Elimination of environmental impact loads from processed efflux

Abstract

The degradation of seawater quality in enclosed coastal sea area such as organic pollution and eutrophication is mainly caused by processed efflux from sewerage facilities. It has not been well understood that the processed efflux still dissolves high concentrations of nitrogen compounds and phosphates. Disposal capacity and supply of electric energy in sewerage facilities are necessary to be improved to remove such kind of environmental impact loads from sewage and drainage. To solve the problem without using big facilities and big amount of electricity, we have to study and consider the possibility of the natural purifying capacity of marine ecosystem in the coastal sea area. The red tides are phenomena of excess amount of phytoplankton growth in the eutrophic seawater. It means that some kinds of algae or phytoplankton can be used for purifying sewage and drainage which contains nitrogen compounds and phosphates, namely for assimilating nutrient loads. The authors proposed the "Eco-Platform" in the previous paper, and one of the key functions of the Eco-Platform is algae proliferation system. In the present paper, they show that the sea lettuce (Ulvales) gives a good solution to the problem. It grows very rapidly with assimilating nutrient loads in seawater under optimally controlled light and water temperature conditions. They also show that the energy-recycle in a broad sense can be achieved by processing the proliferated sea lettuce in the subcritical-hot-water decomposition system and subsequent methane fermentation system.