Upwelling
The major upwellings in the ocean are associated with the divergence of currents that bring deeper, colder, nutrient rich waters to the surface. There are at least five types of upwelling: coastal upwelling, large-scale wind-driven upwelling in the ocean interior, upwelling associated with eddies, topographically-associated upwelling, and broad-diffusive upwelling in the ocean interior.
Edinburgh Water Company
The works initially performed primary treatment only, to remove solids, and the remaining liquid was discharged into the sea through a pipeline. After the solids had been treated, they ware loaded onto a sludge disposal ship, the "Gardyloo", and dumped at sea. This practice ceased at the end of 1998, when dumping was banned by the EU Urban Waste Water Treatment Directive, and the plant was extended to perform secondary treatment on the sewage, after which it went to a landfill site. In 1999, the running of the plant was taken over from the East of Scotland Water Board by Stirling Water and Veolia, under a Private Finance Initiative. There are six sludge digesters on the site, which occupies , and they produce enough gas to generate 2.3 MW of electricity. It is expected that the site will become self-sufficient for energy within a few years. As part of the Seafield works, another interceptor sewer was constructed, some long and up to in diameter. Due to the wide variety of ground conditions, some of it was tunnelled, some constructed by cut-and-cover, and in places, the ground had to be frozen before excavation could proceed. In addition to the main treatment works at Seafield, there are smaller works at Newbridge, South Queensferry and Dalmeny.