Predictive Design Calculation for the Shejar Wastewater Treatment Plant in the City of Sokna

Abstract

As a result of increased environmental awareness and a genuine interest in protecting the environment from pollution, restrictions on wastewater disposal have increased. This has created a need for wastewater treatment plants before random disposal. Given the importance of these facilities and their enormous construction, operation, and maintenance costs, a design model was developed for the city of Sokna. This model was developed based on a prediction of per capita wastewater consumption of 115 liters/day. The estimated future population density of Sokna is 10,000 people, and the resulting organic load per capita is 50 grams/day. The calculations were completed and the results were acceptable according to existing references for wastewater treatment plant design. The Shagar plant in Sokna is considered one of the modern plants for small residential communities and will serve as a future model for other cities in Libya if it is operational.

Introduction

1. Overview of Sewage and Its Impacts

Sewage is wastewater containing pollutants, microbes, and chemicals, making it unsafe for human use. It originates from households, industries, and runoff, carrying both organic and inorganic substances. If untreated, sewage contaminates groundwater and the environment, posing serious health and ecological threats.

2. Challenges and Need for Treatment

Due to global water scarcity and urban expansion, wastewater treatment is crucial. Issues in Sokna include:

• Poor monitoring and maintenance of treatment plants.

• High temperatures and fluctuating climate conditions.

• Groundwater mixing with sewage due to a high water table.

3. Study Objectives

• Identify treatment plant components.

• Analyze and explain treatment processes.

• Assess performance of the Shejar plant under changing conditions.

4. Literature Review

Since the Industrial Revolution, chemical pollutants have severely damaged ecosystems. Groundwater—Sokna’s main water source—is increasingly polluted and overused. Globally, water pollution and scarcity are worsening, necessitating improved treatment and sustainable use.

5. Sources and Composition of Wastewater

Wastewater is classified into:

• Domestic (from homes, institutions)

• Industrial (from factories)

• Infiltrated water (from broken pipes, groundwater)

• Rainwater
  It contains ~99% water and 1% dissolved/suspended organic and inorganic matter, along with pathogens.

6. Sewerage Network Components

Includes treatment plants, pump stations, main/subsidiary pipelines, manholes, and mills.

7. Study Area: Sokna

Located in Libya’s Al-Jufra region, Sokna has varied topography (mountains, deserts) that affects water flow and infrastructure design. The terrain and winds influence water movement toward adjacent valleys and cities.

8. Shejar Wastewater Treatment Plant

• Located 6 km from Sokna city center.

• Operated since 1999; completed in 2010.

• Uses chlorine for disinfection.

• Designed for 10,000 people, handling 1,000 m³/day.

9. Design and Operational Calculations

Key engineering calculations include:

• Flow Design: 1,000 m³/day (including seepage).

• Sedimentation Basins: Designed for proper settling times.

• Aeration Tank: 1,400 m³ volume calculated based on biological oxygen demand (BOD) removal.

• Sludge Handling:

  • ~168 kg/day of sludge removed.

  • Sludge drying tanks sized at ~306 m² for 30 tons/year of sludge.

Performance metrics (BOD removal, hydraulic/solids loading rates) all meet reference standards, indicating the plant is well within design safety margins.

Conclusion

1) After meeting with the engineers supervising the construction of the Shejar plant and speaking with them at length, it became clear that after treatment, the water is discharged into the valley. This indicates that the project is neither economically feasible nor beneficial to the city of Sokna. 2) In the activated sludge, the obtained barometer values were close to the experimental values, indicating that these results can be used to conduct studies to predict barometers over time. 3) Increasing the number of aeration stages in the activated sludge basin yielded almost the same results, indicating that changing the flow type from full mixing to plug flow does not significantly affect the treatment efficiency. 4) Next to this treatment plant is another wall for discharging recycled water from the drinking water plant at the Shejar internal treatment plant. This will mix the recycled water with the treated wastewater, which is considered one of the company\'s biggest design errors.

References

[1] ZHENG, Chunli, et al. Treatment technologies for organic wastewater. In: Water treatment. IntechOpen, 2013.? [2] PLAPPALLY, A. K., et al. Energy requirements for water production, treatment, end use, reclamation, and disposal. Renewable and Sustainable Energy Reviews, 2012, 16.7: 4818-4848.? [3] NELSON, Kara L.; MURRAY, Ashley. Sanitation for unserved populations: technologies, implementation challenges, and opportunities. Annual Review of Environment and Resources, 2008, 33.1: 119-151.? [4] WINTERS, Matthew S.; KARIM, Abdul Gaffar; MARTAWARDAYA, Berly. Public service provision under conditions of insufficient citizen demand: Insights from the urban sanitation sector in Indonesia. World development, 2014, 60: 31-42.? [5] NELSON, Kara L.; MURRAY, Ashley. Sanitation for unserved populations: technologies, implementation challenges, and opportunities. Annual Review of Environment and Resources, 2008, 33.1: 119-151.? [6] BAINS, William. Many chemistries could be used to build living systems. Astrobiology, 2004, 4.2: 137-167.? [7] JOHNSTONE, Alex H. Teaching of chemistry-logical or psychological?. Chemistry Education Research and Practice, 2000, 1.1: 9-15.? [8] MISHRA, Rakesh Kumar. Fresh water availability and its global challenge. British Journal of Multidisciplinary and Advanced Studies, 2023, 4.3: 1-78.? [9] JACKSON, Robert B., et al. Water in a changing world. Ecological applications, 2001, 11.4: 1027-1045.? [10] GLEESON, Tom, et al. The global volume and distribution of modern groundwater. Nature Geoscience, 2016, 9.2: 161-167.? [11] NEUZIL, Christopher E. Groundwater flow in low?permeability environments. water resources research, 1986, 22.8: 1163-1195.? [12] CARR, Michael H. Formation of Martian flood features by release of water from confined aquifers. Journal of Geophysical Research: Solid Earth, 1979, 84.B6: 2995-3007.? [13] DE LOUW, Perry GB, et al. Rainwater lens dynamics and mixing between infiltrating rainwater and upward saline groundwater seepage beneath a tile-drained agricultural field. Journal of Hydrology, 2013, 501: 133-145.? [14] SHISHAYE, Haile Arefayne; ABDI, Semir. Groundwater exploration for water well site locations using geophysical survey methods. Hydrol. Curr. Res, 2016, 7.1.? [15] DÍAZ-ALCAIDE, Silvia; MARTÍNEZ-SANTOS, Pedro. Advances in groundwater potential mapping. Hydrogeology Journal, 2019, 27.7: 2307-2324.? [16] PANDIT, Aniruddha Bhalchandra; KUMAR, Jyoti Kishen. Drinking water treatment for developing countries: physical, chemical and biological pollutants. Royal Society of Chemistry, 2019.? [17] MOORE, James W.; RAMAMOORTHY, Subramaniam. Heavy metals in natural waters: applied monitoring and impact assessment. Springer Science & Business Media, 2012.? [18] HOWARD, Guy, et al. Domestic water quantity, service level and health. 2020.? [19] PFISTER, Stephan, et al. Projected water consumption in future global agriculture: Scenarios and related impacts. Science of the total environment, 2011, 409.20: 4206-4216.? [20] HOEKSTRA, Arjen Y.; CHAPAGAIN, Ashok K. The water footprints of Morocco and the Netherlands: Global water use as a result of domestic consumption of agricultural commodities. Ecological economics, 2007, 64.1: 143-151.? [21] SONUNE, Amit; GHATE, Rupali. Developments in wastewater treatment methods. Desalination, 2004, 167: 55-63.? [22] TAOURAOUT, A., et al. Hydraulic load rates effect on the performance of Horizontal Multi-Soil-Layering to treat domestic wastewater in rural areas of Morocco. Journal of Materials and Environmental Sciences, 2019, 10.5: 422-430.?

Copyright

Copyright © 2025 Mohamed Abrahem M Arsheda, Masoud Zedan Mbarek, Abobaker G F Ahmeda. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.