5.Conclusion

5.Conclusion

It was recognized that there was possibility the organically polluted bottom sediments to be improved by use of the bio- reactor. Test results showed that the improved bottom sediments might restrain the generation of COD, nitrogen and phosphorus that caused eutrophication. The test results would apply to below are the improved sediments, reduction of pollution, treatments of spill water and rot order in the experiments.

5.1 Improved Bottom Sediments

Improved sediments treated by the biological treatment has a color of light brown and no rot odor.
With respect to reduction of the polluted bottom sediments, addition of the activated sludge and acclimation conditions should be considered as well as retention time and aeration intensity.
Volatile solids ratio VSS/SS of the improved bottom sediments increased in comparison with the bottom sediments.
ORP of the improved bottom sediments is between 450 and 520 mV.
Nitrogen causes inorganic feature, nitrification and de-nitrate reaction.
Phosphorus is stabilized by metals and oxidation and reaction occurred in the bottom sediments, and the release of phosphorus into the water is restrained.
Improved bottom sediments retains a large amount of oxygen which is generated by oxidation of metal substances iron, etc. in the sediments, and will be useful for the improvement of the bottom sediments condition.
Improved bottom sediments contains bacteria 1,050/cc and coliform group 230 groups 230 groups/cc which restrain malignant bacteria._

5.2 Volume Reduction of the Bottom sediments

Test realest which the activated sludge was added, shows reduction effect of the volume of the polluted bottom sediments.
Test result which the activated sludge was not added, observed no reduction effect of the volume.
Reduction ratio of the bottom sediments in No.2 water tank was 33% after 30days and 58% after 75 days.
Reduction rate in No.2 water tank was from 0.7 to 1.0 SS%/d.
Reduction rate in the No.2 water tank was from 600 to 400 SS mg/l/d.
Reduction tendency of the bottom sediments in No.2 water tank was observed in volatile solids. VSS.
Reduction would be effected by the quality of the bottom sediments, retention time, aeration intensity, and characteristics and amount of the activated sludge applied.

5.3 Odor

The bottom sediments smelled rot order like an addled egg.
Rot odor caused in each testing water tank was vanished in a few days after the biological treatment.
Spillwater in each tank has no rot odor.

5.4 Spillwater treatments

Since marsh Furukawa classified as B type, it will able to improve the Spillwater quality, treating COD, SS, T-N and T-P contained in it.

5.5 Prospects

It is considered that the technique experimented on the treatments of the bottom sediments will be applicable in case of extremely difficult to get disposal area of the dredged bottom sediments. But the object bottom sediments applying this technique is only for the bottom sediments which highly contained organic properties, while excluding the treatments of the bottom sediments contaminated by heavy metals. This is the first experiments for the bottom sediments to have been treated to improve by using bio-reactor, but there are many problems awaiting solution, it is needed to repeat tests and analyses over and over again.

Problems as below.

Preparation of a guideline to improve bottom sediments by the biological treatment.
In case of returning the improved bottom sediments into the marsh, it should be analyzed for bioassay how affect the ecosystem of the marsh.
Development of technology and equipment for the improved bottom sediments back into the marsh by means of spraying it with equipment.
Establishment of energy saving technology for bio-reactor treatment