Chapter 6:

Wastewater Reclamation

and Reuse Winter 2011

Faculty of Engineering & Applied Science

ENGI 9605 – Advanced Wastewater Treatment

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6.1 Introduction

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Water use has more than tripled globally since 1950, and one

out of every six persons does not have regular access to safe

drinking water lack of access to a safe water supply and

sanitation affects the health of 1.2 billion people annually

(UNEP., Water and Wastewater Reuse , 2008)

Water availability in 2000 (measured in terms of 1000m3 per capita/year)

Wastewater reuse plays a key role in facilitating

freshwater protection and integrated water resource

development and management

The major reuse of processed wastewater is for

agricultural irrigation amounting to about 60% of the

total

The second largest reuse is for industrial cooling and

process waters accounting for approximately 30%

The remainder of water reuse is for urban landscape

irrigation and groundwater recharge through surface

percolation less than 10% of the total

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6.2 Wastewater reuse applications

(Viessman et al., Water Supply and Pollution Control, 2009 )

55(Viessman et al., Water Supply and Pollution Control, 2009 )

66

(Viessman et al., Water Supply and Pollution Control, 2009 )

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1. Wastewater reuse for agriculture

Worldwide, agriculture is the largest user of water agriculture receives 67% of total water withdrawal and accounts for 86% of consumption in 2000 in Africa and Asia, an estimated 85 to 90% of all the freshwater use is for agriculture

More efficient use of agricultural water through wastewater reuse is essential for sustainable water management its benefits include

conservation and more rational allocation of freshwater resources particularly in areas under water stress

avoidance of surface water pollution and reduced requirements for artificial fertilizers

soil conservation through humus build-up and prevention of land erosion

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Potential concerns

If wastewater streams come from industrial sources and urban run-off toxic chemicals, salts, or heavy metals in the wastewater may change soil properties, interfere with crop growth, and cause bioaccumulation of toxic materials in food crops

Nutrients in reclaimed water that are important to agriculture include nitrogen, potassium, zinc, boron and sulphur excess nitrogen may cause overgrowth, delayed maturity, and poor quality of crops (e.g., boron is an essential element for plant growth, but excess boron becomes toxic)

Wastewater intended for reuse should be treated adequately and monitored to ensure that it is suitable for the projected applications

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2. Wastewater reuse for industry

Industrial water use accounts for approximately 20% of global freshwater withdrawals

Power generation constitutes a large share of this water usage, with up to 70% of total industrial water used for hydropower, nuclear, and thermal power generation, and 30 to 40% used for other, non-power generation processes

Industrial water reuse has the potential for significant applications, as industrial water demand is expected to increase by 1.5 times by 2025 its benefits include

potential reduction in production costs

heat recovery

potential reduction in costs associated with wastewater treatment and discharge

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Types and examples of industrial water reuse

Potential concerns

(UNEP., Water and Wastewater Reuse , 2008)

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3. Urban applications

A large percentage of water used for urban activities does not need quality as high as that of drinking water dual distribution systems (one for drinking water and the other for reclaimed water) have been utilized widely in various countries this system makes treated wastewater usable

Secondarily treated domestic wastewater followed by sand filtration and disinfection is used for non-potable purposes such as toilet flushing, car washing, garden watering, park planting, and firefighting its benefits include

high volume of wastewater generation and applications for water reuse may benefit from the economy of scale

reduction in the wastewater volume to be treated by municipal wastewater treatment plants

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Scheme of area recycling system in Shinjuku, Tokyo, Japan

(UNEP., Water and Wastewater Reuse , 2008)

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Potential concerns

one of the key concerns for wastewater reuse in urban applications is the protection of public health as urban reuse has the potential to expose a large number of people to disease-causing microorganisms care should be taken to avoid contamination of drinking water by misconnection (cross connection) between potable water pipes and reclaimed water pipes, and also to disinfect reclaimed wastewater properly

corrosion of pipe

blockage of pipe and strainer

biofilm (slime) formation in reservoir tank due to reduction of residual chlorine in reclaimed water

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6.3 Wastewater reclamation technologies

Technology selection process

(Currier et al., Novel Wastewater Reclamation Technology Meets Environmental and Business Challenges, 2008)

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Case study-1

Flow diagram at the Fred Hervey water reclamation plant, EI Paso, TX

(Viessman et al., Water Supply and Pollution Control, 2009 )

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(Viessman et al., Water Supply and Pollution Control, 2009 )

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Case study-2

Process schematic for groundwater replenishment system with a capacity of 100 mgd at Orange County, CA

(Viessman et al., Water Supply and Pollution Control, 2009 )

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(Viessman et al., Water Supply and Pollution Control, 2009 )