Industries all over the spectrum use and dispose of water for a variety of purposes. This includes manufacturing on a wide scale, like in the case of batteries, chemicals, plastics, paper, iron and steel. Power plants, textile mills, oil and gas industries, food industries, and of course water treatment plants all use, reuse, and discard water on massive scales. Water that’s used in these industries comes in contact with numerous pollutants that need to be treated before it can be used again or released into surface water. These can include heavy metals such as cobalt, uranium, arsenic, mercury, floating sediments and solids, human or food waste, other natural or added chemicals like ammonia or sulfuric acid.
Oftentimes, to reduce sewage costs, industries will choose to perform one or more pre-treatment processes on their own wastewater before sending it on to municipal treatment facilities, or they may choose to treat it fully on-site before releasing it to the local ecosystem. Often, in the latter case, they need to either transport or further treat sediments that were removed from the original waste stream.
There are lots of ways that water is treated in order to remove these pollutants. This can include separating oil from water in an oil separator, trapping solids within a sediment or debris trap, or filtering, trapping, or skimming out sludge (or allowing slurry to settle). Other treatment methods include the addition of disinfecting chemicals, clarifiers in the way of settling tanks, and carbon or sand filters. Some industrial waste is too toxic and/or too resistant to disinfectant methods to be returned directly to surface water. In these cases, permanent storage is often necessary, either allowing enough time for these chemicals to break down on their own, or through the process of evapotranspiration over a long period.
Clarifier or Settling Tank
Clarifiers are used to remove solids through a process called sedimentation, where suspended particles are allowed to settle and thicken. Solids are then removed via scraping sludge at the bottom of the tank, or by skimming scum floating at the top. Flocculants and coagulants are added to the water sometimes in order to encourage particles to join together and become large, therefore making them easier to catch and remove.
Other designs involve using the sludge itself, referred to as activated sludge. Activated sludge refers to a process where pre-grown bacteria and microbes from later in the process are injected into earlier stages in the treatment series. This encourages sediment and chemical breakdown in the earlier tanks and helps remove solids and sludge from the secondary reservoirs. Here, any excess biological growth or remaining solids are also removed through a clarifying tank
Baffles are used in every stage of this process, used to separate clarifying vs settling tanks, separate intake and outtake flows, protect pumps from sediment, and to ensure adequate HRT for proper treatment time.
Oil and Gas Booms or Separators
Baffles are used both in oil spill clean-ups and within oil/water separators in order to trap oil floating on top of the water. Booms are short, floating curtains that are typically deployed in larger bodies of water. Baffles in oil/water separators are usually part of a compartment within a watertight vault where separation and sediment trapping take place. Oil trapped on the surface is prevented from escaping further into treatment and is typically skimmed off the top of the water by floating or mechanical skimmers. Oil floats to the top of water because it’s lighter, and heavier solids fall to the bottom. Oil can be skimmed off the top of the water after being trapped by baffles or booms, and wastewater can move further into the treatment system. The barrier is kept in place via ballast chains or anchors if placed where there is natural movement, like a current. In tanks or reservoirs, baffles typically come in the form of static walls in order to redirect water flow as well.
