Application of solidified sea bottom sediments into environmental bioremediation materials

Since dredged sea bottom sediments normally give off a horrible smell, the limitation of disposal places has become a serious problem in Japan. Hence, development of an alternative system to readily treat dredged sea bottom sediments is therefore needed. The development of “value-added” reused products from these sediments offers particular benefits both in terms of resource recovery and protection of the environment. We developed an in situ solidification system for the treatment of sea bottom sediments, the “Hi-Biah-System (HBS)”. Firstly, this review deals with solidified sea bottom sediments for the construction of an artificial tidal flat in Ago Bay, Japan. The environmental conditions (pH, oxidation–reduction potential (ORP), acid volatile sulphide (AVS), loss on ignition (LOI), water content (WC), chemical oxygen demand (COD), total organic carbon (TOC), total nitrogen (T-N), chlorophyll a and particle size) were then monitored in the constructed tidal flat. The number of benthos individuals and growth of short-necked clams (Ruditapes philippinarum) in the artificial tidal flat were also evaluated. The environmental conditions, number of benthos individuals and growth of short-necked clams in the artificial tidal flat were shown to be similar to those observed in a natural tidal flat. Next, the potential use of solidified sea bottom sediments as soil parent material in the germination/growth of seagrass is presented. The soil parent material consisting of solidified sediments obtained using HBS plus soil conditioner and hardener seems to be effective for the germination of Zostera marina. The best growth after six months was observed in plants grown in soil parent material consisting of a mixture of solidified sediments and the sand by weight ration 70:30. The present study may suggest the possible application of solidified sea bottom sediments into growth of other plants.