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Abstract Wastewater from tofu industry contains suspended and organic matter which, if discharged directly into the waters, can degrade water quality. One method of wastewater treatment that can be done is phycoremediation, which utilizes the activity of microalgae which can assimilate N and P in tofu wastewater as a source of nutrients for growth. The addition of salicylic acid as elicitor can increase microalgal biomass, although administration of salicylic acid at high concentrations potentially could inhibit microalgae growth. Therefore, it is necessary to know the right concentration of salicylic acid which could increase microalgae biomass. In this study, cultivation of mixed microalgae Chlorella vulgaris , and Nannochloropsis oculata , with a ratio of 1:1 (v/v) was carried out for 7 days at the Open Raceway Pond (ORP) with a working volume of 55 L. The growth medium used was tofu wastewater with a concentration of 16% (v/v) of the working volume. On the fifth day, variations were made with the addition of salicylic acid 0 μM (control), 20 μM, and 200 μM. The use of mixed cultures was expected to increase resistance to various abiotic and biotic conditions, as well as optimize resource utilization. Parameters measured included specific growth rate, pH, initial and final levels of nitrate, orthophosphate, BOD, and COD. Mixed culture of C. vulgaris and N. oculata with the addition of 20 μM salicylic acid produced the best growth, with a specific growth rate of 0.66/day. The addition of 20 μM salicylic acid also resulted in the highest reduction in wastewater parameters, with the percentage of reductions in nitrate concentration (57.67%), orthophosphate (44.09%), BOD (62.48%), and COD (56.09%). The result showed that phycoremediation of tofu wastewater can be best carried out by utilizing a mixed culture of C. vulgaris and N. oculata with the addition of 20 μM salicylic acid.
Taufikurahman et al. (Sun,) studied this question.