This is the main page for the water-quality monitoring team project for the UMass Public Science Maker class.

Objectives

1. Create a durable WQ monitoring device using an Arduino
2. Use device to monitor WQ of the Tan Brook Watershed

Background

Motivation

Surface water quality has direct impacts on human and ecosystem health, and is increasingly impaired from urban runoff, agriculture, industry, and other human activities. Because of the analytical methods required, water-quality monitoring has historically been expensive, and as a result data coverage in time and space has been sparse. Recent improvements in sensor and computing technology have driven down these costs, to the point where active DIY communities have developed around building WQ-monitoring devices. A few such devices are outlined in the Existing Devices section below.

Tan Brook, Amherst, MA

The Tan Brook Watershed is part of the overall Connecticut River watershed. It runs from its headwaters north of Strong Street and west of Wildwood Cemetery past Wildwood elementary school, Amherst junior high, Amherst Regional High School, and flows north into the Campus Pond at the University of Massachusetts, Amherst. The water continues to flow west towards the Mullins Center before it finally empties into the Mill River.

The brook is essentially an underground system of culverts that convey storm water runoff from town buildings and roads into the UMass Campus Pond. Despite the vast area the Tan Brook watershed covers, being situated underground makes it relatively unheard of and unidentifiable on maps.

Despite their practicality for the implementation of infrastructure, the culverts of Tan Brook have been the cause of increased flooding in the watershed area, increased inflow of pollutants from lawns, impervious surfaces, and an overall degradation of the stream water quality.

Residents of Fearing Street, North Pleasant Street and Triangle Street have frequently reported flooded basements Local residents have also reported strong chemical/gasoline odors emanating from the small day-lighted section of the brook located north and south of Fearing Street. Chemical dumping from local tanneries into the stream in the 1820s was commonly practiced, also raises concerns for locals.

With our device, we will be able to monitor the concentration of dissolved solids in the brook.

Existing Devices

Riffle

The Riffle is an open-source conductivity (and temperature?) meter and is a collaborative project from the OpenWater PublicLab initiative. The Riffle is currently under active development, and has at least one spinoff version, the riffle-ito. Future additions may include fluorescence, turbidity, and pressure capabilities.

Riffle-ito

Don Blair's Riffle-ito is a version of the Riffle implemented on Arduino. It is "higher cost and lower functionality" than the Riffle, but is more modifiable thanks to its base hardware. A list of parts with prices is given in this spreadsheet.

Our Device

We will begin by implementing the Riffle-ito. If all goes well (and quickly) we can explore adding sensors beyond the thermistor. UV-254 (for organics) and turbidity seem like good candidates.

Progress so far

Connecting thermistor to Arduino (10/7/14)

We applied 5 volts across a 10k resistor and thermistor in series, measured voltage across thermistor only. Then used Steinhart-Hart equation to convert the thermistor resistance to temperature. This was done by modifying the riffle-ito arduino script from the riffle-ito github repository.

thermistor help page for arduino

We got some temperature readings! Thanks to Arduino help from Varun Srinivasan and an old-fashioned physical thermometer, we verified the accuracy (within ~0.1 degrees C) of the thermistor.

Measuring electrical resistance using an audio jack (10/8/14)

We replaced the thermistor with an amputated set of headphones, turning the audio jack into a conductivity probe. This idea came straight from the Riffle webpage, and we used this tutorial on instructables to figure out how to get the left and right leads into our Arduino breadboard. And it works! It needs calibrating, but that should be straightforward.

Next steps:

1. modify circuit to calculate temperature and conductance simultaneously
2. Calibrate conductivity meter to conductivity standards, adjust for temperature
3. Obtain housing (PVC pipe?)
4. Figure out data logging
5. Add functionality to measure turbidity (?) using photoresistor or photodiode and LED

Notes and findings

Exploring riffle-ito github repository

Downloaded Cadsoft Eagle to view schematic files

hardware/* directory:

• CSVs
• datalog4.csv: apparently containing output WQ data
• riffleito-CTD-REVA.csv, riffleito-KAP-REVB.csv, riffleito-REVC.csv, riffleito-REVD-partslist.csv: unclear (apparently last is a parts list); strange formatting
• reference to 555 circuits--apparently reference to a timer (see wikipedia article)
• .brd, .sch files showing various circuit boards, most don't appear to be arduinos.

software/* directory

• single .ino file: dwbThermistorRtcSD1LowPow6.ino
• Well-documented, not taking time to read through now, but should later.
• otherwise, only library files. Hopefully I don't need to learn much about these to use them.

Resources online

Found a Riffle presentation from pvos github group. (riffleito/riffle-present) Lots of good info in it.

Also worth reading through issues on riffle-ito github page - (in link #24 on conductivity measurements) a link to this article on Conductivity Theory and Practice - (in link #22) "The ~ 18 mm width of the riffle-ito fits snugly inside 3/4" Schedule 40 PVC pipe. There are simple 'screw plugs' that can be attached to the ends of the PVC, and which would allow for the batteries / device to easily be removed -- for now, I was only able to source the rounded end-caps. Ideal configuration might be to have one of these end-caps on one end (with holes drilled for temp and conductivity probes), and the screw-cap on the other."