÂN ThS NGUYỄN HIỀN THÂN HỒ TỐNG TRỌN HỒ TỐNG TRỌN Bình Dương, tháng 11 năm 2020 Bình Dương, tháng 11/2020 LỜI CAM ĐOAN Tơi xin cam đoan công trình nghiên cứu riêng hướng dẫn ThS Nguyễn Hiền Thân, Các nội dung nghiên cứu, kết đề tài trung thực chưa công bố bất kì hình thức trước Những số liệu bảng biểu, sơ đồ phân tích đo đạc tơi Ngồi ra, đề tài cịn sử dụng số tài liệu tác giả khác ghi rõ phần tài liệu tham khảo Nếu phát có gian lận tơi xin hoàn toàn chịu trách nhiệm nội dung tiểu luận mình Ngày……tháng……năm…… Hồ Tống Trọn i LỜI CẢM ƠN Được học tập rèn luyện môi trường giáo dục động sáng tạo trường Đại học Thủ Dầu Một niềm hạnh phúc nhiều sinh viên, có thân em Bên cạnh đó, q Thầy Cơ trường cầu nối tri thức tâm huyết với chúng em, người truyền đạt vốn kiến thức quý báu cho chúng em năm học tập trường Đặc biệt em xin gửi lời tri ân tới Thầy Nguyễn Hiền Thân tận tình quan tâm giúp đỡ, hướng dẫn em hoàn thành tốt báo cáo tốt nghiệp Qua thời gian thực tập Chi nhánh Xử lý Nước thải Dĩ An với hướng dẫn tận tình anh Trần Mạnh Giào chị Trương Thị Ái Sương, em có thêm kiến thức kinh nghiệm mà ngồi ghế nhà trường chưa biết Để hoàn thành báo cáo thực tập trước hết em xin chân thành cảm ơn Ban Lãnh Đạo Chi nhánh Xử lý Nước thải Dĩ An tạo điều kiện thuận lợi cho em tìm hiểu thực tiễn suốt trình thực tập công nhà máy Điều cuối phát huy tính tự chủ, phẩm chất đạo đức cơng việc, tính sáng tạo áp dụng trang thiết bị đại vào công việc, kiến thức vững chắc, trình độ chuyên môn cao điều kiện thuận lợi cho sinh viên làm việc sau trường ii TÓM TẮT Nhà máy xử lý nước thải sở hạ tầng vô quan trọng đảm bảo chất lượng sống, nguồn nước sử dụng người, ngồi cịn đảm bảo chất lượng nước cho môi trường tự nhiên Trong trình hoạt động ln tiềm ẩn mối nguy hiểm ảnh hưởng đến sức khỏe công nhân làm việc nhà máy Nghiên cứu thực phương pháp đánh giá rủi ro Bán định lượng để tính toán giá trị rủi ro vận hành nhà máy xử lý nước (WWP) Kết nghiên cứu thu 18 mối nguy tiềm ẩn cao dẫn đến trình xử lý nước Các mối nguy hiểm rò rỉ tháp khử mùi tạo khí thải độc hại vi sinh vật chết có giá trị cao với thang điểm rủi ro 20 điểm - ảnh hưởng thường xuyên đến nhân viên Nghiên cứu xác định mối nguy hiểm có WWP tiền đề để đưa giải pháp giảm thiểu cho vấn đề xảy WWP ABSTRACT The wastewater treatment plant is an extremely important infrastructure to ensure the quality of life, water use of human life, and other ways to ensure water quality for the natural environment In the operation of it, there are always potential hazards affecting the health of the workers working in the factory The study was performed using the Semi-quantitative risk assessment method to calculate the values of operational risks in the water treatment plant (WWP) The results of the study obtained 18 high potential hazards that may lead to the present in the water treatment process The hazards were the leakage of deodorizing towers and the generation of toxic emissions of dead microorganisms that have the highest value with a risk scale of 20 pointsfrequent impacts on employees The study has also identified the dangers present in WWP and this will be the premise for mitigating solutions for problems occurring at its iii MỤC LỤC DANH MỤC BẢNG iv DANH MỤC HÌNH ẢNH vii CHƯƠNG I GIỚI THIỆU 1.1 ĐẶT VẤN ĐỀ viii 1.2 MỤC TIÊU NGHIÊN CỨU 1.2.1 Mục tiêu chung 1.2.3 Phạm vi thực đối tượng thực 1.2.3 Nội dung nghiên cứu 1.2.4 Ý nghĩa đề tài CHƯƠNG II TỔNG QUAN TÀI LIỆU 2.1 TỔNG QUAN VỀ TÌNH HÌNH NGHIÊN CỨU TRONG NƯỚC VÀ NGỒI NƯỚC 2.2 TỔNG QUAN VỀ NHÀ MÁY XỬ LÝ NƯỚC THẢI DĨ AN 2.2.1 Giới thiệu nhà máy Xử lý nước thải Dĩ An 2.2.2 Vị trí địa lý nhà máy 2.2.3 Mục tiêu hoạt động 2.2.4 Phạm vi hoạt động 2.2.5 Công suất hoạt động 2.2.6 Chức nhiệm vụ nhà máy 2.2.7 Mạng lưới thu gom 2.2.8 Chất lượng đầu nước thải 2.2.9 Cơ cấu sơ đồ tổ chức chi nhánh nước thải Dĩ An 2.3 TỔNG QUAN VỀ RỦI RO VÀ SỰ CỐ 2.3.1 Tổng quan loại rủi ro 2.3.2 Tổng quan cố 10 CHƯƠNG III DỮ LIỆU VÀ PHƯƠNG PHÁP NGHIÊN CỨU 12 3.1 TIẾN TRÌNH THỰC HIỆN 12 3.2 DỮ LIỆU NGHIÊN CỨU 13 3.3 NỘI DUNG VÀ PHƯƠNG PHÁP NGHIÊN CỨU 14 3.3.1 Khảo sát đánh giá trạng thu gom xử lý nước thải Xí nghiệp xử lý nước thải sinh hoạt Dĩ An 14 3.3.2 Đánh giá trạng hoạt động diễn nhà máy 14 3.2.3 Kiểm tra giám sát chất lượng nước thải nhà máy 15 3.2.4 Mơ tả rủi ro hậu xảy hệ thống 15 3.2.5 Tính tốn xác định mức độ an tồn hệ thống 15 iv 3.2.6 Đề xuất giải pháp phòng ngừa giảm thiểu cố 20 CHƯƠNG IV MỐI NGUY HẠI VÀ ĐÁNH GIÁ RỦI RO TẠI XÍ NGHIỆP XỬ LÝ NƯỚC THẢI DĨ AN 21 4.1 HIỆN TRẠNG THU GOM VÀ XỬ LÝ NƯỚC THẢI SINH HỌAT DĨ AN 21 4.1.1 Hiện trạng thu gom 21 4.1.2 Hiện trạng hoạt động diễn nhà máy 26 4.1.3 Biến động chất lượng nước sau xử lý hiệu suất hệ thống 38 4.2 XÁC ĐỊNH RỦI RO VÀ ĐỀ XUẤT GIẢI PHÁP 40 4.2.1 Xác định mối nguy hại hệ thống xử lý nước thải 40 4.2.2 Thống kê thông số, xếp hạng cho loại rủi ro 42 4.2.3 Các giải pháp giảm thiểu rủi ro cho hệ thống 44 KẾT LUẬN VÀ KIẾN NGHỊ 50 TÀI LIỆU KHAM KHẢO 52 PHỤ LỤC .A v DANH MỤC BẢNG Bảng 2.1 Quy chuẩn kỹ thuật nước thải đầu nhà máy v Bảng 3.1 Các hạng mục công trình hệ thống xử lý nước thải nhà máy 13 Bảng 3.2 Thang điểm đánh giá tần suất 16 Bảng 3.3 Thang điểm đánh giá mức độ hậu 17 Bảng 3.4 Ma trận đánh giá rủi ro 19 Bảng 3.5 Ma trận rủi ro 20 Bảng 4.1 Phương pháp xử lý nước thải nhà máy Xử lí nước thải Dĩ An22 Bảng 4.2 Thông số bể ASBR 24 Bảng 4.3 Thông số hệ thống đèn UV 33 Bảng 4.4 Thông số bể nén bùn 34 Bảng 4.7 Tình nguy hại tiềm rủi ro liên quan đến hệ thống xử lý nước thải sinh hoạt Dĩ An 40 Bảng 4.8 Giá trị rủi ro tình xảy Xí nghiệp xử lý nước thải Dĩ An 43 Bảng 4.9 Hướng khắc phục cố thực tế nhà máy 45 Bảng 4.10 Các đặc tính hướng phịng ngừa tiếp xúc hóa chất 45 Bảng 4.11 Các văn pháp luật nhà máy cần tuân thủ 49 vi DANH MỤC HÌNH ẢNH Hình 2.1 Cổng nhà máy xử lú nước thải Dĩ An Hình 2.2 Vị trí địa lý chi nhánh xử lý nước thải Dĩ An chụp vệ tinh Hình 2.3 Cơ cấu sơ đồ tổ chức chi nhánh nước thải Dĩ An Hình 3.1 Tiến trình thực 12 Hình 3.2 Xí nghiệp xử lý Nước thải Dĩ An 13 Hình 3.3 Các bước thực phương pháp checklist 14 Hình 3.4 Mơ tả cách thức tính điểm rủi ro 20 Hình 4.1 Sơ đồ xử lý nước thải nhà máy xử lý nước thải Dĩ An 21 Hình 4.2 Nhà bơm 26 Hình 4.3 Song chắn rác thô tự động 27 Hình 4.4 Hệ thống bơm nâng 27 Hình 4.5 Công trình đầu vào 28 Hình 4.6 Thiết bị tách rác trống xoay 28 Hình 4.7 Phễu tách cát 29 Hình 4.8 Bể tách dầu mỡ 29 Hình 4.9 Ngăn phân phối nước 30 Hình 4.10 Bể ASBR 30 Hình 4.11 Thời gian hoạt động chu kì bể ASBR 31 Hình 4.12 Giai đoạn phản ứng 31 Hình 4.13 Mô tả giai đoạn lắng 32 Hình 4.14 Giai đoạn gạn lược 32 Hình 4.15 Hệ thống khử trùng UV hồ ổn định 33 Hình 4.16 Bể nén bùn 35 Hình 4.17 Nhà thiết bị tách nước 36 Hình 4.18 Hóa chất hệ thống xử lý mùi 37 Hình 4.19 Biểu thị thông số đầu nhà máy từ 09/09/2020 – 30/09/2020 40 Hình 4.20 Số lượng mức độ rủi ro mối nguy hại 44 Hình 4.21 Xác suất rủi ro xảy HTXLNTSH Dĩ An 44 vii DANH MỤC CHỮ VIẾT TẮT ASBR : Công nghệ bùn hoạt tính dạng mẻ cải tiến (Advanced Sequencing Batch Reactor) BIWASE : Công ty Cổ phần Nước – Môi trường Bình Dương TCVN : Tiêu chuẩn Việt Nam QCVN : Quy chuẩn Việt Nam BTNMT : Bộ Tài Nguyên Và Môi Trường QCVN 14:2008/BTNMT : Quy chuẩn kĩ thuật quốc gia nước thải công nghiệp SS : Chất rắn lơ lửng TSS : Tổng chất rắn lơ lửng COD : Tổng chất hữu có nước thải BOD : Lượng oxy hòa tan nước cho sinh vật hấp thụ THB : Tuần hoàn bùn HTXLNTSH : Hệ thống xử lý nước thải sinh hoạt SVI : đặc tính của hỗn hợp bùn nước (Sludge Volume Index) MLSS : Mật độ bùn MLVSS : Chất rắn lơ lửng hịa tan dễ bay SV30 : Thể tích bùn lắng sau 30 phút TT : Thông tư NĐ : Nghị định viii Bảng Thông số chất lượng nước thải đầu từ 03/09/2020 đến 09/09/2020 Chỉ tiêu Đơn vị Đầu Đầu vào UV Hiệu QCVN suất xử 14:2008/BTNMT, lý Cột A 6–9 pH - 7,64 7,04 Màu Pt/Co 354 23 93,5 - SS mg/L 160 98,8 50 COD mg/L 188 16 91,5 - BOD5 mg/L 108,4 11 89,9 30 NH4+ mg/L 21,7 100,0 NO3- mg/L 3,5 1,1 68,6 30 Tổng N mg/L 26 84,6 - Tổng P mg/L 6,4 0,5 92,3 Cl- mg/L 45,38 56,72 - KQĐ Coliforms MNP/100ml × 106 300 3.000 Bảng Thông số chất lượng nước thải đầu từ 10/09/2020 đến 16/09/2020 Chỉ tiêu Đơn vị Đầu vào Đầu UV Hiệu QCVN suất xử 14:2008/BTNMT, lý Cột A 6–9 pH - 6,83 6,52 Màu Pt/Co 400 25 93,8 - SS mg/L 156 98,1 50 COD mg/L 168 12 92,9 - BOD5 mg/L 98,4 92,9 30 D NH4+ mg/L 18,5 100,0 NO3- mg/L 4,1 1,6 60,9 30 Tổng N mg/L 22 81,8 - Tổng P mg/L 2,2 1,5 31,8 Cl- mg/L 56,72 45,376 - KQĐ Coliforms MNP/100ml × 106 400 3.000 Bảng Thông số chất lượng nước thải đầu từ 17/09/2020 đến 23/09/2020 Chỉ tiêu Đơn vị Đầu vào Đầu UV Hiệu QCVN suất xử 14:2008/BTNMT, lý Cột A 6–9 pH - 7,86 7,24 Màu Pt/Co 463 22 95,2 - SS mg/L 160 98,1 50 COD mg/L 140 24 82,9 - BOD5 mg/L 80,5 91,3 30 NH4+ mg/L 24,2 0,2 99,2 NO3- mg/L 6,2 3,5 43,6 30 Tổng N mg/L 34 79,4 - Tổng P mg/l 5,1 1,7 66,7 Cl- mg/L 56,72 31,196 - KQĐ Coliforms MNP/100ml 17 × 105 220 E 3.000 Bảng Thông số chất lượng nước thải đầu từ 24/09/2020 đến 30/09/2020 Chỉ tiêu Đơn vị Đầu Đầu vào UV Hiệu QCVN suất xử 14:2008/BTNMT, Cột lý A pH - 6,7 6,8 - 6–9 Màu Pt/Co 336 18 94,6 - SS mgL 160 99,4 50 COD mg/L 156 12 92,3 - BOD5 mg/L 93,6 96,8 30 NH4+ mg/L 13,5 0,11 99,2 NO3- mg/L 2,3 42,5 30 Tổng N mg/L 37 89,2 - Tổng P mg/L 1,3 0,1 92,3 Cl- mg/L 56,7 28,4 - KQĐ Coliforms MNP/100ml × 106 220 F 3.000 Hazard Identification and Risk Assessment in Wastewater Treatment Plant of Di An City By Ho Tong Tron, Nguyen Hien Than* (Thu Dau Mot University) Article Info: Received XX XX, 2020,Accepted XX XX, 2020, Available online XX XX 2020 *Corresponding author: thannh@tdmu.edu.vn ABSTRACT The wastewater treatment plant is an extremely important infrastructure to ensure the quality of life, water use of human life, and other ways to ensure water quality for the natural environment In the operation of it, there are always potential hazards affecting the health of the workers working in the factory The study was performed using the Semi-quantitative risk assessment method to calculate the values of operational risks in the water treatment plant (WWP) The results of the study obtained 18 high potential hazards that may lead to the present in the water treatment process The hazards were the leakage of deodorizing towers and the generation of toxic emissions of dead microorganisms that have the highest value with a risk scale of 20 pointsfrequent impacts on employees The study has also identified the dangers present in WWP and this will be the premise for mitigating solutions for problems occurring at its Keywords: Hazard, Risk Assessment, WasteWater, Di An Introduction Environmental health and safety reflect activities in the plants that directly affect workers' health and occupational safety Works performed directly in the factory intaking to potential hazards that may be physical, chemical, or psychological factors that can lead to workplace failures and related injuries works, which affects the quality of work and the profitability of the organization (Bahn, 2012) Hazard identification (HIRA) is a process of identifying and describing hazards by describing their probability, frequency, and severity and assessing adverse consequences, including potential loss and injury The industry needs to identify hazards and assess associated risks for tolerance on an ongoing basis using risk assessment standards and guidelines (Lim et al., 2012; Ramesh, Prabu, Magibalan, & Senthilkumar, 2017) Risk assessment is a method of systematically identifying and analyzing hazards associated with an activity and establishing the level of risk for each hazard (Lim et al., 2012) Hazards cannot be eliminated, and therefore it is necessary to determine and estimate the extent to which an accidental risk can be prevented quantitatively or qualitatively of the hazard mechanism The wastewater treatment plant is an important infrastructure to ensure human health and the environment In the treatment process, the health and environmental safety aspects need to be addressed (Brown, 1997) High-risk workplaces often become the cause of occupational accidents and illnesses Working in water treatment is considered to be a hazardous job, as workers often work at G high altitudes and are exposed to polluted working environments Occupational safety and health are rarely paid more attention Many managers believe that this job is now somewhat less dangerous, but workers in the WWP are still capable of affecting their health and may be death, especially from exposure to deodorizing chemicals (Brown; Vantarakis et al., 2016) and electrical sources present in there The operations in the wastewater plants are modernized and operate automatically, but in addition to those automatic activities there is always human supervision (Trịnh, 2009; TS, CHÍNH, & ANH) to ensure that those automated operating processes are in place (Rubio, Menéndez, Rubio, Martínez, & Practice, 2005) and at the lowest level of errors, employees must know the operation to ensure safety issues (Rubio et al., 2005) and solve the machine problems (Rubio et al., 2005) In addition to these automated operations, the plant is a more concerning threat than the odor treatment system, where the plant must always use gases such as CO2, SO2, NH3, H2S, CH3-SH, etc and these gases cannot be released to the air Components in the air will react with impurities to create more toxic gases and direct effects on the respiratory such as dizziness, nausea, fainting, and so on (Kilroy, Ebner, Chua, & Venkatasetty, 1985) With workers who have a long-time intake and often work in odor handling positions In the water treatment plant, machines, and equipment with large capacity and continuous operation are also used, so the risk of injury to workers is very high Accidents occurred can be caused by employees' negligence when operating machinery or equipment or due to unsecured working environment conditions Potential hazards often occurred operational defects, chemical exposure, or fatigue at work Currently, Vietnam's economic growth rate is increasing rapidly, industrial parks appear more and more In particular, in key economic zones, the number of industrial parks in this region is extremely dense Binh Duong is a province in the Southern key economic Zones, being 28 industrial parks and industrial zones Therefore, the province's environmental issues are receiving special attention from the authorities In which, Di An city is the South Binh Duong area Di An City is adjacent to Ho Chi Minh City to the south and west, with Dong Nai province to the north and east The city has a total land area of about 60 km2 and a population of about 381,000 people in 2014 (Kỳ, Nguyên, & Hưng, 2019) Twothirds of Di An's population come from the provinces to work in the town's industrial zone (Hạnh & Nguyên, 2019).With the goals of environmental protection and public health, Di An’s domestic wastewater treatment plant located in Binh An Ward, Di An, Binh Duong was put into operation in May 2013 However, the study on the hazard and risk of Di An domestic wastewater treatment plant has not been implemented yet In this paper, hazards and risk assessment at Di An wastewater treatment plant will be identified to provide basic information for avoiding disruption and proposing solutions to work efficiency Data and research methodology Data The data were collected from monitoring data and surveying at Di An wastewater treatment plant in 2020 Parameters were used in this study including pH, chrominance, TSS, COD, BOD 5, NH4+, NO3-, N total, P total, and Cl- with monitoring frequency times/month H The Semi-quantitative risk assessment method (HIRA) The study used the HIRA method (hazard identification and risk assessment) to identify potential hazards in the workplaces in the WTP A variety of work conditions were expected to facilitate workplace safety management and control to minimize the likelihood of occurring accidents Hazard identification and risk assessment using the HIRA can apply as a risk assessment tool that will help identify hazards and estimate the risks associated with each identified hazard This risk assessment tool will identify the potential hazards associated with each task within the management and departments Once a hazard has been identified, the associated risks are estimated and classified At the same time, it also allows us to demonstrate our commitment to a safe workplace We must identify hazards and potential hazards in the workplace so that action can be taken to eliminate or control them(Ebadat, 2010) To eliminate or minimize the risk of injury, illness to workers and damage to properties, equipment, and the environment These are a worksite and work inspection process completed to identify all the hazards inherent to the job or the worksite(Aneziris et al., 2008) The Semi-quantitative risk assessment method To be able to assess the level of risks, and to identify the hidden hazards that exist around the working process, it is the responsibility of the management department to learn a defined system to assess and control the term effective risk The steps include: • Hazard assessment: identifies hazards and potential hazards identify risks and assign (ranks) hazards related to hazards based on likelihood and severity to be There are levels • Control of hazards - control of hazards and hazards associated with hazards • Provide information, education, training, and monitoring of hazards, risks, and controls to employees affected by hazards • Review of the hazard assessment and control process TABLE Description of Likelihood Level (Falakh & Setiani, 2018) Level Frequency Consequence Description ● Minor local injuries (first aid and accident, reportable injuries) ● Property damage less than base level amount Rare Very light ● Minor environmental impact ● Loss of production less than base level amount ● Serious onsite injuries (temporary worker injuries) Unlikely Injured without care ● Moderate environmental impact (clean up or remedy consequences in less than week and no long-term effects on the organism) ● Minor offsite impact (public nuisance to the public - noise, smoke, odor, traffic) ● Permanent paralytic injury or may cause death Possible Injured needs ● Significant environmental impact (clean up or treat less than month and I care small impact on the organism) ● Moderate external effects ● Onsite fatality or less than four permanent disabling worker injuries ● High level of property damage Likely Emergency ● Serious environmental impact (cleaning or remediation takes 3–6 months) ● Significant external effects property damage, short-term health effects for the community ● Multiple onsite fatalities or injuries cause permanent on-site injury Almost certain ● Property damage was high Dead ● Large-scale environmental impact (cleaning up or remedying consequences for more than months) ● Serious external impacts, long-term health effects In the process of surveying and experiencing actual work at the factory, as well as during the preliminary survey of a part of factory employees To be able to know the severity of each hazard is divided into levels ranging from light to death After the scale of the frequency-specific consequences from levels 1-5, the value of the risk will be at a relative level and should be analyzed using the Risk Assessment Matrix displayed in Table (Patil, Nagaraj, & Venkataramu) Risk is expressed in a variety of ways to convey the distribution of risk across the factory and the workplace In this work, risk was calculated using the following formula and Table Risk (R) = Frequency (X) x Consequence (Y) Eq (Ramesh et al., 2017) The risk identification phase is essential, as it lays the foundations of risk analysis Therefore, risk identification data will be a prerequisite for the assessment to obtain the best results (Schneider & Beblo, 2010) TABLE Risk assessment matrix (Falakh & Setiani, 2018) Frequency Rare Unlikely Possible Likely Almost certain Very light Injured without care 10 Injured needs care 12 15 Emergency 12 16 20 Dead 10 15 20 25 Consequence From the consequence and frequency scales, we calculated the risk level The level of impact was divided into four levels enclosing low risk, medium risk, high risk and extreme risk respective value [13; 4-6; 8-12; 15-25] (Table 4) J Practical survey method: Observing, taking pictures, and operating Di An Wastewater Treatment Plant (Wastewater Treatment Area) to record the potential hazard and essential information of workers, unintended incidents and problems that the WTP deals with TABLE Risk scale for the WWP Level Risk value Extreme risk 15-25 High risk 8-12 Medium Risk 4-6 Low risk 1-3 Methods of determining hazards After observing and determining hazards and risks at Di An Wastewater Treatment Enterprise, the hazards are identified through the method of the checklist and work analysis The analytical procedure is outlined as follows Checklist Identify hazards Work analysis Hazard analysis Frequency Consequence Risk Figure The scheme of Hazard determining Results and discussion The state of wastewater collection and treatment at Di An wastewater treatment plant Di An wastewater treatment plant has been operating with a capacity of 20000 m3/day and is expected to expand capacity by 2030 to 60,000 m3/day with the current collection network as the drainage systems, separate wastewater (rainwater separate), collected directly (no need through the septic tank) Wastewater collection network includes a pipeline and drainage system with a total length of over 300km with 23,000 connection boxes and households to collect and transport wastewater to treatment facilities K Wastewater from drainage households in Di An city follows the main pipeline flowing to the pumping station Then, wastewater is led to the pump pit and pumped to the inlet at a height enough for wastewater to flow through the plant by itself and after treated wastewater releases to the receiving source, Cai Cau canal, which flows into Dong Nai River Rotary drum filter is installed to remove materials larger than 3mm, waste is automatically collected in the container and disposed of periodically Then, the wastewater flows itself through the rotating sand settling tank, with the continuous rotation of the mixer, the sand (gravel) will be collected at the center of the sand settling tank and then deposited into the sand collection hopper The lifting gas pump system will collect sand (gravel) which will be collected and disposed of periodically, and wastewater continues to flow through the grease separation tank Oil and grease are collected by pumping floating scum and discarded periodically Garbage, sand, and scum, after being separated, will be transported to the Waste Treatment Plant for treatment Wastewater, after being preliminarily treated, will go to the water distribution compartment so that the wastewater flow is evenly distributed to ASBR tanks The most of the pollutants in the wastewater are removed by a biological process that takes place in the ASBR tank Wastewater after treatment at ASBR tank is a decanter with Decanter device and self-flowing through a pipeline through a UV sterilizer with a wavelength of 254 nm in a few seconds to destroy microorganisms in water before discharging to the receiving source The treated wastewater reaches column A, QCVN 14:2008/BTNMT and is discharged into the Cai Cau canal, which flows into Dong Nai river Water quality at the plant is being operated and gives very good treatment efficiency and is expressed as follows: L 10 6.17 6.99 6.32 21 pH QCVN 14 T Output 29/10/2019 pH parameters 9/10/2019 Chrominance – b) Output chrominance parameters 9/10/2019 – 29/10/2019 50 40 30 mg/l mg/l 19 17 a) 20 SS 2 QCVN 14 35 30 25 20 15 10 2.8 SS parameters 9/10/2019 14 12 12 10 12 12 10 COD – d) Output COD parameters 9/10/2019 – 29/10/2019 7.8 mg/l c) Output 29/10/2019 mg/l 19 18 10 20 20 19 QCVN 14 D 22 22 6.79 mg/l mg/l 23 BOD5 6.5 2.1 1.8 QCVN 14 0.3 0.1 e) Output BOD5 parameters 9/10/2019 – f) Output NH4+ 29/10/2019 29/10/2019 M NH4+ 0.3 parameters 9/10/2019 – mg/l g) Output 29/10/2019 0.9 12 10 10 mg/l NO31.5 1.4 1.7 QCVN 14 Total N NO3- parameters 9/10/2019 – h) Output total N parameters 9/10/2019 – 29/10/2019 6.5 mg/l mg/l 30 25 20 15 10 2.6 Total P 0.3 0.1 QCVN 14 90 80 70 57 60 50 40 30 20 10 j) Output total P parameters 9/10/2019 – k) Output 29/10/2019 29/10/2019 79 79 57 Cl- Cl- parameters 9/10/2019 – Figure Wastewater quality parameters after treatment in October 2019 As you can see from Figure the quality of cashew water is within the prescribed range of regulations on domestic wastewater treatment QCVN 14:2008/BTNMT However, we saw that the total P concentration on October 16, 2019, is 6.5 ml/g compared to the allowable limit of 6.0, which is more than 0.5 The excess is insignificant as it was stabilized the next day with a specific index of 0.3, so it showed that the wastewater treatment system at the factory has very good treatment efficiency Determination of hazards of the wastewater treatment system As we can see that the treatment capacity of 20000 m3/day is an extremely large number and must always be in continuous operation so the risks that may occur in the plant will cause a huge impact Moreover, sub-activities supported to the operating plant such as chemical, equipment and emission gas from the treatment system also existed some hazard for employee’s health and environment N TABLE Hazardous and potential risks related to Di An wastewater treatment plant Workplace Hazardous situation Risk potential Wastewater treatment system: Work often at altitude, noise, odor Falls falls, occupational deafness, respiratory diseases, - Rotation of the filter coarse crystals The air blowing devices in the ASBR tank were damaged The quality of treated water is not satisfactory - Slitting, stirring and pumping at ASBR tank The sludge pump was damaged Environmental effects Interrupt the handling operation Noise generation Occupational deafness, health effects Mud pressing Risks due to the carelessness of workers Labor accident Prolonged exposure to the smell of sludge can lead to health problems The odor of sludge arises Mud storage area Health effect Generating foul odor due to death microorganisms Environmental effects The concentration of exhaust gas does not meet the prescribed standards Out of deodorant chemicals Leaks in deodorant chemicals - Sulfuric acid ( H2SO4) to remove NH3 Causing acute poisoning to workers The gas line leaks Spreading H2S emissions into the surrounding environment, increasing H2S, poisoning, causing environmental pollution The defective exhaust fan system The processing system does not function well, reducing the processing efficiency Odor treatment system The treatment system did enclosed to national standard Control room Laboratory Polluting the air - NaOH and NaOCl to remove H2S and CH3SH Power failure, electric leakage, short circuit Electrical leakage from machinery Contaminate the surrounding environment Reduces air quality Health effects, economic damage Health effects, property damage, and health Environmental effects Chemical leaks Health effect Water inlet overload The wastewater does not disinfect and clean residual bacteria in the wastewater Excess muscle excess specified Poisoning the system of receiving water is the Saigon River House sterilization Each process has different operations, thus any carelessness and an equipment failure at the plant also led to the risk causing injuries and certain consequences, affecting workers' health and equipment in the factory from chemical and releasing odor O Assessment of safety risk characteristics Through the risk assessment matrix, it can be seen that the Di An wastewater treatment plant includes 18 hidden hazards in the operating wastewater treatment system and auxiliary works The most hazard problems that arise in the risk assessment can be most clearly seen as problems with fire and explosion due to system overload or short circuit caused by industrial pumps with high capacity and reduction systems Factory odor always leaks chemicals (NH3, H2S, CH3-SH) in the deodorizing process The leakage of deodorant and the risk of fire and explosion are the risks that have a great impact on the health of workers and the efficiency of the plant's treatment The odor is unavoidable and these gases absorb through the eyes, causing burning or discomfort, burning eyes, unconsciousness, redness, and watery eyes A large number of chemicals in the air can cause severe burns, pain, and blurred vision Therefore, warehouse workers must conduct carefully scheduled inspections so that the presence of gases (NH3, H2S, CH3-SH) can be safely controlled, in addition to an emergency management control system that refers to exhaust gas leaks and industrial fires, efforts should be made to prevent known potential hazards TABLE The level of risk in Di An wastewater treatment plant No Hazardous situation Frequency Consequence Risk value (X) (Y) (R) Work at height 15 Working in environmental noise 5 Working in environmental odor 5 The air blowing device in the ASBR tank is damaged 5 The sludge pump is damaged 5 The pump generates noise 15 Toxic emissions are generated after the death of microorganisms 20 Out of deodorant chemicals Leaks in deodorant chemicals 20 10 The gas line leaks 4 11 The defective exhaust fan system 4 12 Power failure, electric leakage, short circuit 10 13 Electrical leakage from machinery 14 Laboratory chemical leaks 12 15 Water inlet overload 12 16 Work in wet conditions 3 17 Manual work at the factory 5 18 Exposure to ultraviolet radiation (UV lamp) 10 P The semi-quantitative (HIRA) identified all the risks in the plant and described the danger level for each risk There were four hazards at extreme risk including work at height, the pump generates noise, Toxic emissions and leaking in deodorant chemicals Six aspects were recorded at high risk such as Out of deodorant chemicals; power failure, electric leakage, short circuit; electrical leakage from machinery; laboratory chemical leaks; water inlet overload and exposure to ultraviolet radiation The medium risk of hazards were working in environmental noise, odor, impaired pump, air blowing device in the ASBR tank, gas line leaks, defective exhaust fan system and manual work at the factory (Table and Figure 5) There is only low risk obtained at the work in wet conditions Overall, Di An wastewater treatment plant existed in a variety of potential hazards that were record high risk Therefore, training activities and equipping personal protection equipment need to be implemented rapidly Besides, prevention of risks from chemical leakage and gas emission affecting employees must be bustled to minimize consequences to health 7 6% 22% Hazards 39% 33% 1 Low risk Medium High risk Extreme risk risk Figure Recapitulation of the risk value Low risk Medium Risk High risk Extreme risk Figure The perception of risk level at Di An water treatment plant It can be seen Figure and Figure the probability occured in low risk accounts for 6%, medium risk 39%, high risk 33%, and extreme risk 22% of all activities that take place in the plant Conclusion Di An wastewater treatment plant with a treatment capacity of 20.000m3 always has to face a large source of waste components in the daily activities of the households in the Di An city Safety risks always exist during the operation of the wastewater treatment system The semi-quantitative HIRA method is used to assess hazards from operating wastewater treatment system showed that the factory has 18 risks, of which have extreme risk - affecting the health of workers, accounting for 22% of the total risks at the factory, aspects were high risk with accounts for 33%, medium risk hazards at 39% and low risk at 6% only one factor Health and safety risks presented in the plant may happen at any time and may cause unfortunate incidents, so it is necessary to have more attention of the leadership department to prevent these hazards Q Acknowledgements This work is supported by Dong Nai Department of Natural Resources and Environment The authors are grateful for editors and anonymous reviewers for 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đánh giá rủi ro giúp xác định mối nguy ước tính rủi ro liên quan đến mỗi mối nguy xác định Công cụ đánh giá rủi ro xác định nguy xảy liên quan đến... 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