The Department of Biology at the College of Education for Pure Sciences (Ibn Al-Haitham), University of Baghdad, discussed a Master’s thesis entitled “Test ability of Chlorococcum humicola alga for Biotreatment of some ”, submitted by Ibtisam Hussein Mohammed Kadhim under the supervision of Assistant Professor Dr. Thaer Mohammed Ibrahim.
The thesis was examined by a scientific committee comprising:
- Professor Emeritus Dr. Ibrahim Mahdi Azzouz – Chairperson.
- Assistant Professor Dr. Afrah Tuama Khalaf – Member.
- Professor Dr. Buthaina Abdul Aziz Hassan – Member.
- Assistant Professor Dr. Thaer Mohammed Ibrahim – Member and Supervisor.
The research aimed to investigate the potential of algae-based bioremediation for addressing environmental pollution caused by heavy metals. The study examined the physical and chemical characteristics of four selected environmental sites that directly influence algal growth, in addition to identifying and classifying non-diatom algal species present in those locations.
Furthermore, the study involved the isolation, identification, classification, and cultivation of the alga Chlorococcum humicola in a suitable growth medium to evaluate its efficiency in removing heavy metals, including lead, nickel, and chromium, at different concentrations.
The findings highlighted the significance of utilizing microorganisms and natural biological resources in developing sustainable and eco-friendly solutions for environmental remediation. The research contributes to reducing pollution impacts, improving environmental quality, and advancing contemporary applications of environmental biotechnology.
Sustainable Development Goals (SDGs) Supported by the Research:
- SDG 6: Clean Water and Sanitation – through the development of biological methods for reducing heavy metal contamination in water resources.
- SDG 9: Industry, Innovation and Infrastructure – by promoting scientific research and innovation in bioremediation technologies.
- SDG 12: Responsible Consumption and Production – through the adoption of sustainable environmental treatment approaches.
- SDG 15: Life on Land – by supporting ecosystem protection and mitigating the adverse effects of heavy metal pollution.
Four sites were selected along the Tigris River within the reach extending from Al‑Muthanna Bridge to Al‑Doura Bridge to investigate selected non-diatom phytoplankton, physicochemical characteristics, and the pollution levels of certain heavy metal; lead (Pb), nickel (Ni), and chromium (Cr) during October 2024. In addition, the efficiency of the green alga Chlorococcum humicola in the bioremediation of the three detected heavy metals in the waters of the study area was evaluated.
Environmental results revealed slight variations in air temperature among the monitoring sites. The highest mean air temperature was recorded at Al‑Sarafiya Bridge (30.83°C), whereas the lowest was observed at Al‑Kriyat Bridge (22.33°C). Water temperature reached its maximum at Al-Sarafiya Bridge (24.67 °C) and its minimum at Al-Kriyat Bridge and Al-Doura Bridge (20.67 °C). The pH values ranged from 7.60 at Al-Sarafiya Bridge to 7.83 at Al-Doura Bridge. Total dissolved solids (TDS) attained the highest value at Al-Muthanna Bridge (396.33 mg L⁻¹) and the lowest at Al-Kriyat Bridge (260.33 mg L⁻¹). Electrical conductivity (EC) was highest at Al-Sarafiya Bridge (666.33 µS cm⁻¹) and lowest at Al-Kriyat Bridge (547.67 µS cm⁻¹). Sulfate concentrations peaked at the Al-Doura site (246.00 mg L⁻¹) and were lowest at Al-Sarafiya Bridge (118.00 mg L⁻¹). Nitrate concentrations were highest at Al-Sarafiya Bridge and Al-Kriyat Bridge (0.30 mg L⁻¹), while no detectable nitrate was recorded at Al-Muthanna Bridge (0.00 mg L⁻¹). Reactive phosphate (PO₄³⁻) ranged from 0.12 mg L⁻¹ at Al-Muthanna Bridge to 1.06 mg L⁻¹ at Al-Sarafiya Bridge.
Lead concentrations reached a maximum of 572.7 µg L⁻¹ at Al-Kriyat Bridge and a minimum of 209.4 µg L⁻¹ at Al-Sarafiya Bridge. Nickel concentrations were highest at Al-Muthanna Bridge (449 µg L⁻¹) and lowest at Al-Kriyat Bridge (180 µg L⁻¹). Chromium exhibited its highest concentration at Al-Sarafiya Bridge (295.3 µg L⁻¹), whereas the lowest concentration was recorded at the Al-Doura site (76.00 µg L⁻¹).
A total of 28 species of non-diatom phytoplankton were identified in the Tigris River across the four sites. Al-Kriyat Bridge recorded the highest richness (13 species), while the lowest richness (8 species) was observed at both Al-Muthanna Bridge and Al-Sarafiya Bridge. Microscopic examination revealed the presence of Chlorococcum humicola among samples collected from Al-Muthanna Bridge and the Doura Power Station. To obtain sufficient biomass for experimentation, the alga was cultured in BG11 medium under standard laboratory conditions (25 ± 2 °C, light intensity of 3000 lux, 8:16 h light:dark photoperiod, with continuous daily agitation). Based on calculated values, the highest absorbance at a wavelength of 650 nm was recorded on day nine.
Growth rate and doubling time analyses indicated a maximum absorbance-based growth rate of 0.271 and a minimum doubling time of 1.109. Three standard solutions of the heavy metals (Pb, Ni, and Cr) were prepared to assess the bioremediation efficiency of C. humicola by formulating three concentrations (125, 250, and 500 ppm) for each metal using distilled water. Following a 12-day bioremediation period, residual metal concentrations were determined using atomic absorption spectrophotometry (AAS), yielding the following results:
For lead, the highest removal at 125 ppm occurred on day nine (53.6 ppm), whereas at 250 ppm the maximum removal was observed on day six (116.7 ppm). At 500 ppm, the greatest removal occurred on day nine (179 ppm). On the other hand, the results of lead bioremediation showed that the highest removal at a concentration of 125 ppm occurred on day 9, reaching 53.6 ppm. The highest removal at 250 ppm was recorded on day 6, reaching 116.7 ppm, whereas at 500 ppm the maximum removal was 179 ppm on day 9.
In contrast, the results of nickel bioremediation indicated that the highest removal at 125 ppm occurred on day 9, reaching 56.1 ppm. The maximum removal at 250 ppm was observed on day 6, reaching 114.8 ppm, while at 500 ppm the highest removal was recorded on day 12, reaching 148 ppm.
Conversely, chromium bioremediation results showed that at 125 ppm the highest removal occurred on day 9, reaching 63.5 ppm. At 250 ppm, the maximum removal was recorded on day 6, reaching 110.9 ppm, whereas at 500 ppm the highest removal occurred on day 9, reaching 158.2 ppm.
