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

Abstract

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.

Continuous 3-year outdoor operation of a flat-panel membrane photobioreactor to treat effluent from an anaerobic membrane bioreactor

“…To avoid serious pollution problems, wastewater effluents must be properly treated prior to their discharge into natural water bodies (Song et al, 2018). Although urban wastewater treatment plants (WWTPs) are now extremely efficient as regards removing pollutants, they consume huge amounts of energy (Ling et al, 2019;Marazzi et al, 2019) and the nutrients are usually lost by nitrogen stripping or phosphorus precipitation (Whitton et al, 2016).…”

“…Apart from ambient conditions (mainly solar light and temperature), there are many other factors that influence microalgae growth: PBR design, mixing rate, nutrient loading rates, microalgae strains, biomass and hydraulic retention time (BRT, HRT), competition with other microorganisms, inhibition by toxic substances, etc. (Cho et al, 2019;Marazzi et al, 2019). Some of these factors have been independently evaluated in outdoor flat-panel MPBRs in previous studies ( Table 1).…”

Sustainable Sewage Sludge Management: From Current Practices to Emerging Nutrient Recovery Technologies

“…Reject liquid from sludge treatment (sidestream) in a typical municipal WWTP has 7 to 12 times higher N and P concertation as compared to the mainstream and therefore, is the first target for NR due to smaller volume and Sustainability 2019, 11, 3435 3 of 12 better recovery rates. However, different N and P concentrations have been stated in other studies, too [10,11].…”

“…More than 15 full-scale units mainly producing struvite Pearl, Multiform, Airprex see [10] Lack of economic drivers and regulations for nutrient recovery [10] Europe Germany (10), Netherlands (10), Belgium (6), France (2), Spain (2), Italy (1), UK (2), Denmark (4) Variety of technologies including Airprex, Anphos, Elophos see [10] Mainly producing struvite from both municipal and industrial wastewater It can be concluded that the low market price for fertilizers from phosphate rocks challenge the economic viability of nutrient recovery technologies, especially when the candidate technology does not provide additional operational benefits or a directly marketable product. The integration potential of a technology or a recovered material into existing infrastructure increases the chance to be in the successful class technologies.…”

Interactions between Microalgae and Bacteria in the Treatment of Wastewater from Milk Whey Processing

“…Microalgae/bacteria consortia have been recently suggested as effective in the treatment of different kinds of urban [15][16][17][18], as well as agro-industrial [19], wastewater. According to some authors, microalgae-based processes are not suitable to treat dairy wastewater as such, due to the high polluting load they carry [20,21].…”