Performance of a microalgal photobioreactor treating toilet wastewater: Pharmaceutically active compound removal and biomass harvesting

Abstract

In this study, a 1200L outdoor pilot scale microalgal photobioreactor (PBR) was used for toilet wastewater (WW) treatment and evaluate its ability to remove pharmaceutically active compounds (PhACs). The PBR was operated at two different hydraulic retention times (HRTs), which were 8 and 12days, during Period I (September-October) and Period II (October-December), respectively. Algal biomass concentrations varied by operating period because of seasonal changes. Nutrients (ammonia, nitrogen and total phosphorous) and chemical oxygen demand (COD) were monitored and efficiently removed in both periods (>80%), attaining the legislation limits. At the theoretical hydraulic steady state in both periods, pharmaceutical removal reached high levels (>48%). Two harvesting techniques were applied to the PBR microalgae effluent. Gravity sedimentation was efficient for biomass removal (>99% in 7min) in Period I when large particles, flocs and aggregates were present. In contrast, a longer sedimentation time was required when biomass was mainly composed of single cells (88% clarification in a 24h in Period II). The second harvesting technique investigated was the co-pelletization of algal biomass with the ligninolytic fungus Trametes versicolor, attaining >98% clarification for Period II biomass once pellets were formed. The novel technology of co-pelletization enabled the complete harvesting of single algae cells from the liquid medium in a sustainable way, which benefits the subsequent use of both biomass and the clarified effluent.

Utilization of Non-Living Microalgae Biomass from Two Different Strains for the Adsorptive Removal of Diclofenac from Water

“…Interest in microalgae-based wastewater treatment has increased in recent years since, while growing, these microorganisms are able to uptake pollutants like nutrients [6] and trace metals [7], but also emerging contaminants (ECs) such as pharmaceuticals [8][9][10]. The latter represent an especially worrying class of contaminants since they were designed to provoke a physiological response and their presence in the aquatic environment may affect non-target individuals.…”

“…The latter represent an especially worrying class of contaminants since they were designed to provoke a physiological response and their presence in the aquatic environment may affect non-target individuals. Among the different treatments proposed for the removal of pharmaceuticals from wastewater, microalgae-based systems have been proved to be effective either in close [8] or open [11] systems. Whatever the system configuration, biodegradation, together with bioadsorption and bioaccumulation, have been indicated as the main mechanisms for the removal of pharmaceuticals from wastewater [5].…”

The Use of Algae and Fungi for Removal of Pharmaceuticals by Bioremediation and Biosorption Processes: A Review

“…Hom-Diaz et al [177] observed that the removal of pharmaceuticals from domestic wastewater in a pilot-scale tubular photobioreactor, in two seasonal periods (September-October; October-December), was highly impacted by temperature and solar irradiation.…”

“…Some algae strains found in the literature [64,133,148,164,166,[168][169][170][176][177][178][179][180][182][183][184][185][186][187][188][189][190][191][192][193][194] proved to be effective in pharmaceutical removal (Table 1). Laboratory-scale batch assays [190] Biodegradation Laboratory-scale batch assays [191] Salicylic acid or paracetamol Pharmaceutical industry wastewater Algae…”

Review on Challenges and Limitations for Algae-Based Wastewater Treatment

“…A comprehensive review by [67] shows that similarly to constructed wetlands, EC removal rate in HRAPs varies from insignificant to complete reduction. Also, results from studies conducted in closed algae reactors [94] indicate that removal efficiency of emerging contaminants depends on chemical properties of each substance individually, and is largely determined by treatment system scale, operational regime and design as well as climatic conditions. Thus, it can be concluded that the unpredictable and selective performance makes algae production rather unsuitable for emerging contamination reduction, and likewise is the applicability of AAFW.…”