# The New River Wetlands

Their role in removing bacteria from the river water

# The New River

• The New River has been constantly called the “most polluted river in the United States. Running 66 miles from the US - Mexico border to the Salton Sea, Flow at the border is approximately 200 ft3/s (6 m3/s ), and about three times this flow at the Salton Sea because of agricultural discharges in the Imperial Valley. • The pollution of the river comes from chemical runoff from the agricultural waste of the Imperial Valley irrigation system that accounts for about (69.6%), 29% is sewage from Mexicali, and waste from manufacturing plants is 1.8%. • By the time the river crosses the border, it carries about 100 different identified contaminants, such as volatile organic compounds, heavy metals, (like selenium, uranium, arsenic, and mercury), pesticides, and many types of pathogenic organisms that cause tuberculosis, cholera, encephalitis, and typhoid. Fecal coliform bacteria has various levels ranging from 100K to 16million colonies per milliliter, and this is far above the US Mexico treaty limit of only 240 colonies.

# History of Pollution

• Because of the sewage waste, the New River has had large amounts of the bacteria E. Coli since the early 1940s. The Water Treaty with Mexico that solved the problem of the Colorado River water uses included the agreement that both countries had to concentrate primarily on sanitation problems along the border, and the two countries created the International Boundary and Water Comission and in 1948 this commision decided that they had to build a facilitiy to treat the water of the New River at a plant in Calexico. • After the Mexicali boom in population in the 1960s, and the increasing numbers of assembly plants after the NAFTA treaty of 1990, the old water plants in Mexicali and Calexico were inadequate to treat all the water flowing into the New River. • In the last years, there have been numerous attempts to control the pollutants in the New River. After the State Senate Bill 387 which amends state law to protect human and the natural environment, there are new hopes for the creation of more plants and other methods to reduce the amount of pollutants and, especially, the E. Coli Bacteria. Foam caused by toxic waste flows wi th the New

R iver water as it crosses the border.

# What are the “pathogens” in the

New River?

• Pathogens (from the Greek pathos “suffering/emotion” and gene “to give birth to”) are biological organisms that cause illness and infectious diseases. These pathogens are more easily measured by bacteria called Coliforms, which are rod - shaped, gram - negative, non - spore forming organisms that are abundant in the feces of warm - blooded animals. They are used to measure the presence of other pathogenic organisms in a certain environment such as virus, protozoa, or parasites.

# Attempts to Clean the New River

• There have been many attempts to “clean” the New R iver by m any groups of “concerned” local citizens and local governmental agencies such as the Calexico New

R iver Committee in 2001, the Salton Sea Ecosystem Restoration program, and the Citizen’s Congressional Task Force on the New R iver.

• A proposal from the Citizens Congressional Task Force on the New R iver wa s to construct a series of wetlands that would act as “nature’s filters” to remove the bacteria and the other contaminants carried by the river’s water. The project was finally funded by the U.S. Environmental Protection Agency and the Bureau of Reclamation. • The purpose of the construction of wetlands wa s not to create a w ildlife habitat but to demonstrate the ability of wetlands to improve the quality of wa ter in the New

R iver.

# Wetlands

• Wetlands have been constructed in developed nations to treat water that contains industrial, agricultural, and residential waste. These wetlands act as natural filters where the contaminants are removed through a series of natural processes involving wetland plants and a network of causeways that decrease these contaminants as the water reaches the outlet and is returned to the rivers.

• Brawley Wetland Imperial Wetland

• Two wetlands were constructed in 2000, one near Imperial and another one near Brawley, with the Imperial wetland receiving agricultural waste water and the Brawley wetland receiving water directly from the New River.

# Proposal

• As wetlands have been proven to be effective in other environments, the proposal of the construction of a series of wetlands attempts to reduce significantly the percentages of contaminants of the New River. If the wetlands of Imperial and Brawley demonstrate such outcome, there is a solid consideration for future wetlands being constructed. In order to measure the effects of the wetlands on the quality of water, a study of monthly samples were taken in the inlets and outlets of the wetlands from January 2001 to January 2007.

# How wetlands work with the

environment

• Regarding removal of bacteria and other pathogenic organisms, wetlands wo rk in different ways, • Predation: most bacteria are food for other organisms, such as nematodes, rotifers, and protozoa.
• Solar Disinfection: the solar UV rays are a powerful means of killing bacteria after it has been in the wetlands for several days.
• Mortality: most bacteria die in we tlands after several days, depending on the type of bacteria and the conditions of the water.

# Measuring effectiveness of bacteria

removal

• Samples of the New River water were collected before reaching the Brawley wetland (inlet) and then after the water left the wetland (outlet) with samples of Total Coliforms numbers per 100 milliliters ( # per 100 ml) in a 50 - month period from January 2001 to January 2005.

# Percentages of Total Coliform

reduced

• We can also form a graph of the percentages of Total Coliform reduced each month by using (((Outlet#)*100)/(Inlet#)). This graph takes the form,

• This graph surely looks different to the other graphs since we are dealing wi th percentages and not w ith the actual numbers of Total Coliforms in the wa ter.

# Numbers of Total Coliform reduced

• We can think of the graph ((# in Inlet) - (# in outlet)) as the numbres of Total Coliform reduced or eliminated from the New River water which takes the form,

# How **to construct a function of the data** 

• In statistics, after you have a valid set of data that you obtained from experiments, you can use that data to construct a function. This function will help you estimate and predict values that you don’t have in your set of data.
• For instance, if you have

You can find the function of these points in a way that you will get

# Methods

• Interpolation You can create a curve to estimate the value of x in other points that you don’t have yet on your set

• Linear Interpolation This is the easiest method, you just have to joint each point that you have by finding the slope and getting a linear equaiton for each segment between points,

• Polynomial Interpolation There are many algorithms available that help you find a polynomial of degree n if you have n points on your graph,

• Extrapolation This is the process of finding new data points beyond the existent data points. This is the method that you would like to use if you want to predict a future estimate,

# Analyzing numbers of Total

Coliform reduced

• When measuring the effects of the wetlands, we basically want to analyze the numbers of Total Coliform reduced.
• We can take this graph and attempt to find an estimated polynomial of the graph using Newton’s Divided Difference that calculates the coefficients of the polynomial using the x - axis(time) and y - axis(# per 100ml). The method looks something like this, If, Then,

# Predicting Future Reductions

• Using only 10 months as samples, the polynomial that we can use to predict future reductions in the water is, with x as the number of months from January 1, 2001, is of the form, 

### 700+5725(x - 1) - 85(x- 1)(x- 5) - 79.071(x - 1)(x- 5)(x10)+30.867(x - 1)(x- 5)(x- 10)(x - 15) - .443(x - 1)(x- 5)(x- 10)(x 15)(x - 20) - .332(x - 1)(x- 5)(x- 10)(x - 15)(x - 20)(x25)+.04143(x - 1)(x- 5)(x- 10)(x - 15)(x - 20)(x - 25)(x- 30) - .0028(x- 1)(x- 5)(x- 10)(x - 15)(x - 20)(x - 25)(x - 30)(x 35)+.000128354(x - 1)(x- 5)(x- 10)(x - 15)(x - 20)(x- 25)(x30)(x - 35)(x - 40) - .000004172272(x - 1)(x- 5)(x- 10)(x - 15)(x20)(x - 25)(x - 30)(x - 35)(x - 40)(x- 45). We can use this polynomial to predict the Total Coliform reduction of a certain month with x=1 being the first month (Jan 2001).

# Conclusion

• The ideas of constructing a wetland in the Imperial Valley to challenge the contaminants in the New River ended up being more than what was expected with more than 95% average of Total Coliforms eliminated. After this success, there are now more plans to construct more wetlands in other sites after proving their effectiveness in cleaning the country’s most polluted river. There have been various proposed sites such as one in Calexico and also in the Alamo River, thanks to the effort and ingenuity of the Citizen’s Congressional Task Force on the New River.