MILK OF LIME

Sludge liming with milk of lime

Sludge liming with milk of lime inhibits putrefactive processes and significantly reduces pathogenic microorganisms that naturally develop in sewage sludge. Raising the pH to strongly alkaline levels causes denaturation of microbial cell proteins and disrupts their metabolic processes. In practice, this enables effective inactivation of bacteria, viruses and parasite eggs that could pose a sanitary risk. High pH also slows down biological reactions responsible for the decomposition of organic matter, directly reducing the formation of sulphur- and nitrogen-containing compounds responsible for unpleasant odours.

• reduces bacteria and parasites, improving the sanitary safety of the sludge
• limits odour emissions, which is particularly important for the surroundings of wastewater treatment plants
• improves sludge storage properties by stabilising its structure

As a result, limed sludge can be stored for longer periods with a reduced risk of intensive putrefactive processes. It also gains improved handling properties, including lower susceptibility to decomposition and easier forming and handling. This makes further management of the sludge safer and more predictable. In practice, treated sludge may be used, among other applications, for the reclamation of degraded land, improvement of soil properties or in agriculture, provided that all applicable environmental and sanitary requirements are met.

Dosing of milk of lime

Milk of lime is dosed into wastewater or directly into sludge using dosing pumps and appropriately selected mixers. The entire process must be precisely controlled because lime slurry tends to settle and form deposits. Proper system design and the maintenance of stable operating parameters are therefore important.

• appropriate slurry concentration, adjusted to the properties of the sludge
• continuous mixing to prevent sedimentation of lime particles
• real-time pH monitoring to maintain stable process conditions

Incorrect dosing or interruptions in mixing may lead to the accumulation of lime deposits on the walls of pipelines and tanks. For this reason, milk-of-lime dosing systems require regular maintenance and periodic cleaning to maintain their operating efficiency and reduce the risk of failures.