Abstract
The need to reduce the costs associated with microalgae cultivation encouraged scientific research into coupling this process with wastewater treatment. Thus, the aim of this work was to assess the growth of Chlorella vulgaris (Chlorophyta) in different effluents from a municipal wastewater treatment plant (WWTP), namely secondary effluent (SE) and sludge run-off (SR). Assays were performed, under the same conditions, in triplicate with 4 dilution ratios of the wastewaters (25%, 50%, 75% and 100%) with the standard culture medium bold basal medium double nitrated (BBM2N) as a control. The capability of C. vulgaris for biomass production, chlorophyll synthesis and nutrients removal in the SE and SR was evaluated. The 25% SE and 25% SR showed increased specific growth rates (0.47 and 0.55 day−1, respectively) and higher biomass yields (8.64 × 107 and 1.95 × 107 cells/mL, respectively). Regarding the chlorophyll content, the 100% SR promoted the highest concentration of this pigment (2378 µg/L). This green microalga was also able to remove 94.8% of total phosphorus of SE, while in 50% SR, 31.2% was removed. Removal of 73.9% and 65.9% of total nitrogen in 50% and 100% SR, respectively, was also observed. C. vulgaris growth can, therefore, be maximized with the addition of municipal effluents, to optimize biomass production, while cleansing the effluents.
Highlights
Industrial e Empresarial da Figueira da Foz (Laboratório MAREFOZ), University of Coimbra, Rua das Department of Life Sciences, Faculty of Sciences and Technology, University of Coimbra, 3000-456 Coimbra, Portugal
C. vulgaris was able to grow in every tested concentration on both effluents (Figure 3), exhibiting a typical growth curve by presenting a lag and exponential phase
The higher cell density observed in the secondary effluent (SE) control was expected, because the growth medium used (BBM2N), is an optimized culture medium that is enriched in nutrients that are pivotal for C. vulgaris metabolic processes and growth [67]
Summary
Introduction with regard to jurisdictional claims in Aquatic and coastal ecosystems are essential, providing physico-chemical conditions that support diversified communities and several ecosystem services, such as shoreline stabilization, nutrient regulation, carbon sequestration, as well as the supply of food and energy resources [1,2,3] These ecosystems are often associated with highly populated areas, making these habitats even more susceptible, due to the increasing anthropogenic activity [4]. The discharge of urban and industrial effluents, as well as the intensification of agriculture or aquaculture, are some examples of the increasing anthropogenic stressors that endanger these habitats [5] The sum of these stressors often causes nitrogen and phosphorus enrichment of estuarine areas, leading to algal blooms–eutrophication—and the deterioration of water quality [4,5,6,7]
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