Keywords: MWWTPs, municipal wastewater treatment plants, Italy, abatement efficiency, Orbetello Lagoon, nutrients, PDP, phytodepuration pond, Central Tyrrhenian Sea, effluent monitoring, lagoon ecosystems, water quality, water pollution
Abatement efficiency of municipal wastewater treatment plants using different technologies (Orbetello Lagoon, Italy)
Two small-scale municipal wastewater treatment plants (Neghelli and Terrarossa) discharging effluents into a lagoon of great environmental interest and highly stressed by tourism (Orbetello, Italy) were monitored over the year 2001. We evaluated plants' performances developing a general efficiency indicator of removal to select the suitable purification technology (activated sludge, Neghelli vs. rotating biodisc reactor, Terrarossa). Unexpected, conventional technologies (activated sludge) had best performances (84% vs. 62%) with higher removal efficiencies for dissolved nutrients producing, on average, better final effluents. Even if Terrarossa showed a great improvement in summertime, during winter it seemed to be considerably affected by sea aerosol. Before the final discharge in lagoon, effluents were phytodepurated in a pond to reduce their nutrient load. Although data showed that the pond had further abatement efficiency over 80%, final outlet water represented a dangerous input for the lagoon ecosystem.