Bioremediation of cyanides in wastewater using bacterial and/or algal consortia / by Mona Fathy Abdel Mageed ; Supervisors Prof. Tamer Mohamed Essam , Marwa Tarek ElRakaiby.

Thesis (M.Sc.)-Cairo University, 2023.

Bibliography: pages 62-73.

A bacterial and algal strains were isolated from a wastewater sample collected from a wastewater treatment station in Egypt. The isolated bacterial strain was Gram-positive motile rods, identified as Bacillus licheniformis by 16S rRNA gene sequencing. It was later named Bacillus licheniformis MMT1. The strain was tested for its ability to biodegrade three selected cyanide-containing compounds: potassium cyanide (simple cyanide compound), potassium thiocyanate (sulfur-containing cyanide compound) and benzonitrile (aromatic cyanide compound). The biodegradation of sodium salicylate was also tested since it is commonly found as a co-pollutant with cyanides in wastewaters of pharmaceuticals, coke-ovens, and chemical industries. The bacterial isolate was able to remove up to 15.4 mM (1 g/l) of potassium cyanide, 29 mM (3 g/l) of benzonitrile and 6 mM (1 g/l) of sodium salicylate efficiently. As for potassium thiocyanate (KSCN), Bacillus licheniformis MMT1 failed to degrade it; however, KSCN had no inhibitory effect on the growth of either the bacterial or the algal strain.
The algal isolate was morphologically identified by electron microscopy as a strain of Chlorella spp. The toxicity of the pollutants was tested on the growth of the isolated algae; potassium cyanide (KCN) had the highest toxic effect on the algal growth, where 0.08 mM (0.05 g/l) of KCN inhibited 93 % of algal growth. While 14.6 mM (1.5 g/l) of benzonitrile hindered 96 % of algal growth and 75 % of the algal growth was suppressed by 51.4 mM (5 g/l) of KSCN. Finally, 31.2 mM (5 g /l) of sodium salicylate inhibited only 21 % of the algal growth.
Bacillus licheniformis MMT1 and the algal strain had neither inhibitory nor stimulatory effect on the growth of each other; therefore, they were utilized to construct a microcosm in a continuous stirred tank photobioreactor (CST-PBR) for the biodegradation of synthetic simulated wastewater containing the selected pollutants. Fertilization with 2 g/l of sodium bicarbonate added to the influent simulated wastewater was used as a source of CO2 to assist the algal growth in the surrounding toxic environment. A light cycle of 12h /12h was implemented to simulate natural conditions in the bio-treatment of the industrial wastewater.
The microcosm had the ability to detoxify an influent simulated wastewater containing up to 3.1 mM (0.2 g/l) of KCN, 0.97 mM (0.1 g/l) of benzonitrile and 3 mM (0.5 g/l) of sodium salicylate in 3.5 days hydraulic retention time (HRT). A biological assay was used to determine the detoxification efficiency of the photobioreactor (PBR). The post-treatment effluent was tested for its phytotoxic effect on the germination of seeds of Lepidium sativum. The removal of the pollutants was tested by HPLC and UV-spectrophotometric analyses. System failure was recorded when KCN concentration was increased to 3.8 mM (0.25 g/l). Attempts of recycling and increasing NaHCO3 concentration failed to restore the PBR biodegradation capacity.

نجحت هذه الدراسة في عزل سلالة بكتيرية قادرة على إزالة الملوثات السامة وسلالة من الطحالب شديدة التحمل للسيانيد من إحدى محطات معالجة الصرف المصرية. ومن المثير للاهتمام، أن العزلة البكتيرية Bacillus licheniformis MMT1 كانت تتمتع بأعلى قدرة تكسير مسجلة للسيانيدات في السنوات العشر الماضية على حد علمنا.

كانت السلالات البكتيرية والطحالب المعزولة متوافقة، وبالتالي تم استخدامها لبناء مفاعل بيولوجي للمعالجة المستمرة والتهوية عن طريق البناء الضوئي لمياه الصرف الصحي. كان المفاعل البيولوجي المؤسس قادرًا على معالجة وإزالة السموم بفعالية من مياه الصرف المحضرة المحملة بمزيج من مركبات السيانيد وساليسيلات الصوديوم بتركيزات تصل إلى 200 مجم / لتر KCN و 100 مجم / لتر بنزونيتريل و 100 مجم / لتر من ساليسيلات الصوديوم في HRT قصير نسبيًا من 3.5 أيام، وتم تعديل دورة الضوء / الظلام إلى 12/12 ساعة لمحاكاة ظروف النهار والليل الطبيعية.

الي حد علمنا، يمثل هذا العمل أول تجربة لعزل سلالة بكتيرية شديدة التكسير لمركبات السيانيد، واستخدام السلالة البكتيرية والطحالب المعزولة في انشاء مفاعل بيولوجي من ائتلاف الطحالب / البكتيريا لإزالة السموم من خليط الملوثات المختار تحت ظروف طبيعية تحاكي الواقع وامكانية تطبيق تلك المعالجة بشكل مستدام.

Issues also as CD.

Text in English and abstract in Arabic & English.