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WaterOperator.org Blog

Articles in support of small community water and wastewater operators.

Chemical Grouting: A Solution to Infiltration

Chemical Grouting: A Solution to Infiltration

Editor's Note: We want to thank Avanti International for permission to use their photo as Figure 1 in this post.

Infiltration is defined as an excess of unwanted water entering a sanitary wastewater system from groundwater or storm water. More specifically, infiltration occurs when groundwater enters the sanitary sewer through defects in pipes and manholes (Figure 1). This excess water can cause damage to the collection system when sewers are forced to transport more flow than they are designed to handle. Increased effluent also raises wastewater treatment costs because the facility must treat harmless storm water and groundwater with the sewage. This added flow increases wear on equipment, electrical cost, and overall operation and maintenance expenses. In addition, if the capacity of the collection system or treatment plant is exceeded, untreated wastewater may be discharged into the environment.

infiltration source diagram

Figure 1. Potential Sources for Infiltration

As with most utility problems, there are many potential solutions. For infiltration where defects are localized, some of these solutions include mechanical point repair, injection methods, or rerounding. A discussion of the chemical grout injection option is given below. 

The chemicals used for grouting have been available since the early 1960s. They are usually urethane based and when they come in contact with water react to form a polymer material that is a barrier to water flow. The conditions/steps required for grouting are:

  1. A pipe or joint cannot be failing structurally
  2. There must be a path for the grouting solution to flow out into the soil
  3. The area must be free of debris such as roots, grease and other obstacles that may prevent proper application of the grout.
  4. Application of the chemicals at a pressure higher than the water table of inflowing water.
  5. Final testing of the repair (air pressure or visually).

A video providing an overview of this process using remotely operated equipment is given below.

 

Chemical grouting can also be applied manually and can stop the leak almost instantly. A video of manual grouting for a leak in sewer wall is shown below. 


In summary, chemical grouting technology for stopping infiltration is attractive because the chemicals are non-toxic to the wastewater treatment plant and can be applied using remote controlled equipment or manually for small localized defects. Chemical grouting is a flexible low cost option for infiltration repairing of sewer mains in addition to sewer laterals.

Featured Video: Sewer Dye Testing

Featured Video: Sewer Dye Testing

A municipal sanitary sewer system is designed to collect and transport wastewater from homes, offices, businesses, restaurants and other sources to a municipal wastewater treatment plant for treatment and safe discharge into the environment. If other sources of water are allowed to enter the sewer system, the collection system and wastewater treatment plant can become over loaded allowing untreated water to be discharged. This is defined as sanitary sewer overflows, or SSO’s. One of the biggest sources of excess water is infiltration of storm water and groundwater into the sanitary sewers. A method to detect this infiltration is through dye testing.

Dye testing is a simple procedure where storm drains, yard drains, and the outside of the foundation walls of the house, or other areas are flooded with water to simulate a period of heavy rainfall. The colored water is pumped through the ground and storm water system and appears in the sanitary sewer collection system where leaks occur. This test is simple and complements smoke testing that may have been done previously.

The dye testing procedure can be accomplished in the following steps.

  1. Isolating a section of the storm water network to test by plugging pipes at specific locations. 
  2. Then, bright-dyed water is pumped into the storm water network until it reaches capacity. 
  3. Remote CCTV cameras are deployed into the sanitary sewer system, where any points of storm water ingress are highlighted clearly by the dyed water.

Once the testing is completed, the locations of these sources of infiltration makes the process of repairing these leaks far more straightforward facilitating effective piping and system repairs which keep infiltration to a minimum.

A video showing how dye testing can be carried out is shown below:

Featured Video: Sewer Cleaning in Los Angeles California with Kent Carlson

Featured Video: Sewer Cleaning in Los Angeles California with Kent Carlson

For roughly 30 years Kent Carlson worked for the City of Los Angeles to bring innovation and new technology to the Department of Public Works’ Bureau of Sanitation. When the Bureau observed that new technology was falling behind on their collections side, Kent was brought over to assist with tool development and the standardization of sewer cleaning procedures. Under the mission to reduce sewer overflows and recognize increasing drought in southern California, one of his favorite inventions featured a sewer nozzle designed to reduce water use and save time during cleaning.

In his article with CWEA Water News he offers his predictions on the future of the sewer profession asserting, “I think it’s an exciting future – technology is exploding in this sector – CCTV, GIS, computers on the trucks. Sewer workers of the future will be much better with technology. Rather than using rudimentary brute force for cleaning we’ll get smarter, more strategic and more efficient at what we do.”

Kent’s enthusiasm for tool development is demonstrated in this week’s featured video. The 5-minute video highlights the history of sewer cleaning in Los Angeles as well as a demonstration of how his team tests and develops their sewer cleaning tools. Back in the day, sewer cleaning featured manual removal of clogged pipes and sewer mains. Today, his team takes advantage of high-pressure tools and robotics. Kent says the best tools for sewer cleaning are designed or personally modified by the facility staff. These tools ultimately help the Bureau of Sanitation affordably maintain approximately 6,500 miles of pipe, some of which was originally installed as far back as 1883. We hope this week's featured video inspires your system to find new and innovative ways to help your utility operate more efficiently.

Managing Sanitary Sewer Overflows (SSOs)

Managing Sanitary Sewer Overflows (SSOs)

The U.S. EPA estimates that approximately 23,000 to 75,000 sanitary sewer overflows (SSOs) occur in the United States each year. An SSO is defined by the release of untreated sewage into the environment through an overflow, spill, basement backup, or unpermitted discharge before completed treatment at the sewage plant. These overflows can degrade water quality, cause property damage, and pose serious threats to public and environmental health due to the release of harmful pollutants, disease causing microorganisms, metals, and nutrients into the environment. 

Section 301 of the Clean Water Act prohibits the discharge of pollutants to any Water of the United States from a point source without a National Pollutant Discharge Elimination System (NPDES) permit. To address compliance challenges associated with SSOs, the EPA recently completed a National Compliance Initiative that first began in 2000 to reduce the discharge of raw sewage in national water ways.

SSOs occur through debris or grease blockages, root intrusion, vandalism, inflow and infiltration, improper design, aging infrastructure, operational mistakes, and structural, mechanical, or electrical failures. Typically, the most frequent culprit takes the form of blockages. After an overflow, clean up and response is not only expensive, but traumatic for the impacted communities.

In Queens, NY a sewage backup on the Thanksgiving holiday weekend of 2019 flooded the basements of approximately 100 homeowners creating a putrid odor and exposing the community to harmful pathogens. Liability for residential damages and repairs to the pipe was projected to reach millions of dollars.  The culprit for the backup? While operators initially theorized a grease induced fatberg was to blame, investigation later revealed a collapsed sewer pipe instigated the SSO.

In New England and around the country, many communities maintain collection systems of 100 years old or more. Aging infrastructure exacerbates SSO prevention challenges. As years of wear on system equipment increases, the likelihood of mechanical or electrical failures as well as the opportunity for inflow and infiltration increases. Pipe deterioration due to natural freeze-thaw cycles, environmental conditions, water flow, and water chemistry can also increase the likelihood of structural failures. When this deterioration is not routinely inspected and maintained, resulting failures will only add further hydraulic stress to the system.

The frequency of SSOs can be reduced significantly through preventative maintenance and the implementation of an appropriate asset management program. To upgrade your preventative maintenance program, an article from the March 2017 Kansas Lifeline discusses the basics of lift station maintenance. The Georgia Association of Water Professionals provides a more comprehensive guide of collection system maintenance practices in its 2016 guide Wastewater Collection System Best Management Practices.

Developing an asset management program will allow systems to plan for the replacement or rehabilitation of aging pipes, pumps stations, valves, manholes, and collection system infrastructure. During program development systems can predict and plan for population changes, capacity objectives, equipment deterioration, and more. To encourage proper asset management of collection systems, the EPA developed the CMOM program. CMOM stands for Capacity, Management, Operations, and Maintenance.  The information-based management approach encourages dynamic collection system management through the prioritization of activities and investments. Utilities can access how well their current practices meet the CMOM framework using this Self Assessment Checklist and the EPA Evaluation Guide for CMOM at Sanitary Sewer Collection Systems. Follow up this evaluation by integrating CMOM best practices into a new or updated asset management program using this blog post.

Even with the implementation of these programs, systems should still prepare for the event of an unexpected overflow. As in Queens, NY, preventative maintenance and asset management did not stop the SSO on the Thanksgiving weekend. Systems must be prepared to respond swiftly with a Sanitary Sewer Overflow Response Plan. These emergency response plans will limit potential damages and reduce community distress. By combining preventative maintenance, asset management, and emergency response planning, systems can ensure that their community and its environment have the best protection from SSOs.

Featured Video: What is Water Hammer?

Featured Video: What is Water Hammer?

Any water or wastewater operator should possess a strong understanding of water hammer and the implications it can have on piping systems. Water hammer, also referred to as hydraulic shock, occurs when there is a sudden change in flow velocity or direction that results in a momentary increase in pressure. If high enough, the pressure can cause damage to pipes, fittings, and valves. An example where water hammer can occur is when an operator rapidly closes a valve halting flow and sending a shockwave through the system. In Jefferson City, MO, operators responding to a ruptured water main created a second break during repairs as a result of water hammer. Pressure surges can also occur through unexpected power outages or equipment failures.

Engineers consider several variables when designing piping systems to limit potential for water hammer. Whenever a major change is made to the distribution or collection system, implications for water hammer should be evaluated.

This week’s featured video demonstrates how water hammer occurs and what it looks like using 100 feet of clear PVC pipe with an analog and digital pressure gauge. The host explains how engineers can modify the potential for water hammer in piping systems by manipulating the variables that make up the mathematic equation for the pressure profile of a water hammer pulse. Such design parameters include pipe size, recommended operating procures for closing valves, and more. Watch the video to understand how the design considerations for your piping system impact water hammer.

Featured Video: Flushable Wipe's Effects on Our Sewer System

Featured Video: Flushable Wipe's Effects on Our Sewer System

Many collection systems struggle to prevent the costly and time consuming repairs associated with flushable wipes. Despite the label these wipes remain intact in sewer systems. They often clump into large blockages held together by grease. When the blockage becomes too large, sewers experience sanitary backups and pricey pump damage. 

This week’s featured video reviews the management options for flushable wipes as explained by Great Lakes Water Authority. One common solution for wipe buildup requires the installation of sewer grates and filter screens. Though operators will be required to regularly clear away wipe accumulation, systems can plan for the added maintenance expenses while preventing unexpected downtime. Other systems may choose to break down wipes with chopper pumps or grinder pumps, however this can lead to reweaving later in the collection system.

The video ultimately demonstrates that there is no single and efficient method to avoid wipe backups other than consumer education. With the final costs of wipe maintenance funded by the rate-payer, collection systems should be vocal in educating their customers about the products that can and cannot be flushed down the toilet. For more information on flushable products, check out our blog post Will it Flush.

Spooky Sewers and Things That Go Bump at the Treatment Plant: 2018 Edition

Spooky Sewers and Things That Go Bump at the Treatment Plant: 2018 Edition
An October chill is in the air and darkness is falling earlier and earlier. It must be time to share our annual bone-chilling list of some of the wierdest, wackiest and downright most frightening water operator stories we came across this year (check out last year's list here)!
 

First, can you imagine what it would be like to get sucked through a sewer for over a mile? Well, it happened to this man when his safety harness came undone back in 2010. And although he survives, the crappy experience is surely something he will never forget. 

While we are talking collections O&M, here's a video describing one characteristic of a successful wastewater operator: a strong stomach. Another characteristic? Knowing not to "fling this on your partner."  And believe me, you don't want to know what "this" is!

Sometimes, though, what flows into a sewer simply doesn't come out, no matter how much you work on it. That is when you call in the professionals: sewer divers.

This is exactly what the water system in Charleston, SC did when they could not clear an obstruction earlier this month. They sent specialized sewer divers 80-90 feet deep into raw sewage in complete darkness to search for the obstruction with their hands..

What did they find? You guessed it: a large mass of "flushable" wipes. Lucky for us, the water system documented the whole episode on social media, but respectfully shot the pictures in low-res for our benefit.

If you want to dive deeper into the topic of sewer exploration, we double dare you to watch this video about a man who swims through Mexico City's wastewater system on a regular basis to keep it working. 

Other types of obstructions have to be dealt with in other ways. This past summer, utility workers spotted an alligator swimming in the Mineral Springs, PA wastewater treatment plant. A private contractor hired by the state Fish and Boat Commission had to use dead animals as bait to try and snag the gator with a fishing hook. 

You have to admit, wastewater often gets a bad wrap. To prove this, just ask any operator from Baltimore's wastewater treatment plant what happened there back in 2009. That was the year they had to call in experts to deal with a 4-acre spider web that had coated the plant. According to a scientific paper that appeared in American Entomologist, the “silk lay piled on the floor in rope-like clumps as thick as a fire hose” where plant employees had swept aside the webbing to access equipment. Scientists estimate the megaweb contained about 107 million spiders

Finally, it wouldn't be Halloween without ghosts, or ghost water, to be more precise. What is ghost water you ask? Well, pervasive leaks and long repair delays are causing water to disappear in Kansas City, Missouri (a kind of haunting experienced by water systems all across the country it seems). According to this 2017 article, nobody knows exactly where the water is going, but the water department points to faulty meters, theft, aging pipes and abandoned houses. Spooky!


Featured Video: The Science Behind Exploding Manhole Covers

Featured Video: The Science Behind Exploding Manhole Covers

Every season has its challenges for public works departments, and now that spring is just around the corner, it is pretty obvious that this past winter came with more than its fair share. Yet we are not in the clear quite yet, as this news story about two manhole explosions just a few weeks ago demonstrates. In fact, as winter winds down, accumulated road salt compounds corrode through underground electrical cables, causing sparks to ignite gases that can build up in confined spaces. With over 2,000 annual incidents in New York City alone, exploding manholes are not a joke: they can be dangerous, destructive and downright difficult to predict.

And while large cities like New York City are especially prone to these incidents due to aging infrastructure and the sheer amount of underground electrical cables present, small towns are definitely not immune. For example, in 2014 the tiny town of Sauget, Illinois (pop. 150) experienced an explosion so powerful manhold covers damaged overhead power lines.  

 Find out more about how road salt compounds contribute to this problem in this week's featured video.  

While explosions are the most dramatic hazard associated with manholes, research suggests that manholes are in general one of the most dangerous work locations for water system staff. In fact, according to AFSCME, fully one-third of all injuries/deaths of workers occur in or around manholes. Check out this safety presentation hosted by Michigan WEA for more information on the types of hazards presented by manholes and how to protect yourself from them. 

And if you have any lingering doubts about the force, and destructive power, of an expoding manhole, take a look at this video

Featured Video: An Inflow and Infiltration Reduction Program in Missouri

Featured Video: An Inflow and Infiltration Reduction Program in Missouri

Inflow and infiltration (I/I) can be very costly for small communities, especially those communities with outdated combined wastewater/stormwater systems or collection systems in poor repair. According to this classic National Small Flows Clearinghouse article, I/I problems place additional burdens on these older and/or fragile systems because the extra water that seeps or flows into them can be very damaging, and, in some cases, even cause contamination issues.

This week's featured video describes how the City of Columbia, Missouri is attempting to locate, identify, and correct improper connections and defects that cause these inflow and infiltration problems so that their system capacity improves, and sanitary sewer overflows and basement backups are eliminated.