Overview

Principles of environmental science and engineering (Engr233 / NSci323) teaches the fundamental physical, biological, and chemical principles of environmental processes. The course applies mathematics and science to environmental problems with a focus on the provision of safe drinking water and the proper treatment of wastewater. Additionally, the course discusses the application of major Federal environmental laws in the regulation of pollutants. This course is co-listed with NSci 323. The course meets the following program outcomes

Course learning outcomes for Engr233 / NSci323 are as follows:

SLO1: Use modern scientific software in environmental analysis, design, and communication of results (10-points)

Successfully knitting this Rmd file, updating the author name, and providing neat professional output is worth up to 10-points.

SLO2 Federal environmental laws in the regulation of pollutants and contaminants to protect human and environmental health. (20-points)

Please refer to the EPA National Primary Drinking Water Standards website, your lesson sheets, and the Tri-county/Mni Waste’ Rural Water System Consumer Confidence Report to answer the following questions.

  1. (4-points) Explain the difference between SDWA primary and secondary standards and provide an example of each.

The difference between a Primary and secondary standards is that the primary standards are used to limit the contaminants and make the drinking water safe. It is put into place for the health of the people, while secondary standards put into place to make the drinking water look ascetically pleasing or make the drinking water taste better.

  1. (2-points) Explain the significance of Maximum Contaminant Levels (MCLs) and Maximum Contaminant Level Goals (MCLGs) in the context of the Safe Drinking Water Act.

Maximum Contaminant levels is measurement that allows for drinking water to be potable. Maximum Contaminant level Goals is a measure ment that EPA and everyone wants to aim for in an ideal world.

  1. (2-points) Name three classes of contaminants regulated under the Safe Drinking Water Act.

Three classes of contaminant are Inorganic chemical, Organic chemicals and Disinfection Byproducts.

  1. (8-points) For each of the three classes provided above: i. Identify a contaminant, ii. identify whether it is regulated as a Maximum Contaminant Level (MCL) or Treatment Technology (TT), iii. describe its potential health effects due to long-term exposure, iv. identify a potential contaminant source.

Copper is regulated as a Treatment Technology, its potential long term exposure is liver or kidney damage, and the potential contaminant source is corrosion of household plumbing systems and erosion of natural deposits. Hexachlorocyclopentadiene is regulated as an MCL, the potential health risks for contaminant are kidney or stomach problems, and the potential contaminant source is discharge from chemical factories. Chlorite is an MCL, health risks are anemia, and nervous system effects in infants and young children, and source of contaminant is a byproduct of drinking water disinfection.

  1. (4-points) Name two contaminants in Mni Waste’ drinking water that exceed the MCLG. Do any of the contaminants listed in the Tri-county/Mni Waste’ Rural Water System Consumer Confidence Report exceed the MCL?

Arsenic and Total trihalomethanes both exceed the MCLG, but I do not see any contaminants that exceed the MCL.

SLO3 Implement a systems approach to environmental problems through the application of mass balance and chemical equilibria principles. (40-points)

Please answer the following questions about the pH, electroneutrality, and characteristics of four regional groundwaters by running the code below and referring to the laboratory reports provided to answer the following questions. Reach out to me if you are having trouble with the code

  1. (4-points) What is the hydrogen ion concentration for the PRR municipal water lab report pH?

  2. (4-points) Would addition of a small amount of strong acid affect the pH of PRR municipal water based on the alkalinity reported in the lab report? Why or why not?

It may because it is considered a mixed type that is almost a strong acid according to the Piper diagram.

  1. (4-points) What is meant by electroneutrality? Run the code below and check the wat_data_summ tibble. Describe the results. What, if anything, is missing from the laboratory analysis?

Electroneutrality is when the amount of anions and cations are the same. The electroneutrality for Madison, Minnelusa, and Mni Wiconi southern PRR is about neutral, but the Cherry Creek electroneutrality’s standard devation is -3.95.

  1. (10-points) Describe the types of water based on the Piper diagram results (below) for the four water samples.

Mni Wiconi is a mixed type that is a sodium and potassium cation and a bicarbonate type anion. Cherry Creek Artesion is a sodium chloride type, sodium and potassium cation, and bicarbonate anion. Minnelusa is a magnesium bicarbonate type, calcium type cation, and a bicarbonate type anion. Madison is a magnesium bicarbonate type, calcium type cation, and a bicarbonate type anion.

  1. (4-points) Describe each of the waters on the basis of their TDS. Are any of the waters not suitable for drinking water? Why or why not?

Madison, Minnelusa, and Mni wiconi are all considered good. Madison is very close to being considered excellent and Mni Wiconi is close to being considered fair. The Cherry Creek artesian is 5526 and is unacceptable. It exceeds a TDS of 1200.

  1. (10-points) Describe the hardness of each of the waters based on the hardness bar chart (below). Is the hardness temporary (carbonate) hardness or permanent hardness?

Madison and Minnelusa have a temporary hardness and treamtent can be used to soften the water. Mni Wiconi is a mixed type, but treatment can still used to soften the water. Cherry Creek has permanent hardness and will be too expensive to soften.

  1. (4-points) What are two possible treatment technologies to remove hardness from water? Discuss advantages and disadvantages to each.

Reverse Osmosis reduces cations in water and reduces 98% of incoming minerals from the water. The disadvantage is that the equipment is more expensive, and the cost per a gallon is higher about 3- 4 gallons of water are thrown away to make a gallon of RO. Using zeolite is a another way to soften water, but afterwards it has no real use.

SLO4 Demonstrate the concept of risk in relation to environmental standards. (20-points)

Please answer the following questions about risk using your lesson plans, text, and notes.

  1. (4-points) Discuss the ethical considerations involved in setting environmental standards based on risk assessment. How do different stakeholders’ perspectives influence these standards?

There are several ethical considerations that are involved with setting enviromental standards, because the persception of what people may say. Policy-makers and politicians should use factual data to support necessary standards rather than using one’s own perceptive.

  1. (2-points) What are some potential ways policy-makers can reduce differences between an assessed risk and a perceived risk for a community?

Policy-makers can use factual data that goes along with the assessed risk and use wording that makes the perception of risk less daunting because the perception of risk is as real as the scientific perspective of risk in a public health context.

  1. (4-points) How do cost-benefit analyses factor into the establishment of environmental standards in relation to identified risks?

There is no amount of money that can reduce all risk, but there are ways to reduce the risk of exposure.

  1. (2-points) What are the four steps in risk assessment as described by the National Academy of Science.

1.)Hazard dentifcation 2.) Dose-response assessment 3.) exposure assessment 4.) risk characterization

  1. (6-points) Distinguish between risk management and risk assessment. What are two challenges in managing environmental and human health risks?

Risk assessment is the likelyhood of harm that is caused by exposure or the dose taken in by a person. Risk management is what to do about the exposure. The challenge of risk management is making decisions under extreme uncertainty about how to allocate national resources to protect public health and environment.

SLO5 Describe municipal and rural water and wastewater treatment processes. (10-points)

Please answer the following questions about drinking water assessment and treatment using your lesson plans, text, and notes

  1. (5-points) The Mni Wiconi and Mni Waste water systems rely in whole or in part on treated Mnisose surface water. Rights to this water are established under the Treaties. Please briefly describe the typical steps involved in surface water treatment.
  1. Screen and grit removal take out large floating and suspended debris. 2. Primary sedimentation removes the particles that will settle out by gravity. 3. rapid mixing and coagulation use chemicals and agitation to encourage suspended particles to collide and adhere into larger particles. 4. flocculation, which is the process of gently mixing the water. encourages the formation of large particles of floc that will more easily settle. 5. secondary settling slows the flow enough so that gravity will cause the floc to settle. 6. filtation removes particles and floc that are too small or light to settle by gravity. 7. sludge processing refers to the dewatering and dispostion of solids and liquids collected from the settling tanks. 8. Disinfection contact provides sufficient time for the added disinfectant to inactive any remaining pathogens before water is distributed.
  1. (5-points) The Mni Wiconi water system relies in part on groundwater from the Arikaree Formation. Please briefly describe the typical steps involved in groundwater treatment.
  1. Aeration removes excess and objectionable gases.
  2. Flocculation follows chemical addition, which forces the calcium and magnesium above their solubility limits.
  3. Sedimentation removes the hardness particles that will now settle by gravity.
  4. Recarbonation readjusts the water pH and alkalinity and may cause additional precipitation of hardness-causing ions.
  5. Filtration, disinfection, and solids processing serve the same purposes as for surface water.

Code to visualize water characteristics using a Piper diagram and a bar chart

Data description

Data for the Rapid City drinking water is estimated from the USGS report “Water-quality characteristics in the Black Hills area, South Dakota” https://pubs.usgs.gov/wri/wri014194/ – abstract https://pubs.usgs.gov/wri/wri014194/pdf/wri014194.pdf – direct download link

Other data are from laboratory reports for a deep groundwater at Cherry Creek, SD and a municipal drinking water from the Mni Wiconi project. The Mni Wiconi water is a blend of treated surface water from the Missouri River and groundwater from the Arikaree Formation.

Updates from in-class code

  1. Added in the F, Br, I, and nitrate ions but still had missing anions

  2. Found adding Si as an anion for USGS data substantially improved electroneutrality see: https://snowpure.com/docs/resintech-silica-iwc99.pdf

Get and munge data

Plot piper diagram

Prepare and plot hardness diagram

Appendix 1: Bicarbonate - carbonate equlibrium

The code chunk 05_below calculates the equilibrium concentration of carbonate as a function of hydrogen ion concentration – the pH of the water. This is described in detail on pages 67 and 68 of the text.

For nearly neutral water (pH between 6 and 8.5), the concentrations of \(CO_3^(2-)\) and \(OH^{-}\) ions are very small. In this same pH range, the bicarbonate/carbonate equilibrium strongly favors bicarbonate. The alkalinity is approximately equal to \((HCO_3)\)

In the equation below, bicarbonate dissociates to release a hydrogen ion and a carbonate ion

\[ \mathrm{HCO}_3^{-} \rightleftarrows \mathrm{H}^{+}+\mathrm{CO}_3^{2-} \]

The equilibrium between bicarbonate and carbonate is written as: \[ \frac{\left[\mathrm{H}^{+}\right]\left[\mathrm{CO}_3^{2-}\right]}{\left[\mathrm{HCO}_3^{-}\right]}=K_2=4.68 \times 10^{-11} \mathrm{~mol} / \mathrm{L} \]

where \(K_2\) is constant describing the second dissociation of carbonic acid

\[H_2CO_3 \rightleftarrows CO_{2}\mathrm{(aq)} + H_2O\]

This is the equation to transform concentration as an equivalent as CaCO3 \[ \mathrm{mg} / \mathrm{L} \text { of } \mathrm{X} \text { as } \mathrm{CaCO}_3=\frac{\text { concentration of } \mathrm{X}(\mathrm{mg} / \mathrm{L}) \times 50.0 \mathrm{mg} \mathrm{CaCO} / \mathrm{meq}}{\mathrm{EW} \text { of } \mathrm{X}(\mathrm{mg} / \mathrm{meq})} \]

The total hardness (TH) is the sum of individual hardness components \[ \text { Total Hardness (TH) }=\mathrm{Ca}^{2+}+\mathrm{Mg}^{2+} \]

Total hardness can be separated into two components: carbonate hardness (CH), which associated with \((CO_3)\) and \((HCO_3)\), and noncarbonate hardness (NCH) associated with other anions.

If the concentration of \((CO_3)\) and \((HCO_3)\) equals or exceeds the total hardness (if alkalinity exceeds TH), then CH = TH

If alkalinity is less than TH, then CH = alkalinity and NCH = TH - CH