Environmental Engineering Department at the College of Engineering, University of Baghdad, held PhD dissertation examination titled:
“Decontamination of Dyes and Bisphenol-A from Wastewater using Immobilized Plant Enzyme”
By the student Waam Abd AlWahab Muhammed and supervised Prof.Dr.Muhanned Jasim Muhammed Ridha on Wedenesday 10/7/2024, in the Environmental Engineering discussion hall. The examination committee consisted of Prof.Dr. Shahla Ismail Ibrahim as Chairman, and the membership of Prof.Dr.Abeer Ibrahim Musa, Prof.Dr. Khalid Khazaal Hummadi, Prof.Dr. Zyad Tariq AbdAli, and Assist.Prof.Dr. Wasam Hasan Alwan. After conducting the public discussion and listening to the student’s defense, the dissertation was accepted. It was summarized as follows:
This study aims to decontaminate multi toxic pollutants, Reactive Blue (RB49), Reactive Green (RG19), Disperse Red (DR152), and Bisphenol-A (BPA), by immobilized enzymes in batch and continuous systems. Ten plant wastes were screened to extract the peroxidase enzyme and choose the one with the highest specific activity. The results have shown that cabbage legs are the best source for extracting peroxidase enzyme among other plant waste, with a specific activity of 1270 U/mg, by use phosphate buffer (0.1 M), 6.5 pH with (plant: buffer) extract ratio 1 :5 (W: V). The peroxidase enzyme was purified and characterization the enzyme activity and stability at different values of pH and temperature, At 6 pH and 40°C temperature. The effect of metal ions on the enzymes’ bioactivities was examined via the introduction of 5 mM of CuCl2, MgSO4, FeSO4, ZnCl2, AgNO3, HgCl2, and AlCl3 metal ions: enzyme in a 1:1 (v: v) ratio, the presence of FeSO4 and ZnCl2 ions increased the bioactivity of peroxidase, which led to 153% and 120% more activities, respectively. However, the presence of HgCl2, AgNO3, and CuCl2 ions resulted in a reduction of enzyme activity by 25, 53, and 60%, respectively. After that the removal efficiency of the crude and purified peroxidase enzyme before immobilized by covalent binding technique to remove pollutants after 1, 5, and 10 hours of incubation in the water bath at 40°C. After 10 hours, RB49, RG19, and DR 152 had decolorization percentages 86%, 78%, and 82% respectively as measured by using a crude enzyme. For the identical dyes, decolorization by pure enzyme was found to be 79%, 75%, and 80% respectively, which shows the high performance of the crude bioenzyme in degraded pollutants more than the purified enzyme. Inorganic low-cost support surfaces such as black stone (BS), sand (S), and quartz rock (QR), were utilized to immobilize the catalyst enzyme. One of the chemical process immobilization strategies used was the covalent binding technique. The resulting immobilized enzyme was analyzed by SEM, EDS, and BET analyses for morphological characteristics. The (QR) support showed an enzyme capacity of 12 mg protein / g support with 85% immobilization yield (IY%), which was the highest loaded than other supports. In a batch system, many operating parameters affecting the peroxidase enzyme’s activity in the pollutant degradation were investigated, Initial concentration was from (10-100) mg/l, a dose of the enzyme was (5-15) g, operation time (0.5-10) h at constant pH at 6 and constant temperature at 40 °C to design more efficiency biodegradation process. The best removal efficiency for RB49, RG19, DR152, BPA, and Mix pollutants was found to be 98%, 97, 92%, 82%, and 75% respectively. Analysis of Variance (ANOVA) results in the batch mode system showed that the quadratic model could be applied, with a highly significant model, (P-value) of < 0.0001 which is less than 0.05 for all pollutants. The determination coefficient R2 values for the removal percentage of models were determined to be 0.80, 0.88, 0.82, 0.85, and 0.83 for RB, RG, DR, BPA, and Mix pollutant respectively. These values indicate a powerful agreement between the predicted and experimental results, suggest a good fit for the model, and present high reliability. In a continuous system, different conditions were performed in the fixed bed reactor (PBR), initial concentration (10. 25, 50) mg/l, discharge (0.5, 1, 1.5) ml/min, and high enzymatic bed (5, 10, 15) cm. It was discovered that the best parameters were applied at values, of 10 mg/l concentration, 15cm bed height, and 0.5 ml/min discharge. The final stage of the trial involved evaluating how well worked Packed bed bioreactor performed on actual industry wastewater effluent from the wash sink of AL-HELLA textile factory.
The recommendations of this dissertation:
- Investigating of enzyme in another plant waste, seed hulls, fruit peels as a source of peroxidase.
- Studying the degradation of other pollutants such as industrial direct dyes, bisphenol-B, bisphenol-S, bisphenol-F, hydrocarbon compounds produced from the outputs of the textile, pharmaceutical, cosmetics, and plastic industries by the same enzyme.
- Conducting another chemical and biological test on samples after treatment with bioenzymes, such as BOD and TOC testing to determine the extent of the enzyme’s effect on removing toxicity.
- Adesign study for recycling treated water by using enzymes for the purpose of reusing it as a clean and treated water inside the factories.
