  In the present work we have conducted two studies. In the first study, we
investigated the role of plasma-activated water (PAW) in algae growth
inhibition and in the second study, efforts are made to understand the role of
PAW as a nitrogen source for algae growth enhancement. Two freshwater algae
species are selected for the present study named Chlorella Pyrenoidosa and
Chlorella Sorokiniana. The PAW is prepared using a pencil plasma jet and air as
a plasma forming gas. The plasma is characterized electrically and
identification of generated species in plasma is carried out using optical
emission spectroscopy. The study clearly indicated that more oxidizing PAW
exhibits algicidal effect. The PAW treatment with both the algae species
substantially decreased their growth compared to control. Moreover, the
morphology of algae cells showed damage and cells structure get ruptured after
PAW treatment. In the second study, a less reactive PAW (low oxidizing
potential) used as a nitrogen replacement in Bolds Basal Medium. The PAW-grown
Chlorella Pyrenoidosa and Chlorella Sorokiniana showed higher growth compared
to control. Also, a higher concentration of chlorophyll a and b, sugar, and
protein observed compared to control. Further, we observed lower antioxidant
enzymatic activities in PAW-grown algae compared to control. In conclusion, the
PAW has algicidal efficacy as well as can be used as nitrogen source in
aquaculture to enhance algae growth.
