There is a lot of overlap between the various goals of storing, containing, and treating wastewater. Yet the structures used for these various stages differ greatly in design and the need for durability. Trying to repurpose a pond or tank designed for primary storage into a secondary containment measure may work well or backfire, depending on the overlap in design features and requirements. Understanding how these three methods vary, and overlap, will help you determine how they should work together in a large scale project that needs more than a single storage point.
Containment vs Storage
Storage can also be referred to as primary containment for wastewater. Any structure designed to hold the water without leaking or loss, regardless of short- or long-term plans, is a storage unit. Wastewater containment in most industries generally refers to secondary containment and not the primary form. This level of protection is designed to capture any wastewater that leaks, overtops, or seeps out of the primary containment system. So, a storage tank sitting over a pad, covered in geomembrane, with appropriately high edges, is a system that combines both storage and containment. A double-walled tank also provides both functions at once. However, not all forms of storage or containment offer the same level of protection. In general, separately constructed containment holds more liquid and provides more reliable performance than combined methods like double wall designs.
Storage vs Treatment
Storage and treatment tanks and ponds are often confused for each other, especially in projects that require long-term storage. However, treatment ponds and tanks are actively or passively improving the wastewater in some way. This may be due to the use of aerations or pumps to circulate the waste, the addition of chemicals and additives to settle out particles and kill bacteria, or a combination of different treatments spread out over the course of many months. Storage tanks are simply designed to hold wastewater with no particular goal of changing its composition or safety level. Some waste products don’t respond to basic treatments and must be removed to a hazardous waste facility or dump. Storage ponds and tanks make more sense than treatment structures in those cases. Almost all facilities designing some kind of treatment system will also need storage to hold incoming wastewater until there’s space for it in the treatment ponds. Secondary containment is also necessary for treatment ponds and tanks, not just storage units.
Combing Functions in One System
As mentioned before, double wall tanks aren’t the ideal way to combine storage, treatment, and containment functions into one unit. First, these tanks are even heavier and more expensive to transport and install than single walled units. Second, most regulations require a secondary containment system for hazardous wastewater that is capable of holding 100% of the primary storage volume. That’s a lot of extra space to add to an already large and heavy tank. Even if you must build above ground, to satisfy local or federal regulations, custom manufactured tanks and ponds make it easier to combine all three functions into the same system. Double layer liner systems create both primary and secondary containment in the same footprint while preventing leaks. If you do use a tank, consider installing a basin complete with a geomembrane liner below it to act as its secondary containment barrier.
In addition to liners and other materials used below the wastewater to contain it, many systems also benefit from removable or permanent covers over the top. Storage containers, in particular, benefit from covers to control the release of unwanted or potentially dangerous gas and fumes. These covers must be vented to remove the gas that builds up under their surfaces. Covers can also serve as protection methods to keep humans and animals from accidentally falling into the wastewater. However, these security covers need frames to support them or they pose a hazard when someone falls in and becomes trapped in the stretched material.
Looking for the materials to build storage, containment, and treatment ponds and tanks? Turn to BTL Liners for everything you need. Our ArmorPro geomembrane liner is perfect for challenging wastewater management projects, and we also fabricate ArmorCover that is ideal for topping off tanks and ponds.