Abstract
ABSTRACT Phytoremediation, as the implementation of microalgae in the treatment of effluents, is used to remove nitrogen compounds and phosphorus that can cause eutrophication in receiving water bodies. The present study evaluated the phytoremediation of urban and fish farming wastewater and growth performance of Litopenaeus vannamei using microalgae Chlorella vulgaris. Microalgae were cultivated stationary with three treatments: T1 sewage treatment station effluent (STS), T2 fish farming effluent (FF) and T3 with standard medium (SM) Guillard f/2), conducted in quintuplicate for each culture medium, using a 20 L carboy for eight days. 5.0 L inoculum (25%) plus 15 L culture medium, T1 STS, T2 FF and T3 SM (75% of each) were used to start the experiment. The shrimp experiment was realized with three treatments in quintuplicates, completely randomized design, during 15 days. The animals were maintained in tanks of 100 L under constantly aerated, resulting in a concentration above 5.0 mg L− 1 of dissolved oxygen, in a density of 70 animals m-3, fed four times per day (8:00, 11:00, 14:00 and 16:00 h) offering to T1 commercial feed (C-Feed) with 35% crude protein, T2 and T3 with commercial feed plus addition of 5.0% dry biomass of C. vulgaris. The best result for algal perfomance, lipid biomass and nutrient removal was with Fish farm wastewater. The additive with the highest performance was FF-Feed. C. vulgaris has a high potential for removing nutrients from wastewater, producing biomass and lipids, in addition to increasing shrimp productivity.
Highlights
The generation of urban and aquaculture effluents, rich mainly in nitrogen and phosphorus, are challenges faced by society, a large part of aquaculture projects and cities in Brazil do not have an adequate disposal of their effluents before discarding them, which can contaminate and eutrophicate receiving water bodies with excessive growth of macrophytes, cyanophyceae, low specimen diversity, anaerobic conditions and mortality of aquatic organisms (Evans et al, 2017)
The microalgae C. vulgaris strain was obtained from the algal culture collection of the Aquaculture Technology Laboratory of the Federal Institute of Ceará (LTA - IFCE) - Aracati Campus, where it is kept in a Guillard f/2 medium (Guillard, 1975) under controlled temperature conditions (20.0±1.0 oC) and light intensity maintained at 54 μmol m-2 s-1 using a fluorescent light with a controlled photoperiod (16 h dark:08 h light)
The effluents used as a culture medium, urban sewage and fish farming were collected in sewage treatment station (STS) and fish farming (FF) of IFCE - Aracati Campus, respectively
Summary
The generation of urban and aquaculture effluents, rich mainly in nitrogen and phosphorus, are challenges faced by society, a large part of aquaculture projects and cities in Brazil do not have an adequate disposal of their effluents before discarding them, which can contaminate and eutrophicate receiving water bodies with excessive growth of macrophytes, cyanophyceae, low specimen diversity, anaerobic conditions and mortality of aquatic organisms (Evans et al, 2017). Most studies on effluent treatment are based on physical processes such as stabilization ponds and decanters, chemicals with use flocculation or flotation compounds and biological processes such as water recirculation system that use aggregated biofilters with decantation tanks and processes with and without the presence of oxygen (Arun et al, 2017) These processes are mainly aimed at removing nitrogenous compounds and phosphorus, resulting in steps with disadvantages due to high infrastructure and professional costs, high operational complexity, demanding large areas, in addition to producing large amounts of sludge (Ajayan; Harilal; Selvaraju, 2018). Some bioremoval studies work with plants, such as wetlands that use superior plants and macroalgae (Sujuan et al, 2021; Saberi et al, 2020), both processes achieve a lower removal of nitrogen compounds and phosphorus when compared to the use of microalgae, in addition to requiring a longer period for the development of plants and macroalgae These characteristics make these processes more environmentally and financially costly (Yajing et al, 2021). Several studies demonstrate the advances in the efficiency of microalgae in the treatment of urban (Pacheco et al, 2021), industrial (Rajak; Jacob; Kim, 2020) and agricultural effluents (Wen et al, 2017), indicating the possible applications of the algal biomass produced, but without using it
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