Broad Infrastructure Program Includes Capture System for CSO Floatables

Dec. 28, 2000

About the author: Frank Sudol is chief of research and program development in the Department of Engineering, Newark, New Jersey. His article is based upon a presentation he made in April of this year at the Coalition to Restore Urban Waters - Friends of Trashed River II Conference, held in New York.

For cities to survive, while protecting environmentally-sensitive lands such as wetlands and aquifer recharge areas, it is essential that suburban sprawl be curtailed. The costs, in economic terms, in lost time, in excess energy consumption, and in depletion of natural resources, are well documented. If sustainable development is to be accomplished in urban areas, priority should be placed on revitalizing existing urban infrastructure. Rather than extend costly new infrastructure into environmentally-sensitive areas, we should utilize the investment already made in the infrastructure in our cities. This is especially true with respect to protecting and conserving water resources.

Recent business expansion in Newark, New Jersey, reflects the positive pro-business, pro-environment position taken by the city. Newark is the third oldest city in the United States, and yet the recipient of many recent local, state and national environmental awards. Why should businesses that promote and improve the environment locate in your city? In Newark, incentives are offered to companies such as recycling manufacturers which utilize secondary materials collected by the city to produce new commodities. We also provide adequate infrastructure, which curtails the cost and environmental damage resulting from suburban sprawl.

Why is this important? Because new and expanded businesses create new employment opportunities and expand economic activity. While being environmentally conscious, Newark has been responsible for bringing in thousands of jobs and millions of dollars in annual business at over 70 recycling enterprises. Additionally, the city is creating new employment opportunities to clean up the environment, including waterways, as will be described later. Further, it is helping the state maintain a leadership position in environmental cleanup and job creation efforts. For example, Newark recycles more than half of its solid waste in a program said to be one of the largest, and according to the USEPA, one of the best in the nation.

Similarly, it has developed a very effective water cleanup program, with several exciting initiatives started in the city to enhance waterways. Communities throughout the United States can benefit from similar measures to entice urban infrastructure revitalization.

Approximately 300 combined sewer overflow points (CSOs) exist in New York City, with another 600 or so in the State of New Jersey. These have to be properly controlled to reduce the quantity of debris entering the waterways of the region. One of the most objectionable CSO discharges is known as floatables-aesthetically displeasing and unsanitary litter commonly washed into combined and storm sewers. Upon discharge, it fouls waterways and the shores of the ocean, lakes and rivers. Floatables cause significant water pollution problems which must be controlled according to federal and state requirements.

Federal Water PollutionControl Mandate

Floatable materials in water endanger marine biota through entanglement and ingestion, and form waterborne slicks which cause navigational hazards and washup on shorelines. In 1988, there were 34 beach day closures due to washups of floatables on New Jersey and Long Island beaches. This was at least three times the number of beach days lost in other years. During the beach debris washups of 1987 and 1988, the media focus on medical wastes discouraged many tourists while beach attendance and boating/fishing activities declined. Economic losses were estimated at a billion dollars.

Combined sewer overflows are one of the most serious water pollution problems we face. On April 11, 1994, the USEPA finalized a CSO policy. The action ended the debate among federal policy-makers and local officials representing communities confronting record compliance costs on how to control overflows and improve water quality. The final policy established a comprehensive approach for directing compliance efforts by the nearly 1,100 communities in the United States that were developed at a time when engineering practices combined sanitary and stormwater flows into one collection system-a combined sewer system. Concentrated in the Northeast and Midwest, these sewer systems overflow an average of 50 to 80 times per year, according to the EPA.

The final policy has one more hurdle to clear in the enactment of the CSO policy in the form of an amendment to the Clean Water Act, before communities can count on this as the definitive framework for setting future clean water permit requirements. The Clinton Administration, in January, 1994, recommended adoption of the CSO policy as one of numerous amendments to the Clean Water Act. The Senate Environment and Public Works Committee incorporated this recommendation, which in effect will codify the policy, in its version of the Clean Water Act renewal-S. 1114. House Public Works, and Transportation Committee Chairman Mineta included a similar provision in his proposed Clean Water Act renewal-H.R. 3948.

Under the EPA policy, municipalities with combined sewers would be required to improve street and catch basin maintenance programs, make maximum use of collection systems for storage of waste, improve pretreatment requirements, eliminate overflows during dry weather and keep the public informed of overflow occurrences and impacts.

Long-term plans have to give highest priority to environmentally sensitive waterways and include input from the public. In addition, the financial capability of municipalities can be taken into account in devising long-term plans.

The effort to develop a final policy began in 1989, when EPA issued a draft CSO strategy, a document subsequently modified through public comments and an intensive process of negotiation among interested parties, including federal, state and local officials and the public. Motivating the process was the consensus that strict adherence to the Clean Water Act would impose unthinkable compliance costs on CSO communities. EPA has estimated that compliance, with current law, would require CSO communities to expend approximately $160 billion over the next 10 years beyond the substantial investments already made by many communities. Under the final policy, assuming enactment by Congress, the estimated compliance costs will fall to $41 billion.

The policy requires municipalities, including Newark and New York City, to develop short- and long-term plans for remediating CSOs, which occur during rain storms when water in storm sewers and raw sewage combine to overflow into nearby waterways. CSOs account for most floatables and bacterial contamination at the New Jersey Shore.

The new policy requires municipalities to work with the USEPA and the states to develop long-term plans to control combined sewer overflows at a level that will meet water quality standards. In addition, municipalities are required to take a number of immediate steps including limiting floatables, maximizing the flow of sewage to treatment facilities and monitoring to determine the effect of controls.

CSOs can occur during any summer thunderstorm or rain of less than a half inch. As the water inundates the combined storm and sanitary collection system, the flow that would normally go to a treatment plant is diverted either through a weir overflow or an electro-mechanically operated regulator chamber at the plant into a waterway. This is done to prevent flooding at the treatment plant. In the case of New York, which has 6,000 miles of combined sewer lines, the result can be a massive deluge of untreated sewage and debris.

Newark's Plan: A Model

With respect to water quality improvements, Newark has made significant advances, for example, in how the city deals with wastewater/stormwater collection and wastewater treatment.

Water Quality-Reduction at Source

  • As a first line of defense to prevent litter and solid waste from being flushed into local waterways, Newark sweeps every street in the City at least weekly using modern equipment, and cleans stormwater catch basins regularly.
  • When a street is resurfaced in Newark, the staff replaces the old catch basin curb inlets, which have a large arched opening along the curb, with gratings that have smaller openings and no curb inlets (Fig. 1). The conversion virtually eliminates the possibility of plastic ware, bottles, cans and other litter from entering the system. The end result is that less debris finds its way into the Passaic River and Newark Bay.
  • The city maintains a recycling depot to which residents may bring used motor oil, which is a common threat to wastewater collection systems.

Water Quality-Removal In the System

  • The City is preparing an engineering study to look into combining under-utilized CSO outfalls. This will divert several overflows to one outfall control device, and will result in fewer CSO remediation structures.
  • Newark is a major partner in the Passaic Valley Sewage Commission (PVSC), the third largest sewerage authority in the country, which recently upgraded its wastewater treatment process from primary to secondary at a cost of over $800 million.

Water Quality-Removal from Waterways and Shores

A novel approach is being utilized in Newark and a city in New York State. Modular capture systems for floatables have been installed at two locations in Newark. The USEPA provided a $400,000 grant for this project through the Clean Water Act Innovative Technology Demonstration program. In the project over 15,000 lb of floatables were captured at these outfall structures during ten storm events. Removal efficiencies of well over 90 percent were achieved in preventing this undesirable debris from reaching the Passaic River and Newark Bay. The project included design, fabrication, and installation of two patent-applied-for TrashTrap netting systems. Supplied by Fresh Creek Technologies, both began operating this spring and their performance is being tracked with a floatables capture monitoring program.

These TrashTrap systems were in-stalled in the waterways in front of and attached to the outfalls. Each incorporates a floating pontoon structure which uses funnels to retain debris in large, mesh nylon bags (Fig. 2). At one site a four-bag system was constructed, while a two-bag set-up was installed at the other location.

During an overflow event, the floatables empty into the receiving water body from the outfall, the wastewater stream's energy and the system's containment boom guiding the litter into the trash bags. After the overflow event, the filled bags are raised, drained and transported to an approved waste site. Replacement mesh bags are put in place in readiness for the next discharge from the outfall.

Over 10 tons (drained weight) of floatables have been captured in just three months from these sites. Records show that approximately two pounds of floatables are captured for every inch of rain falling on a drainage area of one acre. One of these outfalls is a six-ft diameter oval structure, and flow velocities of over five feet per second have been experienced there. The other has exhibited stream velocities of only one or two fps. Debris capture efficiencies at both sites vary between 95 and 98 percent.

A study by HydroQual Incorporated, for the City of New York, indicated that over 68 percent of all captured debris is plastic-26 percent polystyrene and 42 percent other plastics (Fig. 3). Less than one percent is sanitary waste, and only 0.2 percent is attributed to medical waste. Further study of the collected floatables found that 95 percent is 1.3 cm or greater in size.

A modular pre-fabricated TrashTrap system can be installed in two to four weeks. Net replacement takes one to two hours. The nets are supported by floating pontoons which are held in place by steel cables and/or struts connected to the face of the outfall. The assembly, including the nets, floats to compensate for tidal variations and may rest on the bottom during low tide. Heavy curtains hanging from the front of the pontoon structure direct the outfall's discharge through the nets. Bags typically hold 25 cubic feet of floatables which will have a drained weight of up to 500 pounds. Bag removal can be accomplished by lifting them with a boom truck crane and loading them into a carting container. Alternatively, a net removal system using a track-mounted hoist and dumpster may be built into the system.

Reinvigorating the Central City

Recent experience in Newark suggests that to ensure the sustainability of the city, three strategies should be pursued.

First, the city's life support systems (air, water, and soil) must be protected. In practice, this requires the decontamination of air, water and soil by assuring the virtual elimination of discharges of toxic substances, especially those which bioaccumulate and biomagnify in organisms. Pollutants must be reduced to levels that do not impair ecosystem functions through overloading.

Second, the social, cultural, economic and biotic diversity of the city must be protected and enhanced by laws and regulations designed to further this strategy.

Third, resource management strategies must maintain or enhance the efficiency of the man-made infrastructure as well as the integrity of the ecosystem.

Application of these three strategies and implementation of initiatives such as those identified earlier will make possible the reinvigoration of the central city, improve the city's physical and social environment, and enhance the residents' quality of life.

About the Author

Frank Sudol

Sponsored Recommendations

Get Utility Project Solutions

June 13, 2024
Lightweight, durable fiberglass conduit provides engineering benefits, performance and drives savings for successful utility project outcomes.

Meeting the Demands of Wastewater Treatment Plants

May 24, 2024
KAESER understands the important requirements wastewater treatment plant designers and operators consider when evaluating and selecting blowers and compressed air equipment. In...

Modernize OT Cybersecurity to Mitigate Risk

April 25, 2024
Rockwell Automation supports industry-leading Consumer Packaged Goods company, Church & Dwight, along their industrial cybersecurity journey.

2024 Manufacturing Trends Unpacking AI, Workforce, and Cybersecurity

April 25, 2024
The world of manufacturing is changing, and Generative AI is one of the many change agents. The 2024 State of Smart Manufacturing Report takes a deep dive into how Generative ...