This paper was written as part of the 2001 Alaska Ocean Sciences Bowl high school competition. The conclusions in this report are solely those of the student authors.
Wastewater Management for Juneau, Alaska: A Plan for the Future
Written in part by each
of the following:
Juneau-Douglas High School
10016 Crazy Horse Dr.
Juneau, Alaska 99801
Table of Contents
Statement of Purpose (2.1)
Definition of Wastewater (2.2)
Treatment Processes (4.2)
Effluent Limitations (4.3)
Management Plan (5)
Ultraviolet Disinfection (5.2)
Overflow Treatment (5.3)
City Sewer (5.5)
Population Growth (5.6)
Web Sites (8)
Index of Tables and Figures
Timeline of Notable Wastewater Events 1999-2000 (Table 1)
Location of the Gastineau Channel (Figure 1)
Wastewater Processing Capacity (Table 2)
Mendenhall Valley Treatment Plant Flow Diagram (Figure 2)
Effluent Limitations for Mendenhall and Juneau-Douglas Facilities (Table 3)
Methods of Disinfection (Table 4)
Juneau Population Growth 1990-2050 (Figure 3)
Timeline of Suggested Improvements (Figure 4)
In response to this we propose that the City make several changes in the next 50 years, including adopting wastewater disinfection by ultraviolet rays; connecting a subdivision discharging high amounts of fecal coliform to the city sewer; separating storm water and wastewater systems to decrease the occurrences of wastewater overflows; partially treating these overflows when they do occur and enlarging Juneauís wastewater processing capacity by increasing the capacity of existing facilities and/or building new ones in applicable areas.
On September 11, 2000 the EPA (Environmental Protection Agency) initiated a $60,000 lawsuit and may currently be bringing criminal charges against the City and Borough of Juneau for continual inadequate sewage treatment and repeated discharges of raw sewage into the Mendenhall River and Gastineau Channel. In 1999, errors in the Mendenhall Wastewater Treatment Facility caused sewage to back-up into homes. EPA studies show that discharges have exceeded the permitted fecal coliform levels by 437,000 percent (Table 1). This report explores and seeks to remedy these issues.
Wastewater is composed of other things than human waste, toilet tissue and water. Untreated wastewater contains solvents, detergents, pesticides, cleaners, inks, grit, tampons, condoms, rags, hair and much more. Undisinfected wastewater also contains high amounts of dangerous microorganisms, including fecal coliform. Because Juneaus wastewater is combined with storm water, it also contains oils, pesticides and other road chemicals .
The Gastineau Channel, a glacial fjord estuary between Douglas Island and the mainland, extends from the south end of Douglas Island to the entrance of Fritz Cove and is approximately 18 miles in length. The width of the channel varies from 0.3 miles to 1.8 miles (DeLorme. Alaska Atlas.1992). The north end of the channel contains the Mendenhall Wetlands State Game Refuge, into which the Mendenhall River flows (Figure 1).
The Mendenhall Wetlands was created by isostatic rebound as Southeast Alaska rises further and further above sea level. It was established as a state wildlife refuge in 1976 and contains 4,000 acres of saltwater wetlands. The convergence of the Gastineu Channel, the Mendenhall River, and Auke Bay into the wetlands creates a very unique and diverse habitat. This habitat is home to many species of plants, birds, fish, and mammals. (Table 2)
The Mendenhall Wastewater Treatment Facility, located on Radcliffe Road, is the primary wastewater treatment facility for the Juneau area, serving a resident population of 20,000. The facility is designed to handle a wastewater flow of 4.9 mgd (million gallons per day). The average flow is 2.5 mgd, but the facility can, in emergencies, handle a flow of 7 to 8 mgd. The Juneau-Douglas Wastewater Treatment Facility, the other main treatment facility in Juneau, is located just south of the city and serves a population of about 15,000. It has an average flow of 2 mgd and has a maximum capacity of 5 mgd. The Auke Bay Wastewater Treatment Facility is the smallest of the three facilities, processing 80,000 gallons of water per day. It has a maximum processing capacity of 140,000 gallons per day (Table 2).
Juneau-Douglas and Mendenhall Facilities (4.2.1)
The Juneau-Douglas and Mendenhall Wastewater Treatment Facilites treat wastewater by using pre-treatment, secondary treatment, disinfection and solids handling (Table 3).
Pretreatment at the Juneau-Douglas facility consists of grit removal and comminution. Grit removal is achieved by directing the influent flow into a settling tank. Heavier materials (grit) in the water sink to the bottom of the tank where they are collected by a radial rotating sweep and discharged into a grinding comminution. From the settling tank, water is directed through a bar stream, a grate perpendicular to the water flow, which traps less dense solids the settling tank has missed. In the Mendenhall facility the influent flows through a bar screen and is pumped into the sequential batch reactor, which removes solids.
Secondary Treatment (22.214.171.124)
Both the Juneau-Douglas facility and the Mendenhall facility lack primary treatment, or the slow settling of solids, usually through a sand bed filter. In the Juneau-Douglas facility water flows from the bar stream into two pipes, each of which is directed to one of two identical aeration basins. This marks the beginning of secondary treatment where microorganisms are cultivated to digest any organic matter in the water. A mixer on each end of the basin provides oxygen for the microorganisms and ensures that they remain in contact with organic matter.
From the aeration basins, water flows to the bottom of a clarifier. The least dense water rises to the top, spilling out of the grated edges. Another rotating sweep, this one on the surface of the water, collects the scum which rises to the surface. From the clarifiers, some water is pumped back into the aeration basin to reuse the decomposing microorganisms. The Mendenhall facility provides secondary treatment in aeration/clarifying basins. The wastewater is pumped from the SBR building to the basins, where it settles for 75 minutes before beginning aeration.
At the Juneau-Douglas facility the water is then disinfected using ultra-violet light, which destroys microorganisms by disrupting their DNA. The water flows through a concrete trench which has perpendicular bars of UV lights four inches apart. Thus, all water passes within two inches of a light. After disinfection the effluent is discharged into Gastineau Channel. At the Mendenhall facility water is decanted from the aeration/clarification basins and pumped to a chlorine contact chamber where it is injected with chlorine. After dechlorination using sulfur dioxide, it is discharged into the Mendenhall River.
Solids Handling (126.96.36.199)
At the Juneau-Douglas facility the grit and scum that have been removed from the water are directed to a digester. The digester is like an aeration basin. It blends its contents with a mixer and allows them to be digested by microorganisms. The digester serves to break down organic solids and to limit the number of microorganisms in the aeration basins. A percentage of microorganisms are diverted to the digester and not back to the aeration basins, keeping the number in the aeration basins manageable. At both plants the solids are mixed with a polymer, which allows them to clump together. This mixture is then pumped to a belt filter press, where it is compressed into a mud-like sludge. The belt press decreases the percentage of water in the sludge from 98.5 to 84 percent. After exiting the belt press, the sludge from the Mendenhall facility is shipped to Juneau-Douglas, where sludge from both facilities is incinerated. Remaining ash is filtered and sent to the digester.
Auke Bay Facility (4.2.2)
The pre-treatment and secondary treatment processes used at the Auke Bay Wastewater Treatment Facility are similar to those used at the other two facilities, consisting of a bar screen, settlement and aeration. The water is chlorinated, but not dechlorinated, before discharge into Auke Bay.
The effluent limitations on publicly run wastewater treatment plants are regulated by technology-based and water quality-based limits. Technology-based limits are based on what is feasible with the technology available. The technology-based limits for each facility cover three areas: five day Biochemical Oxygen Demand (BOD5), Total Suspended Solids (TSS) and Acidity (pH). Water-quality limits are based on the state and federal water quality standards. In addition to the water quality-limits, the state has an antidegradation policy which protects water quality when the water is above the required standard and keeps water which just meets the standard from being degraded below the standard. The water quality-based limits include standards for fecal coliform, copper, lead, silver, zinc, total ammonia and total residual chlorine (Table 3).
To determine permit limitations, the EPA first determines which technology-based limits will be incorporated into the permit. Then the water quality expected based on these limits is evaluated. If any exceedences of water quality standards are possible, the EPA must include water quality-based limits in the permit. The permit limits will reflect whichever of the limits are more stringent. Section 301(b)(1)(B) of the Clean Water Act requires a secondary treatment, which is defined by technology-based limits, of all publicly owned treatment works (POTWs) and section 301(b)(1)(3) requires that pollutants are controlled through the use of ěbest practicable control technology currently availableî (BPT).
To maintain a safe and healthy environment in Juneau, some changes in its wastewater treatment processes should be implemented. First, the Mendenhall Wastewater Treatment Plant must adhere to the regulations of the Clean Water Act. It must remove excess amounts of fecal coliform from its discharge into the Mendenhall River. Two ways to accomplish this are by converting chlorine disinfection processes to those using ultraviolet lights and by partially treating wastewater overflow. Second, concentrated excesses of fecal coliform from other sources must be eliminated. Third, areas not connected to the city sewer must be connected in cases which would be economically viable. Fourth, Juneaus wastewater processing capacity must grow in accordance with its population and the percent of that population which uses the city sewer.
The wavelength of ultraviolet rays is between 200 and 300nm, a range which is germicidal. Ultraviolet light eliminates threats of bacteria, viruses, yeasts and molds by disrupting their DNA. Disinfection by ultraviolet light eliminates fecal coliform more effectively than chlorine disinfection, the method currently used at the Mendenhall Wastewater Treatment Facility. The use of UV rays to eliminate viruses is 100 percent effective, while the use of chlorine is not. Another benefit of disinfection by ultraviolet light is that it does not chemically alter the structure of the water. Disinfection by UV rays also requires no handling of toxic materials or reactions which produce toxic by-products. Chlorine is dangerous and expensive to ship, store and handle. Ultraviolet lights are powered by electricity, which is abundant and inexpensive in Juneau, due to the use of hydro-electric power. UV disinfection is the safest and most cost effective type of treatment on todayís market.Ý In comparison to chlorine, UV disinfection is easy to maintain and requires very little effort. Chlorine disinfection requires personnel training and accidents occur often. UV disinfects instantaneously while chlorine requires a contact time of 20 to 30 minutes. Chlorine disinfection requires a mixing tank while UV disinfection does not. Finally, even when water is dechlorinated, some residual chlorine is discharged into the environment (Table 4).
Disinfection of municipal wastewater by ultraviolet light is rapidly becoming commonplace in modern wastewater treatment facilities. Because new and revised permits often regulate chlorine discharge, municipalities adopt ultraviolet disinfection in place of costly dechlorination systems. The Auke Bay Wastewater Treatment Facility would also benefit from UV disinfection. The facility discharges 80,000 gallons of chlorinated water into Auke Bay each day. In this sensitive marine environment, chlorine bonds to organic molecules and creates carcinogenic compounds. Because of its small size and lack of a dechlorination process, the Auke Bay Wastewater Treatment Facility could switch to ultraviolet disinfection relatively easily (Ernie Muller, pers. com.).
Currently, whenever too much wastewater enters the facility, raw sewage is released through an overflow pipe directly into the Mendenhall River. This could be remedied in two ways. If the Mendenhall facility created a holding tank for emergency overflows, the extra wastewater could be contained and treated later, instead of being discharged into the Mendenhall River. The other option is to partially treat the overflow. If the overflow were disinfected, the amount of fecal coliform and other hazardous materials would be greatly diminished. A bar grate to catch trash, large objects and solids would be easy to install. Overflow disinfection by ultraviolet light would decrease fecal coliform in wastewater overflows, resulting in fewer violations of facility permits or the Clean Water Act. Ultraviolet lights could be installed in the overflow pipe and switched on only when the pipe was in use. Although this process would not rid the water of all fecal coliform, it would significantly decrease the amount present in the overflow effluent. Maintenance, activation and deactivation of an ultraviolet disinfection system for an overflow pipe would be minimal in comparison to a chlorine disinfection system, and an overflow disinfection system is necessary to ensure that fecal coliform limits are met consistently (Figure 4).
The Bonnie Brae subdivision on Douglas Island discharges nearly 30,000 gallons per day of partially treated wastewater with a high fecal coliform count. The wastewater is treated solely with secondary treatment by a private system for each house. It is then discharged through a common pipe into the Gastineau Channel Wildlife Refuge without disinfection. The water standard for the wildlife refuge is the raw-shellfish standard, which means that ingestion of raw shellfish found in the refuge should not be a health hazard. Because of Bonnie Braes limited wastewater processing system, this standard cannot be met. At the point of effluent discharge there is a 1000 ft mixing zone in which this standard is not met. However, because the point of discharge is 8 ft above low tide, some of the wastewater is not mixed, but is left on the beach in front of the houses of North Douglas. This area is marked with hazardous waste signs.
Beginning in the spring of 2001, the City and Borough of Juneau will construct a pipe from the Bonnie Brae subdivision across the Gastineau Channel to the mainland, where it will connect to an existing sewer line leading to the Juneau-Douglas Wastewater Treatment Facility. The added 40,000 gallons per day from Bonnie Brae will have a negligible impact on the facility, which processes an average of 2million gallons per day. This project will take approximately one year to complete (Figure 4).
In 1999 the City of Juneau inspected the private wastewater systems of the Bonnie Brae and Bay View communities. One third of the systems had malfunctioned due to lack of cleaning or maintenance. Ernie Muller (pers. com.), head of the Department of Public works, estimates that a high percentage of private wastewater treatment systems are malfunctioning or simply not working. Because the City does not inspect private wastewater systems outside of the Bonnie Brae and Bay View communities these malfunctions go unrecorded by the City and in many cases unnoticed by the systemsí owners.
The areas of Juneau not on city sewer include rural, sparsely populated areas such as Douglas Island north of the Juneau-Douglas Bridge, the mainland south of the Juneau-Douglas Wastewater Treatment Facility, the Mendenhall Peninsula, and the mainland north of Auke Bay. The City has plans to connect the Bonnie Brae subdivision on Douglas Island, and would like to connect the region between Bonnie Brae and the Juneau-Douglas Bridge. However, the City has noticed a trend which follows the connection of lots to the city sewer: development. Once a lot is connected its property value increases dramatically, so its owners subdivide it, resulting in twice as many people living on the same area of land. If this were to happen in North Douglas, it would aggravate an existing traffic problem on the Douglas end of the Juneau-Douglas Bridge. The Department of Transportation is contemplating the addition of a roundabout to the road system at this point to alleviate the problem, but until this occurs, the City is not likely to connect this area to the city sewer.
It is not likely that the other areas mentioned will be connected in the near future. The Mendenhall Peninsula is mostly solid rock, which would make any drilling or digging needed extremely expensive and time-consuming. Most buildings on the Mendenhall Peninsula are downhill from the closest existing sewer, so the wastewater would have to be pumped uphill from the buildings to the sewer, requiring vast amounts of energy.
The areas north of Auke Bay and south of the Juneau-Douglas Wastewater Treatment Facility are so sparsely populated that the cost of connecting them to the city sewer would be more than the total value of the property in those areas. Connecting one lot under good conditions costs $20,000 to $30,000 (Ernie Muller, pers. com.). Good conditions include lots on flat land and ground made up of soil or clay, not rock. Because many of the lots in these areas are undeveloped, they are valued at less than this amount. However, if the development in these areas increases in the future, it would be appropriate to connect them to the city sewer (Figure 4).
Juneau has an annual 1.3% growth rate and an estimated population of 30,189 (1999 census). In the year 2050, Juneau will contain approximately 58,600 residents (Figure 3). The current sewage treatment plants are built to serve approximately 35,000 residents. The City at this point does not know how it will address concerns regarding population growth in the future. Juneaus sewer system is relatively new: the Juneau-Douglas facility was the first wastewater treatment facility in Juneau; it started operating 25 years ago. The Mendenhall facility was added 12 years ago. Up to this point, population growth has not presented a serious problem to the wastewater management of Juneau. However, in 15 to 20 years, the predicted influent flow (based on population growth and percent of population using city sewer) will exceed the amount the existing wastewater treatment facilities can process.
At this point it will be necessary to expand existing facilities and/or build new ones. Which of these will be needed depends on the geographical distribution of the population growth. Future expansion into areas far away from existing wastewater treatment facilities will make connections to them increasingly expensive and inefficient. One of the areas most likely to be developed in the next fifty years is the western side of Douglas Island. If this should occur, it would be extremely difficult to pump wastewater around the north end of Douglas to one of the existing wastewater facilities. A treatment facility on North Douglas would alleviate the problems of population growth and transportation of wastewater to a treatment facility (Figure 4)
Juneaus wastewater systems are currently funded by the use of sewer bills and budget appropriations. The wastewater treatment facilities are run like businesses. Revenue from the facilities is funneled into a enterprise fund. The retained earnings of this fund are the main source for all repairs needed on sewer lines and on the facilities themselves. If money is needed for an unusually large repair, the Public Works Department asks the Assembly for money from the city budget. For extremely large projects such as the construction of a new wastewater treatment facility, the Public Works Department uses a combination of state grants and loans and federal general obligation bonds.
One means of paying for wastewater treatment improvements is to increase Juneaus flat sewer rate. Another possibility is to change the flat sewer rate to a variable rate. The use of a variable rate would force people to pay more attention to their wastewater, but it also has the potential to put too much weight on the economically disadvantaged.
Connecting areas to the city sewer ($20,000 to $30,000 per lot) and separating storm water and wastewater ($100,000 per 100m of piping) would be paid for by the wastewater enterprise fund and money from the city budget. Landowners pay $5000 per lot for connection to the city sewer.
Substituting ultraviolet rays for chlorine disinfection costs approximately $2 million. The expansion of existing facilities or the creation of new ones would require tens of millions of dollars, depending on the size of the facility and the methods it would use. Projects of this size would receive money from state and federal grants and loans. It is the responsibility of the city, state and federal governments to decide if regulation water quality is worth this much money. Perhaps in the light of possible criminal charges and a $60,000 fine from the EPA, these remedies to the currently malfunctioning wastewater treatment processes will be adopted.
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