WHERE DOES THE WASTEWATER WE GENERATE GO?

C. L. Cunningham, Adult Independent Studies, University of South Alabama, Mobile, AL 36688. E-Mail catlee72@yahoo.com.

In the past 100 years the population has shifted from being mostly rural to being greatly urbanized. The environment is also changing partly due to this migration to the cities. Many people do not know or do not remember the differences between storm drains and sanitary sewer drains and this leads to problems that endanger the health and safety of everything living in this environment. This report defines some of the ways we dispose of wastewater and what happens when disposal is done improperly. There are several issues of concern; sanitary sewer overflows are at the top of this list. Addressed in this report are several other causes for the problems that plague the sanitary sewer system.

Introduction

There is a need to educate the general public about what happens to the wastewater they generate each day. Most adults have some vague idea about where this waste goes; however, it is not enough to know that when you wash your clothes the wastewater goes down the drain and ends up at the treatment plant somewhere. Some people do not even understand that storm drains and sewers are not the same thing. This report clarifies these issues and presents to the public information on how wastewater is treated, what happens when substances or objects that are prohibited find their way into the collection system, and how they need to be responsible users of these facilities.

The report presents evidence describing what can happen to these systems when inappropriate things are put into these sewers. Few people know that human skeletons have been found in the collection systems of most municipalities, along with other once living things (Goodman 2002). After interviewing several treatment plant operators, one issue stood out. They said that putting objects such as aerosol cans into the sewer lines can seriously affect the health of the treatment plant personnel. Aerosol cans not only interfere with the filtering processing they can explode and injure the attending personnel. By letting the public know these facts, there may be a detectible decline in the number of such items found at the treatment plant.

Maintaining the collection infrastructure and treatment plant and the treatment of waste from all the residents of a city is a monumental and expensive task. Not only are there costs from the normal maintenance of the lines, there are costs that come from unnecessary repairs. Those fall into categories such as: vandalism, unusual weather, and stoppage due to inappropriate items being placed into the lines. Just because an item will fit in a manhole does not mean that it is acceptable to put that item down the sewer. Another aspect of the cost of maintaining the sewer system is the infiltration of rainwater from resident’s pipes (McGregor 2003). Since the early 1990’s, Mobile has been aggressively searching for such and getting the residents to repair the problems. This has helped lower the amount of infiltration in the system. Of course, no discussion of sewer maintenance problems would be complete without speaking on the serious excessive concentration of FOG (fats, oils and grease) in the collection system. There are two type of FOG. The first is nonpolar FOG which comes from petroleum or mineral origins. This type can be detrimental to the wastewater treatment plant during the biologic phase of the process by inhibiting the microorganisms used to break down the waste. The second type is polar FOG which comes from animal or vegetable origins. This type of FOG is responsible for a large percentage of the sewer overflows (Pitts 2002). As non polar FOG cools it hardens and begins to cling to the pipe walls eventually building up enough to block the flow of the wastewater.

Research Question

Do people know about sewer treatment and the difference between a storm drain and a sanitary sewer? Are Mobile’s sewer rates in line with the norm for sewer rates throughout the United States? Does the maintenance and repair of the sewer system account for the rates? Can the public can help lessen the need for sewer maintenance and, if so, how?

Methods

The first interviews were informal questions asked to random citizens involving what they knew about the storm drain and sewer systems. A mini survey was emailed to members of the American Municipal Sewerage Association (AMSA) requesting up to date information on sewer rates and problems encountered in their collection systems. There was light response, but the information gathered is used as informational points in the report. I interviewed several individuals directly involved with the local collection system in order to get up-to-date information on the most pressing issues of concern in the local sewer collection system. In addition, the report contains information gathered by the research of journals, articles, trade newsletters and government websites.

Results

There are several avenues that can be used to dispose of the wastewater we generate: septic systems, storm drains and sanitary sewers. Septic systems consist of a tank and field lines to distribute the wastewater into the earth for further filtering. Such systems are efficient as long as properly maintained and the level of the water table is periodically monitored in low lying areas to insure that the system can operate properly.

Storm drains (sometimes called storm sewers) are not the same thing as sanitary sewers. These underground channels that were meant to collect storm water runoff. Whatever goes into this drainage system is not treated in any way and eventually ends up in public waters (i.e. rivers, streams, the bay) It is very important that everyone understands that anyone letting used oil, antifreeze, pesticides, herbicides, weeds, grass cuttings and pet feces go down the driveway into the storm drains are adding to the contamination of our local waters. These are the same waters we regard with concern because “someone” is causing the water quality to deteriorate (Fleming, H. & Slack, D. 2001). I asked a couple of elementary aged children if throwing an empty soft drink can on the side of the road could cause water pollution. Both said no, how could it? It is only litter. They were amazed to know that there was even a chance that the can could reach their favorite fishing waters.

Sanitary sewers were built to transport the normal waste generated by humans to a facility where it is treated to make it safe for discharge into public waters. Over the years people have forgotten what it was like to worry about waste treatment. Years ago most people had to treat their waste through a septic system. They knew that they couldn’t put just any old thing down the drain. However, once we became an urban culture, we collectively forgot. For example, according to Goodman (2002), even human remains have been found in most municipal sewer collection systems. This was also verified through interviews with some of the individuals contacted in other locations. They reported that, although such things are not a daily occurrence, they do happen. They also reported a number of animals, toys, aerosol cans, razors, needles, etc.

During my interviews with various municipal sewer officials, it became apparent that there are many problems but maintenance goes to the head of the list. Over the years, water and sewer companies across the nation changed and expanded. As we might assume, the most attention for maintenance was paid to the water distribution area, mainly because the general public immediately notices if there is something not quite right with their water (odd smell, color, taste). This was an advantage because these small problems were fixed and never allowed to develop into major systemic problems. As a result of the focus being on water distribution and not equally shared with sewer collection, many of our nation’s cities are under a consent decree. Consent decrees can be the result of lawsuits between two parties. If the defendant is the local municipal utility and plaintiff is a private or a state entity, consent decrees can be used to enforce agreed upon remedies to the problems listed in the complaint. Those involving sewer overflows generally mandate renovation and maintenance of the sewer collection system, as well as monitoring and enforcing of grease control and several other sections which are individual to each city.

Sewer rates in most places, Mobile included, are generally higher than water rates. The reason for this in Mobile is that it cost significantly more to treat a gallon of wastewater than it does to treat a gallon of drinking water. In addition, the cost of maintaining the collection system and correcting problems must be considered. Table 1 is a list of sewer rates as collected from the mini-survey sent to the AMSA members. Note that the rates are similar in the south east and that Mobile is in line with the average.

Discussion & Conclusions

Generally people do not call the local sewer company and complain that it took 12 seconds to flush the commode when it used to take only 10. Nor do they notice anything about the sound as waste disappears down the dark hole as long as it goes. This is what led the way for our sewers across the nation to become poorly maintained and the problems associated with transportation of sewage to increase exponentially. Sewer overflows are one of the major problems throughout the United States (Civil Engineering 2002). The mandated cost of sewer renovation, restoration, and general maintenance is between $20 million to $3 billion a year depending once again on if the city is under a consent decree, the size of the system and the condition of the city’s system. There are many different types of problems. Some are easily understandable; however, deliberate destruction or inhibition of the pipe is not as easy to fathom. For example, a resident not wishing to pay connection fees and monthly fees made his own connection and if a video camera was not used may have never been found. The point is not only dishonesty, but the fact that intrusion into the main was not done properly allowing seepage from the sewer when the level in the main reached the intruding pipe.

One of the newer methods to repair damaged pipelines is the insertion of a liner into the pipe. In Los Angeles this type of repair began in 1986. It cost them $93 million to line 40 miles of pipe using slip-lining. They also did a project using PVC liner pipe to rehabilitate 3 miles of sewer line at a cost of $6 million. In 1991 they did a project of 1.3 miles for $580,000 (Howard 2001). Mobile is using this method in some of its repair but cost figures on this method of repair were not received by the date of this report. In any event this method, although costly, allows localities to enjoy longer performance of the sewer line then with the replacement method.

The maintenance issue although serious is only one component of sewer problems. The next serious problem is a result of blockages caused by natural growth of roots and what the public puts down the drain (Fig. 1) . If butter or bacon is added to food as it cooks and then the liquid is washed down the drain, FOG is added to the sewer lines. Fats, oils & grease (FOG) is a major contributing factor to sewer overflow. (Figure 1) Around the nation cities are being required to dictate what is going to be put down the drain from the obvious group, restaurants, to the less obvious group, residents. Los Angeles was placed under a consent decree in 1997 dealing with sewer overflows. This meant they would have to deal with the FOG problem. They developed a program based on education and best management practices to accomplish the reduction of FOG in the sewer lines. Food service establishments (FSE’s) were required to obtain a permit. The permit stated that they would be inspected and that they must implement best management practices. If they failed, the installation of a grease interceptor would be required. Also new establishments either building or remodeling at a value of $100,000 or more are required to install an outside grease trap. The city is educating the FSE’s on how to reclaim, recover, dispose of FOG and in this way prevent it from entering the system and causing overflows (Marshutz 2002).

Mobile came under a consent decree in Spring 2002. Although, there are many issues addressed, the focus of this report is on the sewer overflows and here on FOG. For more information, Mobile’s consent decree can be found at http://www.mawss.com. As part of the consent decree a new grease control program is in place. A brief outline of the program is that food service facilities are inspected for proper business practices: grease trap waste disposal manifest, employee training on FOG, check the grease trap to see if it needs cleaning and proper kitchen procedures. Also the facility can be required to install a properly sized grease trap determined by the facility’s information. All over the United States municipalities are dealing with the oil and grease problem in their sewer collection systems (Russell 2002).

The actions of all residents in our community affect the quality of our environment and also the costs involved in cleanup. This report may help change what waste is dumped, where it is dumped, and educate the community on how ordinary wastewater inevitably ends up in the Dog River or the Mobile Bay by causing either a sanitary sewer overflow or by simply going untreated through the storm drain. The more people hear about the problems and what they can do to help fix them, the more we will see a change for the better in our public waters. It is vital that individuals take action to keep trash, chemicals and articles other than storm water out of the storm drains in order to help maintain and improve the health of our public waters.

References Cited

(April, 2002) EPA releases report on combined sewer overflows. Civil Engineering. 72(4). 31.

Goodman, N. R. & Himmelberger, L. K. (Nov, 2002). Identifying skeletal remains found in sewer. Journal of the American Dental Association, 133(11).1508.

Howard, A. et al. (Oct, 2001). Liner Lessons. Civil Engineering. 71(10), 64. Retrieved February 27, 2003, from Academic Search Elite (5380280).

Marshutz, S. (June, 2002). Get the FOGs out. Reeves Journal: Plumbing, Heating, Cooling, 82(6). 6. Retrieved March 25, 2003, from Academic Search Elite (7354768).

McGregor, J. D. (Jan,2003). The Case of Cleaning. Civil Engineering, 73(1). 60. Retrieved February 27, 2003, from Academic Search Elite (8874690).

Pitts, M. (January, 2002). L. A. ordinance designed to unclog sewer system. Reeves Journal: Plumbing, Heating, Cooling. 82(1). 10.

Russell, J. M. (March, 2002). Cutting grease with ongoing monitoring and maintenance. Water Engineering & Management. 149(3). 17. Retrieved March 25, 2003, from Academic Search Elite (6305846).