Abstract
In this study, we examined a Chlorella vulgaris-based system as a potential solution to change liquid waste, such as blackwater, into valuable products for agriculture while protecting waters from pollution without technical demanding pre-treatment. To evaluate the possibility of nutrient removal and biomass production from raw blackwater, four blackwater dilutions were tested at lab-scale: 50%, 30%, 20%, and 10%. The results showed that even the less diluted raw blackwater was a suitable growth medium for microalgae C. vulgaris. As expected, the optimum conditions were observed in 10% blackwater with the highest growth rate (0.265 d−1) and a nutrient removal efficiency of 99.6% for ammonium and 33.7% for phosphate. However, the highest biomass productivity (5.581 mg chlorophyll-a L−1 d−1) and total biomass (332.82 mg dry weight L−1) were achieved in 50% blackwater together with the highest chemical oxygen demand removal (81%) as a result of the highest nutrient content and thus prolonged growth phase. The results suggested that the dilution factor of 0.5 followed by microalgae cultivation with a hydraulic retention time of 14 days could offer the highest biomass production for the potential use in agriculture and, in parallel, a way to treat raw blackwater from source-separation sanitation systems.
Highlights
Municipal wastewater (WW) usually arrives as a mixture from toilets, kitchens, and bathrooms at a central WW treatment plant without closing material flows [1]
One part of the sample was used for the experiment, while the second part was used for the chemical analysis of pH, Total suspended solids (TSS), BOD5, chemical oxygen demand (COD), ammonium nitrogen (NH4 -N), total nitrogen (TN), total Kjeldahl nitrogen (TKN), total phosphorus (TP), nitrate-nitrogen (NO3 -N), and nitrite-nitrogen (NO2 -N) performed according to standard methods [23]
As a first step of the presented research, the properties of raw BW used for the experiment (Table 2) were analyzed and compared to literature data to evaluate the conditions for microalgae growth and biomass production as a base for system performance assessment
Summary
Municipal wastewater (WW) usually arrives as a mixture from toilets, kitchens, and bathrooms at a central WW treatment plant without closing material flows [1]. Nutrients in treated municipal water are, in most cases, lost and squandered through the discharge into water bodies, which can lead to eutrophication with detrimental effects to aquatic environments [2]. The two key nutrients in municipal WW are nitrogen (N) and phosphorous (P), which, if reused, could diminish eutrophication and potential pollution but their recovery could act as a sustainable fertilizer source [3]. The current challenge is to rethink the present WW treatment system and provide the technology to remove organic and inorganic compounds and recover them in a sustainable way
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