Operational decision support system for large combined sewage systems: Lisbon/Tagus estuary case study

Managing combined sewage systems in large cities discharging to coastal waters, often bearing recreational activities, remains a challenge. Studying the impacts of such discharges requires the development of specific models. Hydrodynamic and water quality modelling of coastal waters employs numerical methods and algorithms, leading to the design of complex models which require expert use. The use of such models as decision support tools to simulate discharge impacts and define adequate corrective measures could represent a key part in meeting this challenge. In this paper, the authors describe the work undertaken to develop an operational decision support system (ODSS) methodology aiming to enable wastewater utilities' non-expert staff to carry out user-friendly scenario analysis based on computational fluid dynamics simulations. This article depicts the application and validation of the ODSS to the combined sewage system and the Tagus estuary of the city of Lisbon in Portugal. The ODSS was used for simulating the effects in the receiving coastal waters of a discharge caused by a scheduled maintenance operation in the sewage infrastructure. Results show that the use of such ODSS by non-expert staff increases their decision capabilities and knowledge of the wastewater utility's contribution to reducing negative impacts of sewage discharges on the receiving water bodies.

Sudden cadmium increases in the digestive gland of scallop, Nodipecten nodosus L., farmed in the tropics

Cadmium bioaccumulation in Nodipecten nodosus reared on a marine farm in a tropical bay was measured in muscle tissue and the digestive glands in animals ranging from 6 to 16 months. No bioaccumulation tendencies regarding Cd concentration were observed in muscle tissue (below 1 μg g⁻¹), while in the digestive gland concentrations remained below 5 μg g⁻¹ until the organisms reached 10 months, and reached levels above 10 μg g⁻¹ from 12 months onwards (reaching 27 μg g⁻¹). This is the same bioaccumulation pattern noted in animals transplanted to a different Cd exposure. Allometry and environmental factors cannot explain this sudden increase.