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Bottom mud process
MSC Method
Prevention against bad odor
 Bad odor
 Malodorous substances in sludge
 Technology to suppress malodor
 Locations where bad odor occurs
 Odor control by the MSC method
 MSC Additive amount
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MSC method PJ
 Bottom mud process

Technology to suppress malodor

 MSC solving the bad odor problems on the waterside.

Bad odor

 Bad odor makes people unpleasant. Bad odor is caused by malodorous substances. The Offensive Odor Control Law specified the permissible limit of bad odor concentration on the atmosphere (Table-1).
 Odor is felt by humans' sense through smell. There are various types of odors related to indoor air, water supply and sewage water. However, there is no established measurement technology technique that can directly measure these odors.
 Bad odor is usually based on the combined action of such component and its density that makes the bad smell. Each of the substance and its situation is unfit to analyze the substance and its concentration that is causing the bad odor. This is indicated by a 6 scale made by trained professionals to appropriately define the odor intensity.(Table-2)
 In the Offensive Odor Control Law, the permissible limit of unpleasant odor in the atmosphere is between 2.5 to 3.5 concentration.

●The clarification of odor
・Aromatic odor   ・Vegetation odor   ・Soil and mold odor  ・Fishy odor
・Chemical odor  ・Metal odor  ・Septic odor  ・Unpleasant odor

Malodorous substance Odor sensation Permissible limit(ppm)
lower upper
 Ammonia  NH3  Irritating odor 1 5
 Methyl mercaptan  CH3SH  Smell like rotten onion 0.002 0.01
 Hydrogen sulfide  H2S  Rotten-egg smell 0.02 0.2
 Methyl sulfide  (CH3)2S  Smell like rotten cabbage 0.01 0.2
 Methyl disulfide  (CH3)2S2  Smell like garlic 0.009 0.1
 Trimethylamine  (CH3)3N  Smell like rotten fish 0.005 0.07
 Acetaldehyde  CH3CHO  Strong smell like wheat straw 0.05 0.5
 Styrene  CH2  Unpleasant smell like rubber 0.4 2
 Odor intensity 2.5 3.5

Odor intensity Odor Sensation
0  Odorless
1  Very weak (odor threshold)
2  Weak
3  Distinct
4  Strong
5  Very strong

Malodorous substances in sludge

 The cause of bottom mud accumulation is the direct inflow of sediments and/or the inflow of contaminated water containing organic matter and nutrients. The organic matter and nutrients after the inflow will continue to repeat dilution and diffusion, the bottom mud is then accumulated through precipitation. With elution and hoisting, some contaminated particles will regress back in the water. During this time, organic water is degraded by the aerobic bacteria that lives in the bottom of the water. Organic matter is then mineralized to nutrient salts (inorganic nitrogen and inorganic phosphorus state) and etc. In addition, the nutritive salts and carbon dioxide produced from mineralization will be absorbed by the phytoplankton and the growth of blue-green algae will progress thus contaminating the water quality. The dead bodies of phytoplankton through precipitation will accumulate in the bottom parts of the water, forming bottom mud.
 With the increase of large amounts of organic matter inflow and phytoplankton growth, the oxygen in the water is consumed causing the decrease of dissolve oxygen. In the bottom parts of the water, where there is no oxygen circulation it will make the bottom area in an anaerobic state that will cause the growth of anaerobic bacteria. The organic matter with the action of the anaerobic bacteria will become a malodorous substance such as hydrogen sulfide (H2S) and ammonia (NH3).
 Hydrogen sulfide is formed when the bottom part becomes anaerobic, it is contained on the accumulated bottom mud. Soluble in water, with weak acidity and its malodorous substance characteristic is a strong pungent odor similar to rotten eggs. And since it is trapped inside the bottom mud in a stationary state it hardly diffuses into the atmosphere but once it takes an impact from the outside it will diffuse.
 Ammonia is formed by organic matter decomposition in the bottom parts of the water that is in an anaerobic state and by the direct inflow of ammonia nitrogen (NH3 or NH4) from untreated sewage. Ammonia nitrogen when in water, if there is dissolve oxygen in the water it can be changed into nitrite (NO2) to nitric acid (NO3) by the nitrification action of the aerobic bacteria. But in the bottom part areas which has small amount of dissolve oxygen and without nitrification, ammonia stays as it is.
 Malodorous substances such as hydrogen sulfide and ammonia is contained sealed in the bottom mud and as long as they are in the bottom mud they will not diffuse into the atmosphere, but when it takes an impact from dredging and released in the atmosphere it will stink.

Technology to suppress malodor

 Current conventional deodorization technologies are as follows:

1.The removal of malodorous substances in the liquid
 Chemical treatment  Oxidation treatment  NaClO, H2O2, ClO2
 Metallic salt treatment  Zn salt, Fe salt
 Acid/alkali treatment  H2SO4、NaOH
 Physical treatment  Adsorption method
 Cooling method
 Dilution method
 Biological treatment  Enzyme microbial treatment
 Fungicide treatment

2.The removal of malodorous substances in the air
 Chemical treatment  Absorption method  Acid/alkali treatment  H2SO4、NaOH
 Oxidant treatment  NaClO、ClO2、O3
 Incineration  Direct removal, Catalytic burning
 Physical treatment  Adsorption method  Activated carbon, Zeolite
 Ion exchange  Ion exchange resin
 Sensory treatment  Masking method  Perfume oil
 Odor neutralization method  Vegetable essential oils, Green tea extract
 Biological treatment  Activated sludge method
 Soil deodorization method
 Biological odor control method

3.The methods
・The direct addition method is by directly adding a deodorizer to the substance and obtaining the direct reaction in the water.
・The dispersion method is by directly dispersing to the substance with a spreader.
・The spray method is by spraying fine mist deodorant in the air.

Locations where bad odor occurs

 The dredging+the transport of bottom sludge, pump dredging+mud water pipes, backhoe dredging or grab dredging+barge transportation method or air pressure transmission system pipes.

 With dredging work on the water surface, the pump dredging will not generate a bad odor because the bottom sludge is sealed through the pipes but with backhoe and grab dredging, the bad odor comes out as soon as the bottom sludge emerges out of the water and out into the atmosphere. Bad odor occurs even at the time of loading the sludge into the barge and transport.
 The sludge from the barge and the pipes are sent to a landfill, where it will be dehydrated and dried to a certain moisture content. However, since both the soil particles and the water are negative charge, it is difficult for them to separate, so it takes a lot of time to dry naturally and in the meantime, the bad odor will continue to occur.

Odor control by the MSC method

 The hydrogen sulfide (H2S)and ammonia (NH3)contained in the bottom mud is unpleasant to human beings, these are the malodorous substances specified in the Offensive Odor Control Law. These malodorous substances are formed from organic matter with anaerobic bacteria, the more organic matter in the sludge means more hydrogen sulfide and ammonia. The organic matter in the water is determined by measuring the indices of Chemical oxygen demand (COD) and Biochemical oxygen demand (BOD) that can confirm that the bottom sludge is organic.
 The main components of MSC are iron salt (mainly referred to as iron chloride (III) (ferric chloride): FeCl3) and metal salt (aluminum sulfate: Al2 (SO4) 3), strong acidic substances.These susbstances will react with the malodorous substance thus preventing the occurrence of malodor.

 In bottom mud dredging, the pump dredging method is suitable because the bad odor occurrs only on a few places. Bottom sludge suctioned by a pump dredger is diluted by adding water (dredging area water: sea or river water) and then sludge is transferred to disposal sites through desludging pipes. MSC are directly added and mixed to the sludge in the pipe with a stirring device.
 Since MSC is directly added in the sludge transportation pipe, it prevents bad odor on landfill disposal as well as transportation by barge ship. It prevents bad odor from each of the process.

 The main components of MSC are iron salt (mainly referred to as iron chloride (III) (ferric chloride): FeCl3) and metal salt (aluminum sulfate: Al2 (SO4) 3), strong acidic substances.These susbstances will react with the malodorous substance thus preventing the occurrence of malodor.
 Malodor prevention mechanism of MSC are as follows.

●Hydrogen Sulfide
 Hydrogen sulfide reacts with the aqueous solution containing metal ions, a property resulting in precipitation of the metal sulfide. Hydrogen sulfide is soluble in water, the aqueous solution is weak acidic, the precipitation product of sulfide, depends on the solubility product of the pH and sulfide. From these chemistries, the removal of hydrogen sulfide, oxidation and the metal salt treatment has been effective.
 MSC has metal ions with acidic substance, the hydrogen sulfide by oxidation action of chlorine ions as iron chloride (III) (Cl) is oxidized and decomposed, iron ions (Fe3+) will react with hydrogen sulphide sulfur ions (S2-), will become iron sulfide (FeS) insoluble and precipitate.With these chemical reactions, the hydrogen sulfide in the sludge will be decomposed and removed, prevents the occurrence of malodor.

 Ammonia is soluble in water, the aqueous solution of the alkaline substance pH changes its concentration. On Neutral range of pH7 ~ 8, ammonia is 1 ~ 2mg / L, with pH10, it will rise up to 20 ~ 30mg / L.
 These will make ammonia react in water and ables it dissociate NH3+H2O→NH4+ +OH- , by its acid that neutralizes alkaline, it will suppress the generation of ammonia.
 MSC has strong acidity, by adding it on the mud water it will neutralize alkaline, it will prevent the occurrence of ammonia malodor.

●Musty odor
 The musty odor found in detoriated water areas are caused by blue-green algae. The main causative agent of the musty of odor are the substances such as diosmin and 2MIB (methyl isoborneol) that is formed by the blue-green algae and actinomycetes. Algae uses the nitrogen and phosphorus in the water as their nutrient source, they will grow with the photosynthesis from the sunlight, by removing the nutritive salt, the occurrence of algae can be prevented so thus the occurrence of malodor.
 Dredging by the MSC method will suppress the elution of nutritive salt by removing the sludge. The dredging that will suck the bottom mud along with the contaminated water, will also remove the nutritive salt in the water. In addition, it will also directly remove the blue-green alage and the suspended solid, returning clear water. With the MSC method in water areas whereas the malodorous substance is removed, water environment is regenerated with high water transparency and without malodor.

MSC Additive amount

 The biggest advantage of the MSC method is the improvement of the soil and water contained in the organic bottom mud. The additive amount is determined by the soil amount and the amount of organic substance.
 Planning MSC additive amount, in the case of dredging, mud rate (soil rate, suspended solids SS) content contained in the mud water will be the additive MSC amount of respect to volume (m3) of (kg).
 Generally with dredging, the additive amount of MSC is the soil amount against the MSC solution that is [1.0 ~ 3.0kg / m3]. With mud water soil rate of 10% a small amount of [100 ~ 300g / m3] will improve the soil quality and the water quality of the separated water and at the same time it has been proven and highly evaluated to eliminate bad odor.

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