One can compare well clogging to cardiovascular disease: knowing the specific risk factors in advance helps reduce the probability of clogging and improves treatment of clogged wells. The Well-Clogging Risk Index is a tool to quantitatively estimate the risks of chemical well clogging, predominantly by iron(hydr)oxides on the well screen, and physical well clogging by particles on the borehole wall.

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The Well-Clogging Risk Index (WC-RI) tool yields a quantitative estimate of the risk of chemical well clogging, predominantly by iron(hydr)oxides on the well screen, and physical well clogging by particles on the borehole wall. By knowing the risk and type of well clogging, one can take specific preventive measures or, in the event of already existing problems, one can choose the right treatment method.

The tool leads you via 9 simple input screens to the final output screen (#10), where the resulting scores are shown. The scores consist of the following: the Risk of Chemical well clogging (RiC), the Risk of Mechanical well clogging (RiM), and a relative confidence indicator for both RiC and RiM. In addition, the score is given for each of 8-10 parameters which together determine RiC, RiM and their relative confidence indicator.

The advantages of this tool are the insight it provides into the risk of the two predominant forms of well clogging and their underlying factors, and the flexibility of dealing with fewer input data. The insight enables the choice of the correct preventive and curative measures. The flexibility means that the tool also works even when input data are lacking, in which case the relative confidence indicators decline accordingly. Moreover, sometimes hydrochemical data are not reliable, and should therefore be given less weight: the tool takes this into consideration.

The risk of well clogging is defined here as the chance (0-100%) that a cased, modern water-pumping well will clog during its expected, average lifetime of 50 years, to the point that it needs to be abandoned.

There are other forms of chemical well clogging, for instance by Al(OH)3, Mn3O4 and CaCO3, but these are relatively rare and not yet included in WC-RI. Biological well clogging is not discerned as a separate clogging type, but included under chemical or physical well clogging where it acts as a catalyser and contributor. Chemical well clogging of course does not exclude the simultaneous occurrence of physical clogging, and vice versa.

Manual

The risk of chemical well clogging by iron(hydr)oxides (ferrihydrite) is estimated by evaluating the kinetics of iron oxidation (dFe), the origin (Ori) of the raw groundwater abstracted by a well or well group, the well age (WA), the record of specific well yield (dQS) and entrance resistance (rER), the camera inspections (Cam), the analysis of total suspended solids (TSS), and the geochemical analysis of encrustations (Geo).
The chemical well clogging risk (RiC; 0-100%) is defined then as follows, together with a relative confidence RiCCONF (0-100%):

RiC = 100 {(dFe + Ori + WA + dQS) / NA}A {(rER + Cam + TSS + Geo) / NB}B (3.1)
RiCCONF = 100 (NA /4) (NB /4) (3.2)

where: { }A = score of chemical clogging rate [0-1]; { }B = indicator of chemical well clogging [0-1]; NA , NB = number of parameters in respectively { }A and { }B which had data to calculate RiC (max for each = 4).

The risk of mechanical well clogging by particles is estimated in a way very similar to that of chemical well clogging (RiC), that is, by evaluating the rate of mechanical clogging (VCLOG), the origin (Ori) of the raw groundwater abstracted by a well or well group, the well age (WA), the record of specific well yield (dQS), the risk of damage of the borehole wall (DAM), the record of entrance resistance (rER), the camera inspections (Cam), the analysis of total suspended solids (TSS), and the geochemical analysis of encrustations (Geo).

The mechanical well clogging risk (RiM; 0-100%) is defined as follows, together with a relative confidence RiMCONF (0-100%):

RiM = 100 {(VCLOG + Ori + WA + dQS + DAM + SORT) / NC}C *
{(rER + Cam + TSS + Geo) / ND}D (3.3)

RiMCONF = 100 (NC /6) (ND /4) (3.4)

where: { }C = score of mechanical clogging rate [0-1]; { }D = indicator of mechanical well clogging [0-1]; NC , ND = number of parameters in resp. { }C and { }D which had data to calculate RiM (max 6 for { }C and 4 for { }D).

When data on any of the 8 parameters in Eq.3.1 or 10 parameters in Eq.3.3 is lacking, then its value is set at 0, and N in Eq.3.2 and 3.4 is reduced by 1. This allows RiC and RiM to be determined despite the lacking data, which however results in a decreased relative confidence.
Further details on the calculation and scoring of the 8-10 parameters will be shortly provided in a separate document.

Software

The tool leads you via 9 simple input screens to the final output screen (#10), where the resulting scores are shown. After completing these screens successively, with option to go back to the previous one, you can click on any screen number to go to it directly.

If no data are available on a specific parameter, this is not a problem, do not enter anything and simply proceed to the next step.

Since the tool yields nearly immediate results, a stand-alone version is not required.

Training

The Well-Clogging Risk Index tool is very simple to use and probably does not need any support. Nevertheless, there are several forms of support available to ensure that you optimise your use of the tool, and that you are updated on all the latest developments. Specifically, you can make use of the following options to suit your particular situation:

  • Expanded or modified functionalities to create tailored solutions.
  • Consultancy services, for instance, regarding the interpretation of the clogging risk index, and the measures to prevent or cure well plugging.

Publications

The Well-Clogging Risk Index is based on about 40 years of research by KWR (and others) on the design, clogging, management and operation of pumping wells, mainly for drinking water supply. See references listed below.

  • Bustos Medina, D.A., G.A. van den Berg, B.M. van Breukelen, M. Juhasz-Holterman, P.J. Stuyfzand 2013. Iron hydroxide clogging of public supply wells receiving artificial recharge: Near-well and in-well hydrological and hydrochemical observations. Hydrogeology Journal 21(7), 1393-1412.
  • De la Lomo Gonzales, B. and C.G.E.M. van Beek 2013. Evaluation of well clogging and well field management Heel, after 10 years artificial recharge. KWR report.
  • De Zwart, B.R. 2007. Investigation of clogging processes in unconsolidated aquifers near water supply wells. PhD TU Delft, 200 p.
  • Houben, G. & C. Treskatis 2007. Water well rehabilitation and reconstruction. McGraw-Hill, NY USA, 391p.
  • IF Technology [red.] 2006. Voorkomen en verwijderen van putverstopping door deeltjes op de boorgatwand; richtlijnen voor ontwerp, realisatie, bedrijfsvoering en regeneratie van pompputten. Uitgave Kiwa WR Nieuwegein, 69p.
  • Kobus, E.J.M. & W.J. Vlasblom 1975. Putverstopping door ijzerneerslagen te Castricum. Kiwa-Mededeling, 38, 52p.
  • Makkink, H.J., M.L.M. Balemans, E.J. Schrama, I. Leunk, F. Rambags 2011. Kennisdocument Putten(velden); Ontwerp, aanleg en exploitatie van pomp- en waarnemingsputten; update 2011. KWR Rapport, KWR 2011.014.
  • Raat, K.J., I. Leunk and H. Beverloo 2008. Particle concentrations in chemically clogged wells following on and off switchings; results from three wells in Berlin, Germany. KWR report, KWR 08.065, 19p.
  • Schwarzmüller, H. (ed.) 2009a. Extended summary Project acronym WellMa1. Kompetenz-zentrum Wasser Berlin gGmbH, 46p.
  • Stuyfzand, P.J. 2007. Naar een effectievere diagnose, therapie en preventie van chemische put- en drainverstopping. H2O 2007-8, 44-47.
  • Timmer H., Verdel J.D., Jongmans AG (2003) Well clogging by particles in Dutch well fields. J Am Water Works Assoc 95 (8):112–118
  • Van Beek, C.G.E.M., R.J.M. Breedveld, M. Juhász-Holterman, A. Oosterhof & P.J. Stuyfzand 2009. Cause and prevention of well bore clogging by particles. Hydrogeology Journal 17, 1877-1886.
  • Van Beek, C.G.E.M. 2010. Cause and prevention of clogging of wells abstracting groundwater from unconsolidated aquifers. PhD VU University, 203p.

Tool Expert(s)

Pieter Stuyfzand

Pieter Stuyfzand

Principal scientist, KWR

+31(0)30 60 69 552
Pieter.Stuyfzand@kwrwater.nl