Evaluation of primary treatment and loading regimes in the removal of pharmaceuticals and personal care products from urban wastewaters by subsurface-flow constructed wetlands

Abstract

The ability of several mesocosm-scale horizontal subsurface flow (SSF) constructed wetlands (CW) to remove pharmaceuticals and personal care products (PPCPs) from urban wastewater was assessed in the winter and summer of 2008. As CWs are generally used as secondary or tertiary wastewater treatment systems, their efficacy was compared when fed from two different primary treatment systems, a sedimentation tank and an anaerobic hydrolysis upflow sludge bed reactor (HUSB). The influence of plants (Phragmites australis) in the CWs and their feeding regime (continuous flow or batch flow) on PPCP removal were also monitored. One of the CWs was replicated and operated simultaneously in Barcelona and León, Spain, in order to study the effect of environmental conditions on PPCP removal. All systems operated in the open air. The sedimentation tank offered slightly better removal values throughout the experimental period than the HUSB. The presence of P. australis enhanced the removal of salicylic acid, galaxolide, tonalide and methyl dihydrojasmonate, but only in summer (when plants were more active). The use of a batch flow or a continuous flow made very little difference to PPCP removal efficiency. When the two mesocosm replicates were compared, temperature proved to be one of the most determining parameters affecting PPCP elimination, with naproxen, ibuprofen, diclofenac, caffeine, galaxolide, tonalide and methyl dihydrojasmonate being removed in SSF-CWs more efficiently at higher temperatures. In general, the most easily removed PPCPs in planted CWs were caffeine (14 ± 74%–84 ± 7% in winter, 98 ± 1%–99 ± 1% in summer), methyl dihydrojasmonate (28 ± 21%–63 ± 17% in winter, 93 ± 2%–98 ± 1% in summer) and salicylic acid (0%–97 ± 4% in winter, 41 ± 40%–89 ± 9% in summer), followed by naproxen (0%–41 ± 16% in winter, 60 ± 18%–95 ± 4% in summer) and ibuprofen (0%–47 ± 26% in winter, 35 ± 12%–99 ± 1% in summer). Other substances experimented lower removal efficiencies, like ketoprofen (4 ± 27%–27 ± 14% in winter, 0%–37 ± 32% in summer), diclofenac (0%–22 ± 22% in winter, 0%–71 ± 8% in summer), carbamazepine (0%–9 ± 100% in winter, 0%–58 ± 21% in summer), galaxolide (0% in winter, 25 ± 14%–87 ± 5% in summer) and tonalide (0% in winter, 32 ± 12%–76 ± 12% in summer).