Chapter 27, Problem 8R

Summary Introduction

To match:

The stage of treatment with the processes used in wastewater treatment.

Introduction:

In sewage treatment, the first step involves the separation of large floating solids present in the wastewater. The resultant sewage, effluent is then passed through sedimentation tanks to remove more solid waste materials. Sewage solids settling at the bottom are called as sludge. After primary sewage treatment, the dissolved organic compounds present in the sewage contributes to high biochemical oxygen demand (BOD) levels. Secondary sewage treatment is mostly biological and involved in the significant reduction of BOD by removing most of the organic compounds. Strong aeration boosts the growth of aerobic bacteria and other microorganisms that oxidize the dissolved organic compounds. The organic matter gets converted to water and carbon dioxide. Tertiary sewage treatment is mostly physical and chemical treatment and depends less on the biological treatment. It is involved in the removal of nitrogen, phosphorus and residual BOD present in the effluent from secondary treatment.