Activity assessment of microalgal-bacterial consortia based on respirometric tests

Rossi, S.; Bellucci, Micol; Marazzi, Francesca; Mezzanotte, Valeria; Ficara, Elena

doi:10.2166/wst.2018.078

Cited by 37 publications

(29 citation statements)

References 21 publications

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“…Microscopic observation revealed that the inoculum was made of a mixed microalgae/bacteria community including mainly Scenedesmus spp. and Chlorella spp., in agreement with previous studies [24][25][26][27].…”

Section: Pilot Plant and Experimental Designsupporting

confidence: 94%

Outdoor pilot trial integrating a sidestream microalgae process for the treatment of centrate under non optimal climate conditions

et al. 2019

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This study was carried out to assess the efficiency of a pilot-scale bubble-column reactor to remove nitrogen in centrate from the biosolid dewatering of a municipal wastewater treatment plant whilst producing biomass for agricultural purposes. The column was inoculated with a mixed community of Scenedesmus and Chlorella spp. and operated outdoor in batch for 55 days and in continuous for further 130 days. In continuous, the average daily biomass productivity was 40 ± 62 mg TSS L −1 d −1 and the average NH 4 +-N removal was 20 ± 10 mg L −1 d −1. Nitrification was fostered by photo-oxygenation leading to the oxidation of 34 ± 27% of the incoming ammonia nitrogen. Microalgal and bacterial activity inside the column was analyzed by the Generalized Linear Models in order to understand the main factors affecting the process performances. Microalgal growth was affected positively by the NH 4 +-N content in the influent and negatively by the amount of TSS entering the system, probably due to the competition between microalgae and bacteria for phosphorus and other nutrients. The removal rate of NH 4 +-N was positively affected by NH 4 +-N in (influent concentration) and by pH, whose increase fosters stripping, and decreased for increasing NH 3-N concentrations, responsible for inhibiting nitrifying bacteria. NH 4 +-N oxidation was the result of complex interactions between algae and bacteria and was also affected by flow and solar radiation. No other specific limiting factors have been highlighted. The possibility of improving the process performance by controlling pH, by supplying off-gas as CO 2 additional source, appears as an interesting option. In view of a scale-up, the most relevant expected result would be the energy saving due to the decrease in the oxygen demand for nitrification in the water line. The microalgal biomass grown on centrate was suitable for agricultural use due to its low contamination by heavy metals.

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Section: Pilot Plant and Experimental Designsupporting

confidence: 94%

Outdoor pilot trial integrating a sidestream microalgae process for the treatment of centrate under non optimal climate conditions

et al. 2019

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“…For this procedure, 0.8 mL of ammonium chloride (3 g/L) was added as the ammonium source. Among the different ammonium sources that have been used to evaluate nitrifying activity in activated sludge processes and microalgae-bacteria consortia, ammonium chloride has been the most extensively utilized [17,18]. The sample was exposed to four light-dark cycles of 4 min each.…”

Section: Photosynthesis and Respiration Rate Measurementsmentioning

confidence: 99%

“…However, respirometry methods have been generally applied to pure microalgae cultures, while in wastewater processes is indispensable to consider the existence of microalgae-bacteria consortia. On this issue, some authors have started to develop respirometry methods for studying microalgae-bacteria consortia by evaluating both microalgae and bacterial activity, specifically nitrifying activity in microalgae wastewater treatment [17].…”

Section: Introductionmentioning

confidence: 99%

A novel photo-respirometry method to characterize consortia in microalgae-related wastewater treatment processes

et al. 2020

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In this paper, a new photo-respirometry method for determining the rates of the main metabolic processes of microalgae-bacteria consortia in microalgae-based wastewater treatment processes has been developed and tested. The proposed protocol consists on applying dark and light periods to a microalgae-bacteria consortium in the presence of different substrates and measuring the rate of oxygen production. This allows determining the activity of microalgae, heterotrophic bacteria and nitrifying bacteria separately. The method has been optimized in terms of the operation strategy, including the starvation period required, the biomass concentration and the irradiance during the measurements. Results show that a starvation period of one to three days is necessary depending on the nutrient concentration. The optimal experimental conditions determined were a biomass concentration of 0.5 g/L and an irradiance of 200 μmol photons/m 2 •s. Furthermore, microalgae-bacteria samples from seven photobioreactors (indoor and outdoor) with different nutrient sources have been evaluated applying the methodology proposed. Regardless of the wastewater type, the microalgae activity is the main metabolic process, with heterotrophic activity increasing along with the chemical oxygen demand (COD) in the wastewater. Nitrifying activity was only observed when high ammonium concentrations were present. The developed method is a powerful tool to adequately manage and operate wastewater treatment processes using microalgae/bacteria consortia, providing valuable information to model wastewater treatment systems with microalgae and determine kinetic parameters.

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“…A first approach on the evaluation of nitrite inhibition (at lab-scale) was carried out by respirometries, which allowed obtaining the OPR of microalgae. OPR was selected as an indicator of microalgae performance as it has been widely reported to be proportional to microalgae photosynthetic activity (Rossi et al, 2018).…”

Section: Short-term Exposure To Nitritementioning

confidence: 99%

“…It must be noted that the OPR obtained by Eq. 1 corresponds to a net value which is the result of several processes: i) microalgae photosynthesis; ii) activity of nitrifying bacteria; iii) respiration of heterotrophic bacteria; and iv) microalgae photorespiration (Rossi et al, 2018).…”

Section: Short-term Exposure To Nitritementioning

confidence: 99%

Nitrite inhibition of microalgae induced by the competition between microalgae and nitrifying bacteria

et al. 2020

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Outdoor microalgae cultivation systems treating anaerobic membrane bioreactor (AnMBR) effluents usually present ammonium oxidising bacteria (AOB) competition with microalgae for ammonium uptake, which can cause nitrite accumulation. In literature, nitrite effects over microalgae have shown controversial results. The present study evaluates the nitrite inhibition role in a microalgae-nitrifying bacteria culture. For this purpose, pilot-and lab-scale assays were carried out. During the continuous outdoor operation of the membrane photobioreactor (MPBR) plant, biomass retention time (BRT) of 2 d favoured AOB activity, which caused nitrite accumulation. This nitrite was confirmed to inhibit microalgae performance. Specifically, continuous 5-d lab-scale assays showed a reduction in the nitrogen recovery efficiency by 32, 42 and 80% when nitrite concentration in the culture accounted for 5, 10 and 20 mg N•L-1 , respectively. On the contrary, short 30-min exposure to nitrite showed no significant differences in 2 the photosynthetic activity of microalgae under nitrite concentrations of 0, 5, 10 and 20 mg N•L-1. On the other hand, when the MPBR plant was operated at 2.5-d BRT, the nitrite concentration was reduced to negligible values due to increasing activity of microalgae and nitrite oxidising bacteria (NOB). This allowed obtaining maximum MPBR performance; i.e. nitrogen recovery rate (NRR) and biomass productivity of 19.7 ± 3.3 mg N•L-1 •d-1 and 139 ± 35 mg VSS•L-1 •d-1 , respectively; while nitrification rate (NOxR) reached the lowest value (13.5 ± 3.4 mg N•L-1 •d-1). Long BRT of 4.5 d favoured NOB growth, avoiding nitrite inhibition. However, it implied a decrease in microalgae growth and the accumulation of nitrate in the MPBR effluent. Hence, it seems that optimum BRT has to be within the range 2-4.5 d in order to favour microalgae growth with respect to AOB and NOB.

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Activity assessment of microalgal-bacterial consortia based on respirometric tests

Cited by 37 publications

References 21 publications

Outdoor pilot trial integrating a sidestream microalgae process for the treatment of centrate under non optimal climate conditions

Outdoor pilot trial integrating a sidestream microalgae process for the treatment of centrate under non optimal climate conditions

A novel photo-respirometry method to characterize consortia in microalgae-related wastewater treatment processes

Nitrite inhibition of microalgae induced by the competition between microalgae and nitrifying bacteria

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