Banca de DEFESA: JAQUELINE DOS SANTOS

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : JAQUELINE DOS SANTOS
DATE: 31/10/2022
TIME: 14:00
LOCAL: https://meet.google.com/xhr-rmgo-kwr
TITLE:

Study of semicontinuous process of whey treatment by microalgae in open system

KEY WORDS:

Biological treatment, Tetradesmus obliquus, dairy industry

PAGES: 82
BIG AREA: Engenharias
AREA: Engenharia Química
SUBÁREA: Processos Industriais de Engenharia Química
SPECIALTY: Processos Bioquímicos
SUMMARY:

The dairy industry is one of the most important sectors of the food industry, generating a large amount of effluents, mainly whey. This effluent is marked by the high concentration of COD (chemical oxygen demand), TN (total nitrogen) and FT (total phosphate), which can, for example, generate eutrophication in water bodies when discarded without proper treatment. Microalgae are photosynthetic microorganisms that have high efficiency in removing nitrogen and phosphate, and can be cultivated in open systems, even though this type of process is subject to contamination, they have the advantage of operating at lower costs and being able to associate natural microorganisms in symbiotic systems with microalgae for the wastewater treatment. In this sense, this work aims to evaluate the use of the microalgae Tetradesmus obliquus LCE-01 in the treatment of diluted whey as well as to evaluate the semi-continuous process in an open system without forced aeration. For this, the remediation process was studied using the whey concentration of 1 and 4 % under conditions of magnetic stirring and constant illumination (100 µmol m^-2 s^-1). The experiment was carried out in batch mode for the first 7 days and later in semi-continuous mode with volumetric replacement rates (TRV) of 20, 40, 60 and 80% in a feedback time (or volumetric replacement) of 3 days (setting retention times hydraulic – HRT of 15, 7.5, 5 and 3.75 days, respectively) and with a total process time of 16 days (1 batch of 7 days and 3 semi-continuous cycles of 3 days), keeping the pH between 8 - 8.5. The experiments were monitored for pH, cell dry weight, COD, NT and FT. Regarding COD, residual values of 200-250 and 240-600 mg L^-1, for 1 and 4% of whey, are still high according to the European standard for discharging of 125 mg L^-1. Regarding NT, residual values were 6-9.8 and 25-33 mg L^-1 with maximum removal rates of 80 and 60% for 1 and 4%, respectively, with some experiments respecting the release limit of 10- 15 mg L^-1 and 70-80% minimum removal rate. For FT, the residues were 1-6 and 9-16 mg L^-1, also in some experiments fitting the European norm for release of 3.1-6.2 mg L^-1, despite having had a maximum efficiency removal rate of 70 and 30% for 1 and 4% of whey, respectively. It was noticed that the semi-continuous process showed stability of operation and that it needs improvements to remove a greater amount of contaminant. It was produced between 250-600 mg L^-1 of cell dry weight, with the highest values obtained for the 4% of whey (higher organic load). It was also verified the importance of daily maintenance of the pH of the system to values between 8-8.5 in order to effectively conserve the microalgae within the system, since at acidic pHs, they tend to die. TRVs of up to 40% for all contaminants had higher removal rates (except 60 and 80% for 1% of whey but it needs to be re-evaluated). As suggestions for improving the system, we can mention the inclusion of forced aeration, longer refeeding times and insertion of filamentous bacteria or fungi (microbial symbiosis with microalgae). It was noticed that the organic load imposed with the 4% of diluted whey was in excess, mainly for NT and FT and sequential steps may be necessary to stabilize the residual parameters of these contaminants.

BANKING MEMBERS:
Presidente - 3081569 - CARLOS EDUARDO DE FARIAS SILVA
Interna - 1456420 - RENATA MARIA ROSAS GARCIA ALMEIDA
Externa ao Programa - 1296115 - ALBANISE ENIDE DA SILVA