Urban Wastewater: Bioremediation with Chlorella vulgaris and Reuse as Irrigation Water

RENO, U; SCHMUCK, J; REGALDO, L; KERGARAVAT S.V; ROMERO, N; POLLA, W; GIMENEZ, L; GAGNETEN AM.

Montevideo

Congreso; SETAC Latin America 15th Biennial Meeting; 2023

Society of Environmental Toxicology and Chemistry

The treatment of urban wastewater (UWW) can vary depending on the geographical region and ontechnological and economic capabilities. In this sense, bioremediation emerges as an alternative to complex and expensive decontamination systems. A load of contaminants can be reduced by bioremediation processes obtaining a treated effluent that can be used for different applications. The objective of this work was to know the capacity of Chlorella vulgaris to bioremediate UWW of San Justo city (Santa Fe, Argentina) and to evaluate the reuse of treated UWW as irrigation water. UWW were collected from facultative lagoons and pretreated by filtration and centrifugation. From preliminary tests, it was found that C. vulgaris could grow at 100% UWW. In the definitive test, C. vulgaris was cultured in triplicated 1 L flasks containing 100 % UWW (inoculum 105 cells mL−1). Culture conditions were: continuous lighting (8000 lux), temperature (24±2°C), aeration and constant agitation. The chemical and biological oxygen demand (COD and BOD), nutrients (nitrates, nitrites, ammonium, total phosphorus) and fecal coliform bacteria were determined three times (day 1, day 4 (T1) and day 7 (T2)), to determine the microalgae removal efficiency (%). Next, thepotential of treated UWW as irrigation water was evaluated at T1 and T2 by a 120-h Lactuca sativa test. The concentrations tested at each time (T1, T2) were: 6.2, 12.5, 25, 50 and 100% of treated UWW and negative control (reconstituted water) for triplicate. The evaluated endpoints were: % germination (G), radicle length (RL) and hypocotyl length (HL) (mm). In T1, C. vulgaris showed removal of nutrients greater than 90%, reduction of BOD (73.20%), COD (39.70%), and bacteria (99.9%). In T2 an increase in BOD and COD was registered, which could be due to the release of organic compounds by the microalgae. The results showed that C. vulgaris reduced the parameters analyzed in UWW. In the L. sativa test, the highest %G was 88% at T2 (100% UWW treated). Significant differences (p