![]() ![]() ![]() Thioguard’s specific chemical and physical properties add alkalinity to the water system, moderately modify pH, stimulate biological activity and improve solids quality. This inefficiency prompts many operators to increase MLSS, MCRTs/SRTs, and oxygen addition, which in turn leads to increased energy and solids disposal costs. Moreover, unless pH is carefully monitored at both bioreactor influent and effluent, pH spikes and instability in the aeration basins and BNRs leads to inefficient biological processes. This alkalinity depletion often goes unnoticed because it is masked by pH elevation, which is often assumed to be linked proportionately to alkalinity. Through unintended lime softening, alkalinity levels can be depleted going into secondary treatment. Why? Lime softening often gets in the way of alkalinity supplementation. When evaluated in its entirety, it is rare that lime is the most cost-effective choice for pH modification and alkalinity supplementation. On the surface, the cheap cost of lime is an appealing choice. With growing needs for alkalinity in nitrification and BNR processes, operators are often faced with the challenge of supplying higher levels (in excess of 30 mg/L) of alkalinity without upsetting processes or depleting the chemical budget. It is often difficult to balance the competing reactions of lime softening and alkalinity supplementation with the use of lime in wastewater. In severe cases, it leads to line blockages and SSOs. Hydrated lime added to collections systems increases O&M costs related to formation of scale and accumulated solids/sludge. To see more, go to click Downloads, and view “Thioguard Takes the Cake and Makes it Better” and “Thioguard Bridges the Cation Gap – Saves Biosolids $$.” In fact, customers using Thioguard have reported reductions of 15 to 25 percent in total solids/sludge produced, due to a combination of improved biological performance and reduced inorganic solids loading. In contrast, Thioguard reactions in wastewater produce only water and water-soluble products as TDS with no added sludge. On a chemical basis, one ton of lime can generate as much as 11.5 to 15.5 tons of 20 percent sludge cake to remove or dispose. ![]() The use of lime generates significant amounts of sludge in wastewater collections and treatment. At the elevated pHs for caustic soda and lime, solids and scale begin to form and cause problems. Reactor systems treated with an equivalent amount of Thioguard, caustic soda and lime. Equivalent amounts of acid added to each over time. Reactor systems treated to an initial pH of 8.5 using Thioguard, caustic soda and lime. And, because of these differences in properties, the impacts they impart and the utility for their use are starkly different. The simple fact: Thioguard, lime slurry and caustic soda all have different physical and chemical properties that affect how each responds to, and reacts with, the systems to which they are added. Thioguard’s customers have stated that they are being told lime slurry is similar to Thioguard (municipal-grade magnesium hydroxide), and can be used as an alternative in the many applications in which Thioguard is used. The addition of lime may increase the volume of waste sludge up to 50 percent.Lime typically generates more sludge than other coagulants.By itself, large quantities of lime are required for effectiveness.Lime is an effective phosphate removal agent, but results in a large sludge volume.Lime produces calcium carbonate in wastewater, which acts as a coagulant for hardness and particulate matter.The EPA Wastewater Technology Fact Sheet: Chemical Precipitation EPA 832-F-00-018 states: Get Instrumentation articles, news and videos right in your inbox! Sign up now.īecause of the high solubility of both caustic soda and lime, pH often becomes biologically prohibitive before ideal alkalinity levels and process stability can be reached.Īdded without proper feed controls, the use of lime in, or prior to, primary treatment can actually reduce alkalinity going into the secondary treatment processes by precipitating CaCO 3 in the primary clarifiers. ![]()
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