Challenge details:

The manufacturing industry uses potassium hydroxide (KOH) in the process along with other chemicals. Post usage in the process, the KOH solution loses its effectiveness and is replaced with a fresh solution. The exhausted KOH solution with some impurities, known as concentric alkali effluent, is then sent to an effluent treatment system for water recovery and ensuring zero liquid discharge (ZLD).

The feed to the effluent treatment system are concentric alkali effluent (i.e. exhausted KOH solution) and concentric acid effluent. This feed is currently treated through chemical pretreatment followed by UF -RO. The RO reject from the treatment system is then further passed through thermal ZLD system for further recovery of water.

The challenge lies in recovery of KOH from concentrated alkali effluent before it is mixed with concentric acid effluent in pretreatment section of effluent treatment scheme.

The quality of recovered KOH shall be such that it can be reused in the main manufacturing process again.

The flow rate of concentric alkali effluent ranges between 10 to 14 m³/hr. This effluent has total dissolved solids (~50000 to 60000 ppm), potassium (~20000 to 24000 ppm), chloride (4000 to 6000 ppm), sulphate as SO4 (900 to 1200 ppm) and silica (~9000 to 10000 ppm), with low suspended solids.

The recovered KOH must meet the specified quality standards to enable its reuse in manufacturing process. Quality of fresh KOH procured for the process has KOH concentration of 45-48%, clear and colourless EL-grade quality, and strict impurity limits (e.g., chloride ≤3 ppm, sulphate as SO4 ≤3 ppm). The sourced KOH of above quality is then diluted with water to 3-5% during its use in the manufacturing. It is preferred if the recovered KOH is of concentration near to 45% to avoid any major changes in the chemical transfer and dilution system.

The KOH recovery system shall not have any major negative impact on existing effluent treatment setup and shall integrate without disrupting the system.

Additionally, the proposed solution must account for energy efficiency and shall be commercially viable in terms of life cycle costing.

We are looking for a cost-effective and sustainable KOH recovery process that aligns with its reusability in current operations and shall be adopted within existing infrastructure.