Table of Contents

1.0 Introduction

1.1 Water Quality Analysis

1.2 Additional Treatment Required

2.0 Overview of Water Treatment Unit Processes

2.1 Intake and screening

2.2 Coagulation (rapid mix)

2.3 Flocculation

2.4 Clarification / Sedimentation

2.5 Filtration

2.6 Disinfection

3.0 Water Treatment Plant (WTP) Design

3.1 WTP lay-out and flow capacity

3.2 Intake Screen Design

3.3 Coagulation Design

3.3.1 Dosage

3.3.2 Sizing

3.4 Flocculator Design

3.4.1 Size and Rational Speed requirement

3.4.2 Diffuser Wall Type I between flocculators

3.4.3 Diffuser Wall Type II to Sedimentation Basin

3.5 Sedimentation / Clarification Design

3.6 Granular Filtration Design

3.7 Chlorination Disinfection

3.8 Sludge Drying Lagoons

4.0 Environmental Impacts

5.0 Alternate Treatment Processes

6.0 References

1.0 Introduction

While the main role for treating drinking water is to make it safe, it’s also important to treat water for aesthetic purposes. No one wants to drink discolored, odorous water no matter how safe it is.

People like water to taste clear, look clear and smell clear; and it’s the quality of the water source that will determine what kind of treatment it will need.  For instance, mountain spring water fresh from ice will need very little treatment when compared to river water that contains high sediments or groundwater that can be salty or brackish. 

Generally, the water treatment design and planning process is driven by factors such as, water source availability and quality, sustainability assessments of treatment and source options that weigh financial, social and environmental parameters, legal regulatory requirements and the availability of land, skillsets and technology (Crittenden, 2012).  In a conventional water treatment plant (WTP), raw water undergoes a series of processes which include the units below.  In addition, Australian drinking water is treated with fluoride and the pH is adjusted.

• Intake and screening
• Coagulation (rapid mix)
• Flocculation
• Clarification/sedimentation
• Filtration
• Chlorination/disinfection
• Residual management

1.1  Water Quality Analysis

Table 1 is a comparison of the existing raw water quality of the river of interest compared to the Australian Drinking Water Guidelines (ADWG) recommendations.  If ADWG recommendations were not listed for a parameter, then recommendations from the U.S Environmental Protection Agency (EPA) or other government agencies were used.  Both Health-based and Aesthetic-based requirements are outlined.

From the table, river water quality meets recommendations for parameters like the minerals magnesium, lead and calcium.  However, minerals such as sodium and iron exceed the aesthetic limit.

A significant health concern from the river is the insecticide Dieldrin content which is too high; the recommended level here is 0.0003mg/L and the Dieldrin river level is between 0.0005-0.01 mg/L.  That is up to 33 times more than the recommended limit.  Total dissolved solids (TDS) parameter is also at the maximum health limit of 600 mg/L.   The ADWG does not list any particular limit on Total Organic Carbon (TOC), however the U.S EPA recommends less than 2mg/L of TOC for water to be safe to drink.  This indicates the TOC levels in the river can be too high as TOC fluctuates between 2 to 15mg/L.

Table 1. River Water Quality Analysis.  Dieldrin previously used as insecticides and in combination with Aldrin shouldn’t exceed 0.0003mg/L (ADWG p.372)