Water Treatment: Introduction

Suzette R. Burckhard, PhD, PECivil and Environmental

EngineeringSouth Dakota State UniversityEngineering the Future 2014

Objectives

• Facts– Define MCL, MCLG, MRDL, MRDLG, Treatment

Technique• Application

– Explain the basic treatment operations necessary to treat surface water and ground water to drinking water standards

Water Quality review• Physical Characteristics

– color, turbidity, temperature, taste, odor

• Chemical Characteristics– chemical components, concentrations, pH

• Microbiological– Coliforms, Legionella, Giardia lamblia,

Cryptosporidium

• Radiological– radiation level (Curies)

Water Quality Standards

• Maximum Contaminant Levels (MCLs), MCL Goal

• Secondary MCLs• Treatment

Technology (TT)• Maximum Residual

Disinfectant Level (MRDL), MRDL Goal

Water classification

• Ground water– Constant composition– High mineral content– Low turbidity– Low or no color– May be bacteriologically safe– No dissolved oxygen– High hardness

– H2S, Fe, Mn

– Possible chemical toxicity

Water Classification

• Surface Water– Varying composition– Low mineral content– High turbidity– Color– Microorganisms present– Dissolved oxygen– Low hardness– Tastes and odors– Possible Chemical toxicity

Treatment• Limited treatment plants

– Filtering is minimum required treatment• Coagulation plants

– Surface water treatment• Softening plants

– Groundwater treatment• Typical treatment steps

– Acquire water to be treated (surface water and/or groundwater)– Add chemical to soften or coagulate SS (depends on source)– Mix water and chemical to allow full reaction– Settle out particles– Filter (polish) water– Disinfect – Distribute

Limited treatment plants

• High quality water sources

• Address a specific water quality issue– Disinfection– Corrosion control– Fluoridation– Iron/manganese removal– Softening

Coagulation plants• Treat surface water• Remove

– Color, turbidity, taste and odors, bacteria • Typical treatment steps

– Screening– Rapid mixing– Flocculation– Sedimentation– Filtration– Disinfection then distribution

Softening plants• Typically treat groundwater

– Similar types of operations as coagulation but with different chemicals– Main purpose of treatment is to remove hardness

• Typical treatment steps– Chemical addition – rapid mixing– Reaction– Settling– Recarbonization– Filtering– Disinfection and distribution

Comparison of Softening and Coagulation Plant Operations