This study investigates the influence of the initial pH on the removal of reactive black 5 dye (RB5) from water using electrocoagulation (EC) reactor supplied with aluminium electrodes. The influence of the initial pH has been investigated by commencing several sets of continuous flow experiments at five different initial pH values (4, 5, 6, 7, and 8) keeping the current density, inter-electrodes distance, and the concentration of RB5 constant at 2 mA/cm2, 4 mm, and 25 mg/L, respectively. The obtained results showed that the removal efficiency increased gradually as the initial pH increased from 4 to 6 to reach its maximum level (96%) at the neutral range of pH, then it decreased to 74% as the initial pH increased to 8. This change of the removal efficiency with the initial pH could be attributed to the predominant species of aluminium coagulants, where in alkaline and acidic conditions; the prevailing species have low adsorption capacity for pollutants. While, in the neutral range of pH, the predominant species have high adsorption capacity for pollutants.

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9Although Oil and Gas Pipelines (OGPs) are a safe and economical mode of transportation of 10 petroleum products around the world, they face challenges caused by risk factors including 11 safety, security, design, construction and operational risks due to Third Party Disruption (TPD) 12 and acts of terrorism, particularly in developing and unstable countries like Iraq. A lack of 13 knowledge about managing such risks and the scarcity of past data about pipeline failures, are 14 hindering OGP risk management systems. This paper, therefore, focuses on identifying and 15 analyzing the risks caused by TDP in order to develop a holistic Risk Management Model 16 (RMM). A semi-structured questionnaire was designed, using 30 risk factors identified through 17 a comprehensive literature review, distributed to OGP stakeholders in Iraq, via an online survey 18 tool, to collect the research data. SPSS was used to analyze the data and evaluate risk factors 19 which were ranked in order of probability and severity level using a risk index method. A 20 conceptual framework for the RMM is presented, based on the literature review and survey 21 findings. The results reveal that terrorism, sabotage and theft are the most critical safety risks, 22 official corruption and lawlessness the most influential factors for regulatory risks. Pipeline 23 location "Hot-Zones" also have a serious impact on the failure of pipelines. A computer-based 24 risk management model will be developed at the next stage of the study using the RMM and 25 the results of the numerical risk analysis. 26 27 Keywords-Pipelines; risk evaluation; risk management model; safety risk and third-party 28 disruption. 29 2 1. Introduction 30 Oil and gas pipelines (OGPs) are considered a safe and economical mode of petroleum product 31 transportation, however they are subject to a range of hazards and accidental damage that have 32 severe consequences on projects and people's lives. Long-distance pipelines mainly suffer 33 from mechanical, operational and natural hazards [1], design flaws, misuse, corrosion damage 34 and third-party disruption (TPD) [2]. Muhlbauer [3] defines TPD as any individual or group 35 action that obstructs the functionality of the infrastructures' systems in any direct or indirect 36 manner. Peng et al. [4] add any action that accidentally damages OGPs, such as human error, 37 natural phenomena, soil movement (e.g. foundation collapse, landslides, floods and mudslides), 38and surface loads as a result of illegal building, blast construction and live ground loads that 39 compress pipelines. In this paper, TPD refers to all individual and group actions that result in 40 expected or unexpected pipeline damage, at any stage of the pipeline project. At the present 41 time, globally insecure situations are adding more cause for concern and potentially serious 42 consequences to OGP projects. This is especially the case in countries with low levels of 43 security where OGPs often suffer malicious terrorist attacks. Such hazardous environment...

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Currently, there are enormous Risk Factors (RFs) threating the safety of Oil and Gas Pipelines (OGPs) at all stages of projects. However, there is a lack of information about the root causes of pipeline failures and an absence of trusted data about the "probability and severity" levels of the RFs; this hinders the risk management in such projects. To improve the safety level of OGPs, this paper aims to explore stakeholders' perceptions about pipeline failures issues to analyze the RFs and recommend effective Risk Mitigation Methods (RMMs). Due to the lack of trusted data about the RFs and RMMs, this paper started with extensive investigations to identify the critical RFs and the applied RMMs in OGP projects in different circumstances. The findings of these investigations were used to design a questionnaire survey, which was distributed to analyze the "probability and severity" levels of the RFs and evaluate the "usability and effectiveness" degrees of the suggested RMMs. The survey results revealed that RFs related to Third-Party Disruption (TPD) including sabotage and terrorism, corruption and insecure areas are the most severe RFs. Additionally, based on the survey some RMMs such as anti-corrosion efforts, laying the pipelines underground and using technologically advanced risk-monitoring systems were found to be effective RMMs. These results were found to be varied based on the stakeholders' occupation in the projects; for example, the overall survey results indicated that terrorism and sabotage is the most critical RF, while the planners and the researchers identified corruption as the most critical one. It was also observed that using anti-corrosion measures such as isolation and cathodic protection would be the most effective RMM, while the other stakeholders have different perceptions like moving the pipelines underground an advanced risk-monitoring system are the most effective RMMs as indicated by the consultant, planner or designer and researches respectively.