Tutorial

Overview

SUTRA (SUbsurface TRAnsport) aka SSTR is a model to calculate the behavior of Organic MicroPollutants (OMPs) and microbial organisms (mbo) for 4 standard types of Public Supply Well Fields (PSWFs), which cover the most frequently occurring and most vulnerable groundwater resources for drinking water supply in the Netherlands (and Flanders). One of the aims of this approach is to forecast the behavior of new OMPs (or mbo’s) in groundwater. Groundwater is often overlooked in current environmental risk assessment methods, which are a priori or a posteriori applied when new organic chemicals appear on the market.

The 4 standard PSWF types consist of a phreatic, a semiconfined, a Basin Artificial Recharge (BAR) and River Bank Filtration (RBF) well field, each predefined with representative, standard hydrogeological, hydrological and hydrogeochemical characteristics.

This python version for OMP removal is based on the Lite+ version of the OMP transport model ‘TRANSATOMIC’ (acronym: TRANS Aquifer Transport Of MicroContaminants, developed by P.Stuyfzand) in which concentration changes are calculated with analytical solutions set in Excel-based TRANSATOMIC program by Pieter Stuyfzand.

The code for microbial organism removal is based on the equations given in chapter 6.7 of BTO 2012.015 “Gezondheidsrisico’s van fecale verontreiniging” [in Dutch], pp 71-74. The main mbo-removal equations are added to the Appendix.

Workflow

The model has been expanded to include Modflow (+ ModPath) solutions, in addition to the analytical solutions and to include advective microbial organism removal (‘mbo’) in addition to OMP removal.

The possibilties to calculate flow are:

  1. Calculate the travel time distribution along pathlines per aquifer zone (analytical approach: AnalyticalWell)

  2. Calculate the travel time distribution along pathlines per particle per model cell from start to endpoint (numerical approach: ModPathWell)

The possible pollutant types to calculate removal for are:

  1. Organic Micropollutants (omp)

  2. Microbial Organisms (mbo)

Any combination of travel distribution and removal of pollutants can be solved, as included in the examples.

Steps to follow

Operating the Sutra package typically involves several steps:

  1. Define the hydrogeochemical system (including PSWF type) using the HydroChemicalSchematisation class.

  2. Run either the AnalyticalWell or the ModPathWell class to calculate the travel time distribution along pathlines in the different aquifer zones.

  3. Obtain or enter removal parameters for omp (Substance class) or mbo (MicrobialOrganism class)

  4. Run the Transport class to calculate the removal and concentration in each zone (analytical) or along pathlines (modpath), and in the well

  5. Plot the desired functions

List of examples

Now, let’s try some examples. The initial solution will be supplied with additional commentary

  1. Travel time calculation using AnalyticalWell class, combined with ‘omp removal’ AW_omp_removal

  2. Travel time calculation using AnalyticalWell class, combined with ‘mbo removal’ AW_mbo_removal

  3. Travel time calculation using ModPathWell class, combined with ‘omp removal’ MPW_omp_removal

  4. Travel time calculation using ModPathWell class, combined with ‘mbo removal’ MPW_mbo_removal