Abstract
The present study evaluated the efficiency of a high rate algal pond (HRAP) at pilot scale to remove pharmaceuticals and personal care products (PPCPs) from urban wastewater, including UV-filters and parabens (10), benzotriazoles (4), antibiotics (15), anti-inflammatories (3) and other pharmaceuticals (3). A total of 35 compounds were targeted, of which 21 were detected in the influent wastewater to the HRAP. Removals (RE%) for pharmaceuticals were variable, with efficient eliminations for atenolol (84%) and sulfathiazole (100%), whereas the anti-inflammatories naproxen and ketoprofen were only partially removed <50%. Benzotriazoles showed elimination rates similar to those of conventional WWTPs, with RE% ranging from no elimination to 51% for the UV filter benzophenone-3 (BP3) and 100% for 4-methylbenzilidenecamphor (4MBC). Hazard quotients (HQs) were estimated for those compounds not fully eliminated in the HRAP, as well as the cumulative ecotoxicity in the resulting effluent. The majority of the compounds yielded HQs < 0.1, meaning that no environmental risk would be derived from their discharge. Overall, these results clearly indicate that HRAPs are a reliable, green and cost-effective alternative to intensive wastewater treatment, yielding promising results removing these contaminants.
Highlights
Nature-based, low-cost treatment systems are gradually becoming feasible alternatives to conventional secondary/biological treatment in wastewater treatment plants (WWTP), especially to cover the needs of small populations with no access to sanitary facilities
The total suspended solids (TSS) removal efficiency of the high rate algal pond (HRAP) was 77.8%, which is higher than other results obtained previously (52.6%) in bigger HRAPs [34]
The chemical oxygen demand (COD) removal observed in the HRAP (60%) was in accordance with the results obtained in the same system operated and monitored for one year [10] and with those observed in different HRAPs [35,36]
Summary
Nature-based, low-cost treatment systems are gradually becoming feasible alternatives to conventional secondary/biological treatment (activated sludge) in wastewater treatment plants (WWTP), especially to cover the needs of small populations (up to 10,000 inhabitants) with no access to sanitary facilities. Microalgae-based systems, and high rate algal ponds (HRAP), have already been used for decades for wastewater treatment [1,2]. They were introduced to improve the efficiency of stabilization ponds, being generally shallower to ensure light penetration, having a higher rate of oxygen production and operating under shorter retention times. Compared to conventional WWTPs, HRAPs do not require external aeration due to microalgae photosynthesis nor any chemical inputs during the treatment process [3,4].
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