UNDIP, Semarang (March 5) – The Postgraduate School of Universitas Diponegoro (UNDIP) continues to produce high-quality doctoral graduates through a dissertation defense held on Monday, February 24, 2025. Purwono, a student from the Doctoral Program in Environmental Science, successfully graduated with the highest distinction (Cum Laude), achieving a perfect GPA of 4.00. He completed his studies in just 2 years and 6 months, becoming the 131st Doctoral graduate in Environmental Science.
The dissertation defense, held in the Main Courtroom, 1st Floor, TTB-A Building, Postgraduate School of UNDIP, was attended by the examination committee: Prof. Ir. Mochamad Agung Wibowo, M.M., M.Sc., Ph.D. (Chairman/Examiner); Dr. Budi Warsito, S.Si., M.Si. (Secretary/Examiner); Prof. Ir. Didi Dwi Anggoro, M.Eng., Ph.D., IPU, ASEAN Eng. (Examiner 1); Dr. Ing. Sudarno, S.T., M.Sc. (Examiner 2); Prof. Dr.Eng. Ir. Arief Budiman, M.S., IPU. (External Examiner); Prof. Dr. Ir. Hadiyanto, S.T., M.Sc., IPU (Promoter); and Prof. Ir. Mochamad Arief Budihardjo, S.T., M.Eng.Sc, Env.Eng, Ph.D., IPM., ASEAN Eng. (Co-Promoter).
On this occasion, Purwono presented his dissertation titled “Innovation of Spiral Electrocoagulation to Optimize Microalgae Harvesting and HHO Gas Production.” His research highlights the crucial role of microalgae in addressing issues related to waste management, energy crises, and food shortages. However, challenges persist in the development of reliable and cost-effective microalgae harvesting and mass production techniques due to small cell size, low biomass concentration, and electrostatic repulsion between cells.
The study aims to analyze the microalgae harvesting process using Spiral Electrocoagulation (SEC), HHO gas production, wastewater quality, and Generation Z consumers’ knowledge, awareness, acceptance, and willingness to pay for microalgae-based fuels.
Using a combination of Scopus-based bibliometric analysis, laboratory experiments, and surveys, Purwono achieved significant breakthroughs. He harvested Chlorella sp. with 97.34% efficiency using SEC at 15V for 20 minutes. Dunaliella salina harvesting in under 5 minutes resulted in a maximum dissolved hydrogen gas concentration of 820 ppb at 18V for 3 minutes. Scaling up the reactor to 1500 mL produced a dissolved hydrogen gas concentration of 1753 ppb and a total HHO gas volume of 1978 mL after 30 minutes.
In his research, Purwono successfully reduced the ammonia nitrogen (TAN) concentration in wastewater by 98.8% using electrocoagulation within 5 minutes. D. salina harvesting efficiency reached 93.72%, with nitrate and phosphate concentration in wastewater reduced by 97% in just one minute at 20V. Response Surface Methodology (RSM) analysis determined optimal harvesting conditions for D. salina at 25V, 4.17 minutes, and a reactor angle of 68.39 degrees, achieving 85.77% efficiency.
Survey results revealed strong public support for the development of microalgae as a biofuel source, with respondents understanding the benefits of microalgae, being willing to pay more for eco-friendly fuels, and prioritizing environmental factors in purchasing decisions. These findings open new opportunities for utilizing microalgae to address global challenges.
Expressing his gratitude, Purwono stated, “Alhamdulillah, I am deeply grateful. The support from my family and the academic community at UNDIP has been instrumental in my success. The facilities, infrastructure, and mental encouragement provided by the Postgraduate School were invaluable.”
He further shared that the entire process, from preparation to defense, went smoothly, thanks to his hard work and unwavering support from both his family and UNDIP’s academic environment.
Purwono’s achievement stands as a testament to the Postgraduate School of UNDIP’s commitment to producing academically excellent doctoral graduates who can make meaningful contributions to society, science, and technology.
