The effect of primary treatment of wastewater in high rate algal pond systems: Biomass and bioenergy recovery

Abstract

The aim of this study was to assess the effect of primary treatment on the performance of two pilot-scale high rate algal ponds (HRAPs) treating urban wastewater, considering their treatment efficiency, biomass productivity, characteristics and biogas production potential. Results indicated that the primary treatment did not significantly affect the wastewater treatment efficiency (NH4 +-N removal of 93 and 91% and COD removal of 62 and 65% in HRAP with and without primary treatment, respectively). The HRAP without primary treatment had higher biodiversity and productivity (18 vs. 16 g VSS/m 2 d). Biomass from both systems presented good settling capacity. Results of biochemical methane potential test showed that co-digesting microalgae and primary sludge led to higher methane yields (238-258 mL CH4/g VS) compared with microalgae mono-digestion (189-225 mL CH4/g VS). Overall, HRAPs with and without primary treatment seem to be appropriate alternatives for combining wastewater treatment and bioenergy recovery.

Behavior of UV Filters, UV Blockers and Pharmaceuticals in High Rate Algal Ponds Treating Urban Wastewater

“…The average biomass productivity in the HRAP was 20.71 ± 6 g VSS m −2 day −1 (equivalent to 67.9 ± 17 mg VSS L −1 day −1 ), which is in accordance with results obtained in previous studies (ranging from 5 to 33 g VSS m −2 •day −1 [6,13]. Regarding the different microalgae species identified in the HRAP, Chlorella sp.…”

“…Oxygen is generated through photosynthesis and used by heterotrophic aerobic bacteria to degrade the organic matter present in the water. This way, these systems have the capacity of treating wastewater efficiently whereas producing microalgae biomass which, after an appropriate harvesting/separation technique from the aqueous phase, can be further profited to produce bioenergy (biogas) or other added-value bioproducts such as pigments, biofertilizers or bioplastics [5][6][7][8][9]. In consequence, if this biomass is managed properly, the waste generated during microalgae treatment (biomass) is considerably reduced, as well as the operation and maintenance costs when compared to conventional WWTPs.…”

“…Thus, the present study aims to evaluate the removal capacity of a HRAP at pilot scale, as secondary treatment, for 35 different PPCPs, including UV-filters and parabens (10), benzotriazoles (4), antibiotics (15) and other pharmaceuticals (6). The different removal pathways have been discussed for each pollutant, and the potential ecotoxicity of the HRAP effluent has been evaluated, estimating the risk quotients (HQs) associated to the PPCPs to ascertain a safe discharge in the receiving surface waters.…”

Beautification of Pokhara City with a Special Focus on Phewa Lake and Lakeside Area

“…A waterfall and air diffusers such as fountains can be used for water aeration. Furthermore, using algal treatment (aerobic treatment of waste), nitrogen, phosphorous, heavy metals, and several toxic compounds can be removed, and biomass and bioenergy can be recovered [23][24].…”

Microalgae: a sustainable adsorbent with high potential for upconcentration of indium(iii) from liquid process and waste streams

“…), with the presence of grazers (ciliate and flagellate protozoans). More details regarding the operational parameters and microbiological characteristics can be found in a previous study (Arashiro et al, 2019). Harvested biomass was thickened in laboratory Imhoff cones stored at 4°C for 24 hours.…”