Section outline

    • Definition in industrial wastewater test method

      Suspended Solid, SS

      Substance passing through a 2 mm filter

      Substances that remain on a filter with a pore size of 1 mm

      Dissolved Matter, DM

      Substances that pass through a filter with a pore size of 1 mm

      *Suspended solids are abbreviated as “SS” below.

    • Typical SS separation method

      Filtration

      Flocculation

      Centrifugation

      Cyclone

    • SS aggregates with increasing salt concentration

      川から流入した泥土が沿岸で凝集・沈殿しています。

      Mud that flows in from the river is coagulating and sedimenting along the coast.




    • SS industrial wastewater standards

      •Kobe：40 mg/kg

      •Kawasaki・Yokohama：70 mg/kg

      •Tokyo：120 mg/kg

      •Nagoya・Hakodate：200 mg/kg

      •Sapporo：300 mg/kg

      The reason why the standard values ​​differ depending on the region is that there are "uniform wastewater standards" set by law by the country and more stringent "additional wastewater standards" established by each local government.

    • Electric double layer that creates repulsive force between SS particles

      電気的に反発する微粒子は、凝集せずに安定に分散：Electrically repulsive particles are stably dispersed without agglomeration

      電気二重層：electric double layer

      電気的反発が及ぶ距離：Distance of electrical repulsion



    • surface charge of suspended solids

      Marshall, Aust. H. Biol. Sci. (1967) 

      Huang & Lin, Adsorption from aqueous solutions (1981)

      正電荷：positive charge　負電荷：negative charge　微生物：microbe　泥粒子：biofluid

      ほとんどのSSが中性で負に荷電：Most SS negatively charged when neutral.

    • silica SiO₂ (It is the same substance as the silica gel of the desiccant.)

      dry state

    • the case of silica, SiO₂

      state of absorbing water

      Hydrogen ions dissociate in water and silica has a negative charge.

    • Mechanism of flocculation

      Mechanism of action of polymer flocculants

       

      高分子凝集剤：high polymer agglutinate

      微粒子と逆の電荷をもつ高分子(凝集剤)を加えると粒子表面に吸着し、凝集剤が微粒子を架橋し大きな凝集体を形成して速やかに沈降します。：When a polymer (flocculant) with an opposite charge to that of the particles is added, it is adsorbed onto the particle surface, and the flocculant cross-links the particles to form large aggregates that settle out quickly.


    • Development of biodegradable flocculants

      ＜Conventional flocculant＞

      Inorganic: PAC, aluminum sulfate, iron sulfate, etc.

      Organic: polyacrylamide, etc.

      ＜problem＞

      Carcinogenicity of Unreacted Monomers in Polyacrylamide

      Aluminum inhibits plant root growth

      ↓

      Development of biodegradable flocculants that are safe for living organisms and the environment

      ＜Efforts of our laboratory＞

      Development of "biodegradable flocculant" using protein as raw material

      Raw materials include chicken egg whites, milk, soybeans, scallop processing waste, etc.