The correct option is (a) 1 only.
Explanation
Grit removal is a crucial stage in the preliminary treatment of wastewater. It is designed to remove heavy inorganic solids such as sand, gravel, eggshells, and metal fragments that could cause damage to pumps and mechanical equipment in subsequent treatment stages.
Statement 1 is correct: In a standard Sewage Treatment Plant (STP) flow, the grit removal tank (or grit chamber) typically follows the bar screens. Bar screens first remove large floating objects (rags, sticks, plastics), and the water then passes into the grit chamber to remove heavy, abrasive inorganic particles before entering primary sedimentation tanks.
Statement 2 is incorrect: The working principle of a grit chamber involves reducing the velocity of the wastewater flow, not increasing it. The speed is controlled to be low enough to allow heavy inorganic particles (grit and sand) to settle out by gravity, but high enough to keep lighter organic solids in suspension so they can be treated in biological processes later. Increasing the speed would prevent sedimentation.
Key Takeaway: Grit chambers operate on the principle of differential sedimentation, utilizing controlled velocity reduction to separate heavy inorganic matter from lighter organic solids.