2024 Volume 4 Pages 69-74
The Karnaphuli River in Bangladesh, a lifeline for socio-economic activities, plays a crucial role by providing a considerable water supply. However, the aquatic environment is under threat from contamination originating from several sources such as industrial wastewater discharge, maritime operations, wastages from garments and leather industries, fertilizers industries, and the discharge of urban runoff. This study revealed the total petroleum hydrocarbon contamination of the Karnaphuli River. This study delves into the total petroleum hydrocarbon concentrations at several key points along the Karnaphuli River. Near the Amanat Shah Bridge, the total petroleum hydrocarbon level is at 29.70 mg/L, whereas it spikes to 84.67 mg/L in Chaktai Khal, indicating substantial variability across different locations. Mahesh Khal registers a total petroleum hydrocarbon concentration of 52.07 mg/L, followed by 31.09 mg/L in Sadar Ghat, 70.04 mg/L in Khal No 10, and 31.87 mg/L in the KAFCO outfall. These findings illustrate the pervasive nature of total petroleum hydrocarbon contamination throughout the river, thereby posing a grave threat to its ecological integrity and the well-being of communities reliant on it. Comparative analysis with a previous study spanning an 18-year interval unveils a decline in total petroleum hydrocarbon concentrations, hinting at potential improvement in environmental conditions. Although this trend offers a glimmer of hope, it underscores the persistent need for vigilant monitoring and concerted efforts to curtail pollution sources. By elucidating the evolving landscape of total petroleum hydrocarbon contamination in the Karnaphuli River, this study furnishes invaluable insights into its environmental implications and paves a way for informed decision-making in environmental management.
The Karnaphuli River is one of Bangladesh’s most crucial rivers. It originates from Mizoram, India, provides the country’s main port area and flows 27-km long, leaving Chittagong city on its right bank (Hasan et al., 2021). It generated two conspicuous loops: the Dhuliachari and Kaptai. This river plays a substantial role in facilitating the establishment and growth of residential and industrial areas along its banks (Hossen et al., 2019). This river expands the development of several sectors including industrial, agricultural, fishing, household and navigational infrastructure. The Karnaphuli River estuary offers an excellent environment for fish breeding. Owing to its water current and geographical location, it serves as a vital transit channel, supports a range of aquatic ecosystems and provides a source of subsistence for the local inhabitants. By constrast, this estuary has been affected by discharges from several sources because it is located in the catchment area of Chittagong port city, an extensively industrialized area (Majid et al., 2003). According to the Evaluation Approach Paper Project Performance Evaluation Report for Chittagong Port Trade Facilitation Project in Bangladesh (Loan, 2174) (Loan, 2018), around 800 industries are situated on the banks of Karnaphuli, such as Kalurghat, Nashirabad, Sagarica and Anawara. According to the Chittagong Port Authority report, it handled 3,764 ships between 2019 and 2020. The pollution from vessels poses a considerable and grave danger to the Karnaphuli River and Chittagong anchorage region. Chittagong generates a daily waste output of approximately 2,289 tons but only a negligible amount is properly recycled (Masum et al., 2018). The Chittagong City Corporation has been engaging in the disposal of municipal rubbish close to the Patenga sea beach and along the Karnaphuli Shah Amanat Bridge approach road.
The Karnaphuli River is highly exposed to total petroleum hydrocarbon (TPH) from gasoline pumps, spilt oil, chemicals, etc. The contamination of TPHs in water causes several problems for aquatic organisms and humans. TPHs include various chemical compounds originating from crude oil that are subsequently refined to produce various petroleum products. TPH includes jet and diesel fuels, mineral oils, benzene, toluene, ethylbenzene and xylene (BTEX), polycyclic aromatic hydrocarbon (PAH), petroleum products and gasoline components (Kuppusamy et al., 2020). TPH contamination can alter the behavioral pattern of aquatic animals, benthos and microorganisms. Determination of the TPH contamination level in the Karnaphuli River is now of utmost importance for the remediation of TPH contamination in the water. The update of the TPH concentration of the Karnaphuli River water has not been determined since the past few years. It is a comparative study between the present and past TPH concentrations in the water of the Karnaphuli River. TPH concentration in the Karnaphuli River has decreased since the past 18 years. The findings draw the attention of government, regulatory authorities and policymakers, environmental organizations and commercial industries to lessen TPH contamination and reinstate ecological equilibrium in the Karnaphuli River.
This study focuses on the major river Karnaphuli showed in Fig. 1. Water samples were obtained from six substantial outer fall locations (Supplementary material) of the Karnaphuli River, including Near Shah Amanat Bridge (Chaktai-Wapda-Khal), Sadar Ghat, Khal No 10, KAFCO outfall (KAFCO drain), Chaktai Khal and Mahesh Khal.
The samples were collected in October 2023. The grab method was used to collect water samples to examine TPHs at a depth of 0.5 meters below the surface. During the rainy monsoon at high tide, the samples were taken from the bank ±10 m into the river. Samples were taken from six sites using boats. For BTEX/TPH, PAH, and polychlorinated biphenyl (PCB) analysis, 250 mL glass jars with PTFE-lined lids are recommended. However, plastic bottles are also mentioned as an option in the Laboratory Reference Guide (https://rpc.ca/english/pdf/LabRefGuideEN.pdf) (LabRefGuide, 2024). The quality control (QC) of the water sample collection was ensured by thoroughly cleaning the plastic bottles with distilled water, pre-rinsing them with sample water, and promptly storing the collected samples in an icebox to prevent any contamination or degradation before analysis.
Quality assurance and QC for TPH analysis involved several steps to ensure accuracy and reliability of the results. Standardized methods were followed, including using sequential hexane extractions and pH adjustments. Samples were processed under controlled conditions, with emulsions separated by centrifugation and extracts dried using anhydrous sodium sulfate. Gravimetric measurements were taken to constant weight to ensure precision. In addition, calibration of instruments, use of blanks, and duplicate samples were used to validate accuracy and consistency of the analytical results.
ANALYTICAL METHOD FOR TOTAL PETROLEUM HYDROCARBONS CONCENTRATIONBefore starting the extraction process, we visually assessed the water samples and checked their pH levels. We adjusted the pH to below 2 using hydrochloric acid (HCl) to prepare the samples for extraction. Each sample was measured to a volume of 10 mL.
To extract the TPHs, we used a separatory funnel and performed three sequential hexane extractions. For each extraction, we added 50 mL of hexane to 1 L of the water sample (Adeniji et al., 2017). The samples were vigorously shaken for 2 minutes each time to ensure thorough mixing. The first hexane aliquot was used to rinse the sample container to ensure all contents were transferred to the extraction vessel.
After extraction, the solvent extracts were passed through a drying funnel containing anhydrous sodium sulfate to remove any remaining water. These extracts were then combined. During this process, emulsions often formed. To separate large quantities of the extract from the emulsion, we used centrifugation. By adding sodium chloride (NaCl) and spinning the mixture in a centrifuge, the emulsions were effectively broken and separated.
Next, the extract was evaporated at room temperature (approximately 20°C–25°C) to remove most of the solvent. To further remove any remaining water, solvent, and other volatile substances, we heated the extract in an oven at 50°C–60°C for 60 minutes. This step ensures that only the non-volatile TPH residue remains.
To control the moisture effect on the gravimetric determination, the final step involved weighing the TPH residue to a constant weight using a precise 4-place balance. This process ensured that any moisture or volatile components were fully evaporated, providing accurate and reliable measurements of the TPH residue. At the end of the extraction, the total oil and grease content was calculated using the following equation:
After analyzing the water sample of the Karnaphuli River outfalls by gravimetric method the obtained result is shown in Fig. 2.
The six sites were strategically chosen to provide a comprehensive overview of TPH contamination across the Karnaphuli River. The selection criteria included sites representing various pollution sources, geographical spread along the river, proximity to major activities, and availability of historical data for comparative analysis. This comprehensive approach ensures a thorough understanding of TPH contamination and its changes over time.
By carefully selecting these sites, this study aims to provide a detailed and accurate assessment of TPH contamination in the Karnaphuli River, which is crucial for informing effective remediation and sustainable management strategies.
The water samples for this study were collected in October 2023 owing to practical and logistical constraints, including resource limitations and challenges posed by seasonal conditions such as high water levels and strong currents during the rainy season, which can complicate sample collection and compromise safety. Although this single sampling period provides a valuable snapshot of TPH contamination in the Karnaphuli River, it may not fully capture seasonal variations in TPH levels, which can fluctuate owing to changes in water flow, temperature, and pollutant sources. Despite this limitation, the strategic selection of six sampling locations along the river helps in capturing a broad picture of contamination across different areas, highlighting substantial pollution sources and hotspots. The results serve as an indicator of current pollution levels and provide a baseline for future studies, although seasonal sampling and long-term monitoring are recommended to obtain a comprehensive understanding of TPH dynamics and improve the accuracy of the findings. The comparative analysis with historical data indicates a decline in TPH concentrations, suggesting improvements in pollution management practices, yet underscores the need for continued and expanded monitoring efforts for effective and sustainable river environment management.
The standard for TPH in water varies by state; however, many have action levels in the range of 0.1–2 mg/L (Zemo and Foote, 2003), whereas the EU standard limit is of 300 μg/L (Inyang et al., 2018). The United States Environmental Protection Agency’s (EPA) general guideline of 5 mg/L for TPH in water (Udokpoh et al., 2021) is used as a benchmark in this study. This threshold is supported by the EPA’s National Primary Drinking Water Regulations and the Toxicological Profile for TPHs.
The pollution of the Karnaphuli River has been influenced by various factors including the presence of industrial zones, export processing zones, and urban activities. The current investigation suggests the presence of considerable contamination in canals and river water. Owing to the limited number of samples collected, conclusions regarding high TPH concentrations should be interpreted with caution. Chaktai Khal, with a TPH concentration of 84.67 mg/L, appears to be one of the more contaminated locations within the Karnaphuli River. Khal No 10 also shows relatively high pollution levels at 70.04 mg/L. Lower concentrations were observed near Amanat Shah Bridge (29.70 mg/L), KAFCO Outfall (31.87 mg/L), and Sadar Ghat (31.09 mg/L). Mahesh Khal recorded a TPH concentration of 52.07 mg/L, which is higher than that of Sadar Ghat and KAFCO Outfall. These initial findings indicate potential hotspots of contamination; however, more extensive sampling is necessary to confirm these observations and draw definitive conclusions about TPH levels in the river.
However, the critical aspect is that the TPH contamination in the Karnaphuli River has dramatically decreased since the past 18 years compared with the results of Hossain et al. (2005). The previous experiment explored the TPH concentration from the water samples of Chaktai Khal, Mahesh Khal, Khal No 10, and KAFCO Outfall and found 224.71, 71, 338.10, and 53.12 mg/L correspondingly (Hossain et al., 2005). Compared with a previous study (Hossain et al., 2005), the concentration of TPH is decreasing and close to the acceptable value. Two more locations near Amanat Shah Bridge (Chaktai-Wapda-Ferry Ghat) and Mahesh Khal were observed for TPH concentration.
The observed data in Fig. 3 illustrate a considerable reduction in the concentration of TPH in the various outfalls of the Karnaphuli River since the past 18 years. However, the pollution levels in the aforementioned outfall zones are yet to meet the permitted thresholds. Although existing Effluent Treatment Plants (ETPs) have been observed in companies located near the Karnaphuli River, concerns have been raised over their effectiveness and efficiency. Most industrial discharge locations, known as outfalls, along the Karnaphuli River exhibit TPH contamination improvements. The Khal No 10 shows the most notable alterations. In 2005, the recorded level of TPH contamination was 338.16 mg/L, which has subsequently declined to 70.4 mg/L as of November 2023. A considerable transformation took place in the Chaktai Khal. The initial contamination level was recorded as 224.71 mg/L, which subsequently reduced to 84.67 mg/L. The TPH contamination levels in Chaktai Khal, Mahesh Khal, Khal No 10, and KAFCO outfall have experienced changes over the past 18 years. In particular, the TPH contamination levels in these locations are recorded as 140.04, 19.33, 267.76, and 21.5 mg/L correspondingly.
Studies on the Karnaphuli River in Bangladesh report considerable levels of TPH contamination in the river. This finding is comparable with other heavily industrialized or urbanized areas globally, where TPH concentrations often exceed regulatory guidelines (Bhuyan and Islam, 2017; Mukut et al., 2023). For instance, industrial zones in developed countries or regions with intensive petroleum extraction activities often exhibit elevated TPH levels in rivers owing to direct discharge or runoff (Bhuyan and Islam, 2017; Mukut et al., 2023).
Published studies from regions such as North America and Europe report TPH concentrations in the range of 1–100 mg/L in impacted rivers, depending on proximity to industrial sites, oil refineries, and urban centers (Bhuyan and Islam, 2017; Mukut et al., 2023). Similarly, studies from rapidly industrializing regions in Asia and the Middle East may show TPH concentrations exceeding 50 mg/L in heavily polluted water bodies affected by industrial effluents and urban runoff (Bhuyan and Islam, 2017; Mukut et al., 2023). These findings highlight the need for targeted environmental policies and remediation strategies to address TPH contamination and protect river ecosystems worldwide (Bhuyan and Islam, 2017; Mukut et al., 2023).
The comparison underscores the importance of robust environmental regulations and enforcement to mitigate TPH pollution in rivers globally. Areas with stricter environmental standards typically report lower TPH levels in their water bodies than the regions with less stringent regulations (Bhuyan and Islam, 2017; Mukut et al., 2023). Studies on the Karnaphuli River provide valuable insights into TPH contamination levels in a heavily industrialized and urbanized river system, emphasizing the need for urgent remediation efforts to protect the river’s ecosystem and public health (Bhuyan and Islam, 2017; Mukut et al., 2023).
Moreover, the concentration of TPH has decreased over the past 18 years but has yet to meet a permittable value. More attention should be given to reducing TPH pollution, improving the aquatic environment, and saving biodiversity and human health.
Over the past 18 years, considerable efforts have been made to reduce TPH concentrations in rivers. The implementation of strict environmental regulations such as the National Environmental Quality Standards has established specific limits for TPH in industrial effluents. Regular monitoring and enforcement of these regulations have been crucial in reducing TPH discharge. The mandatory installation of ETPs in industries, promoted through government incentives, has been instrumental in treating wastewater before discharge. Relocating heavily polluting industries and upgrading processes to cleaner technologies have further reduced TPH generation. Public awareness campaigns and community participation in river cleanups and monitoring have played crucial roles, with citizens reporting illegal discharges leading to stricter enforcement. Developing green belts and buffer zones along riverbanks has helped filter pollutants, and international collaborations have provided technical and financial support for large-scale pollution control projects. Future recommendations include implementing advanced monitoring systems, updating and enforcing regulations, encouraging sustainable industrial practices, continuing public awareness campaigns, and adopting integrated water resource management approaches. These measures will ensure ongoing water quality improvements and provide a valuable reference for other developing countries.
Owing to industrialization and urbanization, the Karnaphuli River has been polluted for several years. TPH concentration is one of the major contaminations that affects not only aquatic organisms but also humans. This study has described the current situation of TPH contamination in different locations of Karnaphuli River. In 2005, the Karnaphuli River was highly contaminated with TPH. However, this study revealed that the contamination level has decreased from the past 18 years. Government and regulatory authorities have taken some steps that can play a substantial role in reducing TPH contamination. However, this is insufficient. More concern and measures are required to remove TPH. Policy policymakers, environmental organizations, and industries should utilize more methods for addressing the issue to decrease TPH contamination, reinstate ecological equilibrium in the Karnaphuli River, and ensure sustainable management of the environment within its basin.
The authors declare that they have no known competing financial interests or personal relationships that could influence the work reported in this paper.
This material is available on the Website at https://doi.org/10.5985/emcr.20240005.
