Biocolmation

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Biocolmation , also called biological colmation , is the reduction in the permeability of the soil through microbial biomass. The microbial biomass blocks the waterway in the pore space, forms an impermeable layer in the soil and thus reduces the speed of the infiltration of water.

Biocolmation is observed with continuous infiltration under various field conditions, for example in artificial water basins , percolation ditches , irrigation channels , sewage treatment systems and landfill barriers . It also influences the groundwater flow in the aquifer , changes the effectiveness of technical facilities such as a reactive wall or tertiary oil extraction . In situations where the infiltration of water is technically necessary, biocolmation can be problematic and require countermeasures such as regular drying of the system. In some cases, however, biocolmation can also be used to create an impermeable layer in order to minimize the infiltration rate and thus water loss.

general description

Change in permeability over time

Biocolmation manifests itself as a decrease in the infiltration rate. A reduction in the rate of infiltration in the technical experiment in this way was first observed in the 1940s, when the infiltration from water basins in irrigation systems and the water distribution on artificially irrigated agricultural soils were investigated. If the soils are continuously saturated with water, the permeability or the saturated hydraulic conductivity changes in 3 stages:

  1. Permeability decreases after 10 to 20 days, possibly due to physical changes in the soil structure.
  2. The permeability increases as the air trapped in the soil is displaced by the percolation water.
  3. The permeability decreases after 2 to 4 weeks due to the disintegration of aggregates and the biological colmation of soil pores with microbial cells and their synthesized metabolic products, for example extracellular polymeric substances such as polysaccharides .

Biocolmation is therefore involved in the third stage.

Causes of Impermeability

Depending on the field conditions, there are various causes for the change in hydraulic conductivity , of which biocolmation is only one.

  1. Physical causes: Physical clogging by suspended matter or physical changes in the soil such as the breakdown of the aggregate structure . The dissolution of the trapped soil air in the percolation water is also a physical cause, but here for the increase in hydraulic conductivity.
  2. Chemical causes: Change in the electrolyte concentration in the aqueous phase, which causes dispersion and swelling of clay minerals . A high concentration of sodium ions in the irrigation water leads to soil compaction via the exchange of sodium for magnesium or calcium; this is measured as the sodium adsorption ratio (SAR, Sodium Adsorption Ratio).
  3. Biological causes:
    1. Biocolmation by cells or cell colonies (such as bacteria , algae and fungi ) and substances synthesized by them such as extracellular polymeric substances that build up biofilms and hold cell colonies together are direct biological causes for the decrease in hydraulic conductivity. This is biocolmation in the narrower sense.
    2. The formation of gas bubbles, such as methane , which are formed through methanogenesis , displaces water from the soil pores and contributes to a reduction in hydraulic conductivity. Since the gas is a microbial end product, this can also be viewed as biocolmation.
    3. By converting soluble iron (II) ions into insoluble iron hydroxides, iron bacteria cause deposits of iron ocher precipitates, which can clog the soil pores. This is also an indirect biological cause of the decrease in hydraulic conductivity.

Individual evidence

  1. ^ LE Allison: Effect of microorganisms on permeability of soil under prolonged submergence . In: Soil Science . 63, No. 6, 1947, pp. 439-450.
  2. ↑ P. Baveye, P. Vandevivere, BL Hoyle, PC DeLeo, DS de Lozada: Environmental impact and mechanisms of the biological clogging of saturated soils and aquifer materials . (PDF) In: Critical Reviews in Environmental Science and Technology . 28, No. 2, 2006, pp. 123-191. doi : 10.1080 / 10643389891254197 .
  3. ^ RP Gupta, D. Swartzendruber: Flow-associated reduction in the hydraulic conductivity of quartz sand . In: Soil Science Society of America Journal . 26, No. 1, 1962, pp. 6-10. doi : 10.2136 / sssaj1962.03615995002600010003x .
  4. ↑ WT Frankenberger, FR Troeh, LC Dumenil: Bacterial effects on hydraulic conductivity of soils . In: Soil Science Society of America Journal . 43, No. 2, 1979, pp. 333-338. doi : 10.2136 / sssaj1979.03615995004300020019x .
  5. ↑ P. Vandevivere, P. Baveye: Saturated hydraulic conductivity reduction Caused by aerobic bacteria in sand columns . (PDF) In: Soil Science Society of America Journal . 56, No. 1, 1992, pp. 1-13. doi : 10.2136 / sssaj1992.03615995005600010001x .
  6. ↑ L. Xia, X. Zheng, H. Shao, J. Xin, Z. Sun, L. Wang: Effects of bacterial cells and two types of extracellular polymers on bioclogging of sand columns . In: Journal of Hydrology . 535, 2016, pp. 293-300. doi : 10.1016 / j.jhydrol.2016.01.075 .
  7. ↑ M. Gette-Bouvarot, F. Mermillod-Blondin, R. Angulo-Jaramillo, C. Delolme, D. Lemoine, L. Lassabatere, S. Loizeau, L. Volatier: Coupling hydraulic and biological measurements highlights the key influence of algal biofilm on infiltration basin performance . (PDF) In: Ecohydrology . 7, No. 3, 2014, pp. 950-964. doi : 10.1002 / eco.1421 .
  8. ↑ K. Seki, T. Miyazaki, M. Nakano: Reduction of hydraulic conductivity due to microbial effects . (PDF) In: Transactions of Japanese Society of Irrigation, Drainage and Reclamation Engineering . 181, 1996, pp. 137-144. doi : 10.11408 / jsidre1965.1996.137 .
  9. ↑ K. Seki, T. Miyazaki, M. Nakano: Effect of microorganisms on hydraulic conductivity decrease in infiltration . (PDF) In: European Journal of Soil Science . 49, No. 2, 1998, pp. 231-236. doi : 10.1046 / j.1365-2389.1998.00152.x .
  10. ^ Y. Jiang, S. Matsumoto: Change in microstructure of clogged soil in soil wastewater treatment under prolonged submergence . (PDF) In: Soil Science and Plant Nutrition . 41, No. 2, 1995, pp. 207-213. doi : 10.1080 / 00380768.1995.10419577 .
  11. ↑ SW Taylor, PCD Milly, PR Jaffé: Biofilm growth and the related changes in the physical properties of a porous medium: 2. Permeability . In: Water Resources Research . 26, No. 9, 1990, pp. 2161-2169. doi : 10.1029 / WR026i009p02161 .
  12. ^ L. Zhao, W. Zhu, W. Tong: Clogging processes caused by biofilm growth and organic particle accumulation in lab-scale vertical flow constructed wetlands . (PDF) In: Journal of Environmental Sciences . 21, No. 6, 2009, pp. 750-757. doi : 10.1016 / S1001-0742 (08) 62336-0 .
  13. ^ J. Kim, H. Choi, YA Pachepsky: Biofilm morphology as related to the porous media clogging . (PDF) In: Water Research . 44, No. 4, 2010, pp. 1193-1201. doi : 10.1016 / j.watres.2009.05.049 .
  14. ↑ K. Seki, T. Miyazaki: A mathematical model for biological clogging of uniform porous media . (PDF) In: Water Resources Research . 37, No. 12, 2001, pp. 2995-2999. doi : 10.1029 / 2001WR000395 .
  15. ^ WD Reynolds, DA Brown, SP Mathur, RP Overend: Effect of in-situ gas accumulation on the hydraulic conductivity of peat . In: Soil Science . 153, No. 5, 1992, pp. 397-408.
  16. ^ S. Houot, J. Berthelin: Submicroscopic studies of iron deposits occurring in field drains: Formation and evolution . In: Geoderma . 52, No. 3-4, 1992, pp. 209-222. doi : 10.1016 / 0016-7061 (92) 90037-8 .