In situ nutrient removal from aquaculture wastewater by aquatic vegetable Ipomoea aquatica on floating beds

Nutrient-rich effluents caused rising concern due to eutrophication of aquatic environment by utilization of a large amount of formula feed. Nutrient removal and water quality were investigated by planting aquatic vegetable on artificial beds in 36-m2 concrete fishponds. After treatment of 120 days, 30.6% of total nitrogen (TN) and 18.2% of total phosphorus (TP) were removed from the total input nutrients by 6-m2 aquatic vegetable Ipomoea aquatica. The concentrations of TN, TP, chemical oxygen demand (COD) and chlorophyll a in planted ponds were significantly lower than those in non-planted ponds (P<0.05). Transparency of water in planted ponds was much higher than that of control ponds. No significant differences in the concentration of total ammonia nitrogen (TAN), nitrate nitrogen (NO3−-N) and nitrite nitrogen (NO2−-N) were found between planted and non-planted ponds. These results suggested that planting aquatic vegetable with one-sixth covered area of the fishponds could efficiently remove nutrient and improve water quality.

Through the Proper Channels

This paper, based on a presidential address given to the British Section, Société des Ingénieurs Civils de France on 11 January 1974, examines the state of sea transport today and proposes a European Maritime Agreement along the lines of the Chicago convention for Civil Air Transport.The following definitions may be agreed.Channels all natural or artificial beds of rivers, estuaries or other bodies of water, or a body of water joining two seas, for example the Channel joining the North Sea with the Atlantic Ocean. The word also means ways of access or communications and methods of conveying nonmaterial things, such as in radio and radar systems.Proper means fit, suitable, efficient and safe; a secondary meaning is correct according to rule and accepted custom.