The effect of carbon source on nitrate and ammonium removal from drinking water by immobilised Chlorella sorokiniana

Abstract

The feasibility of alginate-immobilised Chlorella sorokiniana for nitrate and ammonium removal from drinking water in regard to carbon source effects was studied in this paper. Three different natural carbon sources were tested in batch experiments with nitrate as nitrogen source: sucrose, grape juice and acacia honey. The nitrate removal efficiencies achieved at 50 mg/L of initial nitrate concentration under sucrose, grape juice and acacia honey were 93, 99 and 94 %, respectively. At 100 mg/L of nitrate, comparable efficiencies were obtained after approximately 3 days, whilst for acacia honey at 50 mg/L, it took only 2 days of cultivation and 3 days for the other two carbon sources. Grape juice and acacia honey showed better performances than sucrose, which must be linked to their chemical compositions. The study of the impact of biosorbent quantity on nitrate removal efficiency showed that sufficient nitrate removal efficiencies could be achieved with a beads/water ratio of 1:6.7 (v/v) or smaller. In addition, the beads' ages significantly impacted the nitrate removal. The removal of ammonium was studied in the presence of nitrate with acacia honey as carbon source.At the highest concentrations being tested (ammonium-30 mg/L and nitrate-50 mg/L), ammonium was completely removed in \3 days and nitrate by 81 % in 4 days, whereby the suitable beads/water ratio was 1:5. The priority of ammonium assimilation was noticed when compared to nitrate. According to the results, the alginateimmobilised C. sorokiniana represents a promising tool for the removal of nitrogen from drinking water sources.

Removal of heavy metal ions from drinking water by alginate-immobilised Chlorella sorokiniana

“…Immobilised algal beads were prepared using the procedure described in one of our previous studies, whereby algae-alginate gel suspension (2 % alginate) was dropped into 2 % CaCl 2 solution (Petrovič and Simonič 2015). Prepared beads with diameters in the range of 3.5 ± 0.5 mm (with cell numbers of around 4.5 9 10 5 -cells bead -1 ) were transferred to the algal growth medium and incubated under room conditions for 3-4 days.…”

“…functional groups of the alginate-immobilised algal beads unexposed to metals (Fig. 6, sample a), were examined precisely in our previous study (Petrovič and Simonič 2015), whereby the strongest absorption peak found at 3402 cm -1 corresponded to the -OH stretching of hydroxyls, indicating the presence of these groups on the biosorbent. The region 3600-3300 cm -1 showed, next to the O-H vibrations, the characteristic bands for N-H stretching vibrations, which can be attributed to algal biomass.…”

Cultivation of Chlorella sorokiniana using wastewaters from different processing units of the silk industry for enhancing biomass production and nutrient removal

“…The corresponding COD removal efficiencies by the end of cultivation were 89.3, 90.6, 91.1, 91.7, 92.9, and 92.7% in FC‐4×, FC‐8×, FR‐4×, FR‐8×, RC‐4×, and RC‐8×, respectively. It was reported that C. sorokiniana had the ability to grow in mixotrophic cultures, where both organic carbon and inorganic carbon could be assimilated concurrently by the algal cells for the synthesis of chemical compositions, such as protein, carbohydrates, chlorophylls, and lipids. Thus, when the mixed wastewaters were used as culture media, this alga would grow in the mixotrophic mode because organic carbon and inorganic carbon were supplied simultaneously.…”

Use of microalgae for treating municipal wastewater reverse osmosis concentrate and resource recovery

“…Although the biomass productivity of the immobilised algae was lower, the considerable adsorbability of the beads resulted in a higher overall nutrient removal efficiency compared with the suspended algae. The sorption capacity of the alginate for N (16.8 µg/g), P (2.7 µg/g), and OC (4.0 µg/g) showed that the presence of alginate algal beads in the ROC led to adsorption of nutrients by the bead matrix via pore-surface diffusion (Table A1), and hence nutrient removal additional to algal uptake (Wang et al, 1987;Petrovič and Simonič, 2015). Moreover, the negative surface charges on the alginate gel (Table A1) could result in electrostatic adsorption of positively charged organic molecules (Yi et al, 2018), and binding of calcium ions from the alginate beads with the phosphates could promote P removal (Luo et al, 2019).…”