Elements of the system
27 The ACCC adduced evidence that the basic design of Australian and international sewers is the same. In particular, Australian sewerage systems are relevantly similar to United States and English sewerage systems. Thus, for example, Mr Drinkwater treated his English experience as relevant to the Australian experience. To the extent that it was appropriate for KCA to rely on the INDA/EDANA GD3 Guidelines at all, there is no good reason to doubt that it was appropriate to rely on them in marketing products as flushable in Australia.
28 The following explanation of the system is based on KCA's written submissions, which were not disputed in this regard.
29 When a toilet is flushed, items in the toilet that are not too large, too heavy or too voluminous to pass through the toilet are flushed into a household or commercial drainline. The flushing action releases a volume of water from the head tank, which forces the water and material in the toilet bowl to begin to circulate and flow down and through the toilet's submerged trap.
30 Within the drainline, wastewater from shower and bath drains, kitchen and laundry sinks, wash basins, and dishwashers and washing machine drains, joins the flow of material flushed from the toilet and travels through the drainline, which may include turns, junctions with other drain pipes and vertical drops.
31 In urban environments, the drainline joins the municipal sewer pipes at a connection point near the edge of a private property.
32 Wastewater flows are primarily comprised of water, but also include a wide variety of organic and inorganic waste materials and substances. Apart from wastewater and the "Three Ps" (pee, poo and (toilet) paper), waste materials and substances found in the wastewater system include food scraps, fats, oils, grease (from kitchen sinks and dishwashers), hair, sand, grit, dirt and soaps (from showers, baths and wash basins), lint (from washing machines), paper towels, facial tissues, plastic, wipes (of various types), feminine hygiene products and contraceptives and, particularly during wet weather, groundwater and stormwater flows that enter the system.
33 Wastewater systems in Australia are predominantly gravity-fed, that is, the pipes are laid at a gradient sufficient for the pipes to be "self-cleansing", which means there is sufficient energy within the flow of water in the pipe to carry solids from a customer's property into the main sewer and onto the treatment plant. This generally provides enough turbulence to prevent solids from settling out of the wastewater flow. The flow of wastewater through the pipes is disturbed by drops, twists and turns. As the pipes flow downhill, the diameter of the pipes generally increases as the pipe is joined by other pipes and carries wastewater flows from other properties and other sewer pipes.
34 Often, sewer pipes pass through one or more pumping stations on the way to a treatment plant where the level of the pipes reaches an inefficient depth and needs to be pumped up to a higher level so as to resume the gravity-fed flow. The larger municipal sewer pipes will then typically converge at a final "headworks pumping station" at the entrance to the treatment plant.
35 Some pumping stations include screens (which catch and remove material from the flow) or grinders (which cut material into smaller pieces and pass it downstream) located near where wastewater first enters the wet well in the pumping station and before the wastewater reaches the pump itself. Wet wells within a pump may include features designed to deal with solids in the wastewater, including the turbulence of water flowing into the wet well that can break up a solid mass that has formed in the wet well, corner fillets (to prevent dead spots), sloping floors, mixers (to keep solids in suspension), and grit traps. Wet wells are periodically cleaned out, either manually or through an automated process, to remove settled solids at the bottom of the wet well and floating materials at the top. Wastewater passing through a pump station is pumped through by an "impeller", a rapidly rotating (720-1,800 rpm) propeller like component that is specifically designed and rated by manufacturers to successfully pump solids-bearing liquids of at least a specified minimum size.
36 Multiple considerations affect the design for a pumping station. For example, Colin Hester, Manager, Commercial Water and Trade Waste of Queensland Urban Utilities (QUU), a statutory body that supplies drinking water, recycled water and wastewater services to South East Queensland, stated:
16. Many of QUU's pumping stations have had their screens removed, due to the risk of overflow when a screen becomes covered in debris including wipes, and also due to the maintenance burden imposed by the requirement to regularly clean the wipes off the screens by manual processes. The risk of pumps fouling or rocks striking and damaging the impellers has been identified by QUU in many of these instances as being a lesser operational risk than repeated overflows of sewerage. For example, about 4 years ago, when I held the role of Manager Source Control and Environmental Compliance … I was involved in reporting environmental overflows at pump stations sometimes caused by blockages on screens. In some instances, the preventative action taken was to remove the screens.
17. [S]creens are "intended to prevent solid materials in the wastewater from potentially becoming clogged within pumps, valves, or piping located downstream". From QUU's perspective, the only purpose of having screens installed at the pumping station is to protect QUU's infrastructure … This is consistent with the intent being to protect the equipment and to maintain the flow, rather than to perform some type of treatment function of separating solids from the wastewater for collection (as in the case with the function of screens fitting at treatment plant).
37 Most wastewater treatment plants have screens (inclined vertical bars or round openings) located near where wastewater first enters the treatment plant. This is intended to protect the plant's downstream equipment, including pumps, valves and piping. The screens catch larger solid material (including faecal matter and toilet paper) and remove it from the flow, with the collected material taken to landfill. Typically, the screens at the treatment plant clean themselves automatically. There is then a grit removal process at the treatment plant involving inorganic materials, such as grit and sand, settling (via gravity, aeration or a vortex motion within a tank) and being pumped out of the tank and disposed to landfill, whilst the organic material flows on to other treatment processes. Primary settling tanks then allow solids to settle into a sludge at the bottom of the tank (where the sludge moves on to biological treatment and disinfection), whilst a mechanical moving skimmer removes floating materials (such as grease, scum and small plastics) off the top of the wastewater in the tank.
38 In the case of QUU, Mr Hester said:
22. Screening systems are always included at QUU's wastewater treatment plants. These are finer screens than those installed at the relevant QUU pumping stations, being 3-6mm screens. At the wastewater treatment plant, the screens are the first stage of the treatment process, as well as being there to perform the function of protecting the equipment within the plant.
23. In respect of the pumping stations the imperative is to protect the assets and keep the network moving, whereas, at treatment plants, the objective is to protect the assets and to separate the wastewater from the solids contained within it. It is for these reasons that the screens are finer than those that might be installed at a pumping station … so that more debris is filtered out of the wastewater.
24. These screens at the treatment plant are also automatically raked, as opposed to the manual process applied at those QUU pumping stations that have screens installed. However, sometimes human intervention is required, for example, when wipes, rags or other debris, including feminine or other personal hygiene products, accumulate and cannot be dislodged by means of the automated process.
39 Bernie Sheridan, Manager, Treatment at Sydney Water Corporation, a statutory body that supplies drinking water and wastewater services to greater metropolitan Sydney, expressed the view, which I accept, that if a wipe takes longer than 30 minutes to break down in the system, it is possible that it might arrive intact at the plant and it is also possible that such a wipe can bypass the screens at the entry point to the treatment plant.