Thiruvananthapuram: Kerala Water Authority (KWA) has proposed increasing its hydrated lime requirement for the Aruvikkara division by 18.6%, from 580 tonnes in 2025–26 to 688.10 tonnes in 2026–27. The decision was taken amid rising silt levels and turbidity in raw water drawn from Aruvikkara dam.A KWA source at the executive engineer’s office in Aruvikkara said turbidity levels, which were around 60 nephelometric turbidity units (NTU) last year, had risen to between 80 and 100 NTU this year because of increased silt in the raw water.“The silt content in the water has increased, resulting in higher turbidity levels. This means we need to use more chemicals during treatment to remove suspended impurities. Alum helps remove these particles, but its use can affect the pH balance of the water. Hydrated lime is therefore added to regulate the pH and maintain the chemical balance required for effective treatment,” the source said.Silt consists of fine particles of soil and other mineral matter suspended in water. Alum helps these particles clump together so they can settle or be removed during subsequent treatment stages.The proposed procurement specifies hydrated lime with a calcium hydroxide content of at least 86%. The final decision on the proposed procurement is expected on Nov 2, according to KWA sources.Meanwhile, cleaning of the Aruvikkara treatment plant has not taken place for the past three months, the source said. The earlier tender process, held in April, could not be completed because the bidder did not meet the prescribed eligibility criteria. KWA has since initiated a fresh tender for the cleaning work.
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