By Barry Orr and Fatih Karadagli
Wastewater operators in Canada believe new flushability specifications will help reduce the cost and inconvenience to customers from blocked sewer pipes and the impacts to the environment from the flushing of inappropriate products down the toilet. Currently we should only be flushing the 3Ps (Pee, Poo and Toilet Paper) down our toilets.
The growth in the number of products labelled “flushable”, including wipes has been a multi-million-dollar headache for water and wastewater utilities. In Canada, it is evident that wipes cause or contribute to pipe blockages and pump clogs. Removal of such materials from wastewater systems is costing Canadians over $250 million per year according to the Municipal Enforcement Sewer Use Group (MESUG).
The wipe industry are represented by the Association of the Nonwoven Fabrics Industry (INDA) and the European Disposables and Nonwovens Association (EDANA). INDA & EDANA developed guidelines and test methods to assess a wipe for its flushability.
Their Guidance Document (no. 4) serves as a platform to evaluate wipes; however, pass/fail criteria of each test method potentially suits the interests of wipe manufacturers as we discuss further below, while it fails to protect wastewater infrastructure, municipal funds, public health, and consumers’ interests.
What are “flushable” wipes?
Wipes are manufactured as nonwoven sheets of natural and manmade fibers such as cellulose, cotton, regenerated cellulose (rayon, lyocell), polyester, and high-density polyethylene (HDPE). They are marketed as either flushable, or non-flushable.
The fibres are mixed at various ratios through hydroentanglement, in which high speed jets of water strike a web of fibres so that the fibers knot around one another, or by a meltblown process during which polymer is heated to a high temperature then extruded through small nozzels while hot air is being blown.
The resulting product is a substrate that usually has a high wet-strength, because synthetic fibers retain their form, shape, and strength in a moist state. This high wet strength is a desired outcome for wipe manufactures, so the product will not fall apart during its life-cycle.
A recent study looked at the physical and mechanical characteristics of non-flushable wipes, flushable wipes, and toilet papers and found that flushable wipes are more similar to non-flushable wipes than they are to toilet paper.
Flushable wipes are heavier, denser, thicker and have larger surface areas than toilet papers. The researchers found that under wet conditions, flushable wipes maintain most of their strength, as they are composed of synthetic fibers that retain their shape and strength.
For instance, toilet papers lose on average 90% of their strength when wet, allowing it to disperse in toilets, plumbing systems, and sewers. In contrast, flushable wipes only lose an average of 29% of their strength in wet conditions, meaning it takes much more force to breakdown a wipe.
Effects of flushable wipes on wastewater infrastructure and the environment
Readers of ES&E magazine will already be familiar with the impact of flushable wipes on wastewater pumps, pipes and other infrastructure. Indeed wastewater utilities from around the world have been reporting that wipes are responsible for most pipe blockages and pump clogs in sewer networks. However, a growing concern is flushable wipes’ contribution to microplastic pollution, which threatens ecosystems and even human health.
Microplastics/microfibres are a source of contamination as they are carriers of chemical pollution (plasticizers and additives) also known as Persistent Organic Pollutants (POP) that are adsorbed onto their surfaces.
These chemically polluted microplastics are then ingested by all types of organisms such as crustaceans, fish, birds, and ultimately, by humans via the food chain.
Microplastics increase the risk of cancer or disruptions to other systems like the endocrine system, leading to problems with sexual development and reproduction in animals and humans.
What is being done
Consumers assume that “flushable” products must have been tested rigorously for their compatibility with household plumbing and sewer systems, when in fact there is no standard definition of what is flushable, and no standard method to assess flushability.
Several organizations such as INDA/EDANA and the International Water Services Flushability Group (IWSFG) have developed test methods and technical specifications to define flushable products. As an example, IWSFG and INDA/EDANA both proposed a Slosh Box Disintegration Test (SBDT) to evaluate disintegration of a wipe in water.
A slosh box is a framed-glass-box that rocks from one side to the other through a cam and lever mechanism. The purpose of this test is to assess the disintegration performance of a wipe material when it is subjected to hydraulic forces typically found in continuous flow conditions in small diameter (8 inch/200 mm) sewer pipes, i.e., turbulent forces equivalent to a Reynolds number of 20,000.
Table 1 compares experimental conditions and pass/fail criteria of the Slosh-box test procedure as proposed by IWSFG and by INDA/EDANA. The critical differences appear in turbulence conditions (18 vs. 26 rpm), test durations (0.5 vs 1 h), and pass/fail criteria (95% vs. 60%). Such differences indicate that INDA/EDANA’s procedure is relatively tolerant, i.e., 60% of a wipe should disintegrate after 1 hour of shaking at 26 rotations per minute (rpm). In contrast, IWSFG offers more stringent criteria, i.e., 95% disintegration after 30 minutes of shaking at 18 rpm.
|Experimental Parameter||Requirement by IWSFG||Requirement by INDA/EDANA|
|Sample||A single sheet||A single sheet|
|Water volume (L)||4||2|
|Mixing speed of Slosh-box (rotations per minute)||18||26|
|Mixing time (hours)||0.5||1|
|Expected ratio of disintegration to pass (% of initial dry mass)||95% < 25 mm||60% < 12.5 mm|
In parallel, INDA/EDANA’s test procedures are applicable only to wipes, while IWSFG’s test protocols cover any product that will be labeled as “flushable”, e.g., wipes, colostomy bags, and toilet- bowl cleaning brushes.
Flushable wipes are not like toilet paper. Their size, strength and material composition prevent them from breaking down in wastewater systems, and even if they break down, they contribute to microplastic pollution in the environment.
INDA/EDANA’s guidelines serves to protect interests of wipe manufacturers, but it fails to protect wastewater infrastructure, municipal funds, public health, and consumers’ interests.
Government regulations are needed urgently to define technical characteristics of flushable products. In this direction, IWSFG’s technical specifications and test methods clearly differentiate the products that are truly “flushable” from those that are not.
In light of these arguments and recent research findings, Fisheries and Oceans Canada have received a report from MESUG, stating the key reasons for why INDA/EDANA’s flushability guidelines are unacceptable by the Canadian wastewater professionals.
Barry Orr is the spokesperson for Municipal Enforcement Sewer Use Group (MESUG), City of London, Ontario, Canada. Email: email@example.com
Fatih Karadagli is an associate professor of environmental engineering at Sakarya University, Turkey. Email: firstname.lastname@example.org