2.1 Treatment Objectives

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Do curso por École Polytechnique Fédérale de Lausanne

Introduction to Faecal Sludge Management

209 classificações

École Polytechnique Fédérale de Lausanne

Introduction to Faecal Sludge Management

209 classificações

Do you want learn how to apply concepts of sustainable faecal sludge management (FSM) on a city-wide scale? This course starts with an overview of what faecal sludge is and an introduces you to the engineering fundamentals and required information for the design and selection of technologies. Sanitation solutions are prone to failure if an integrated planning approach that includes stakeholder involvement and the development of appropriate institutional, management and financial arrangements is not implemented. The course therefore dedicates a complete week to presenting the full picture, in addition to technology, that needs to be considered for sustainable solutions. It concludes with a focus on current research and innovations in technologies, to provide an understanding of the most up-to-date options. This course is one of four in the series “Sanitation, Water and Solid Waste for Development".

Na lição

Overview of fundamentals for design and selection of treatment technologies

The second week of this course is based on an integrated engineering design approach, and will introduce fundamentals and required information for the design and selection of technologies, including objectives, mechanisms, quantification and characterization. It also includes the collection and transport of faecal sludge to treatment.

2.1 Treatment Objectives7:34

2.2 Overview of Treatment Mechanisms8:21

2.3 Resource recovery8:13

2.4 Market-driven approach to select treatment products9:18

2.5 Characterization7:22

2.6 Quantification8:42

2.7 Collection and transport technologies7:58

2.8 Wrap-up5:40

Conheça os instrutores

Dr. Linda Strande
Group leader
Management of Excreta, Wastewater and Sludge (MEWS), Eawag-Sandec

This is an F diagram. It is called that

because there 6 important "F" words covered in the diagram.

They are feces, fingers, flies, fields, food and fluids.

Do you know what these 6 F words have to do with treatment objectives?

You'll learn about that in this module.

Following this module you'll be able to name

different treatment objectives, relate health and environmental

impacts to these treatment objectives

and understand that there are different levels of appropriate treatment

depending on end-use of treatment products.

The F diagram depicts fecal oral routes of contamination

which is what we need to prevent to ensure public health.

Fluids, if excreta contaminates drinking water,

fields, if excreta contaminates food crops,

flies, as flies are vector. They are attracted to both

feces and food resulting in cross contamination

and fingers; not adequately washing your hands

before touching food or eating.

Our number 1 goal in Sanitary Engineering

and Fecal Sludge Management is always the protection of public health.

Protection of environmental health is also very important

and as shown in the F diagram, these first 2 goals are

often very closely linked together.

If excreta is contaminating the urban environment,

then it is a public health risk.

A third goal that is important to meet whenever possible

is resource recovery from treatment products

which is also tied closely to the first 2 objectives.

Resource recovery is covered in more detail in other modules.

If it's not possible, then safe disposal is a requirement

to ensure the first 2 goals.

To achieve these goals during treatment processes

we focus on 4 main treatment objectives:

The first one is de-watering.

Fecal sludge is typically over 90% water

so de-watering to seperate the liquid and solids

is very important. De-watering is the removal

of more easily separated water

like wringing out this dripping wet towel

whereas drying is the further removal of water that is bound

with the solids; like then hanging the towel on a laundry line.

De-watering is important because water is heavy

and expensive to transport. Prior to effluent discharge

into the environment, solids and liquids need to be seperated

to ensure adequate treatment can take place

for public and environmental health

and de-watering is typically required for resource recovery.

Also important is stabilization.

Stabilization is the process of readily degradable

organic matter being converted as a result of biodegradation

to more stable complex molecules.

Here we see that happening in composting

with heat being released during the active decomposition phase.

This is important for treatment as readily degradable organic matter

consumes significant amounts of oxygen during degradation.

For example, the classic Streeter-Phelps equation

illustrates what happens if waste water is discharged to a river

with high concentrations of BOD

resulting in the dissolved oxygen in the river being consumed

which can gradually be recovered with time or distance travelled

in the river until readily degradable organic matter

has been consumed and there was no longer an oxygen demand.

Why do we care about oxygen demand?

Because aquatic organisms need dissolved oxygen to live.

Stabilization also results in nutrient stabilization

and odor reduction.

Also important is nutrient management.

Fecal sludge contains nutrients which can be beneficial

if harnessed for resource recovery

but if not managed properly, result in environmental contamination.

Environmental impacts from nutrients include eutrophication

and algal blooms in surface waters and contamination of drinking water.

In pathogen reduction, to revisit what we learned from the F diagram

fecal sludge contains large amounts of micro-organisms

mainly resulting from feces.

These micro-organisms can be pathogenic

and exposure to untreated fecal sludge constitutes

a significant health risk to humans either through

direct contact or indirect exposure.

The transmission cycle of pathogens can be interrupted

by putting barriers in place to block transmission pathways

and prevent cycle completion.

The appropriate level of treatment will depend on the resource recovery

or disposal option. For example,

drying fecal sludge to use it as a fuel in combustion,

our number 1 objective is to de-water to increase fuel potential

and in this case pathogen reduction is not so important

as the sludge will be incinerated.

Whereas on the other hand if treatment products

are to be used as soil conditioners in agriculture

then pathogen reduction is an extremely important

treatment objective.

The first barrier for beneficial use is provided

by the level of pathogen reduction

achieved through the treatment of fecal sludge.

A selection of further post-treatment barriers may include

restriction of use on crops that are eaten raw,

withholding periods between application and harvest

to allow pathogen die off, drip or sub-surface

irrigation methods, restricting worker and public access

during application and use of personal protective equipment

and safe food preparation methods such as thorough cooking,

washing or peeling.

When considering risk of infection, all potential exposure groups

should be accounted for which can be broadly categorized

as workers and their families, surrounding communities

and product consumers.

For more information on a multi-barrier risk based approach

to ensure adequate protection of public health

I recommend the WHO guidelines for safe use of waste-water,

excreta and grey-water in agriculture and aquaculture.

The Sanitation Safety Planning Manual

and the Sanitation Safety Planning Module

in Sandec's Mooc on sanitation systems.

Monitoring to ensure treatment objectives have been met

is an important part of ongoing operations and maintenance.

In summary, in this module you learned about

treatment objectives of de-watering,

stabilization, nutrient managment

and pathogen reduction. Why they are all important

for the protection of human and environmental health

and that appropriate levels of treatment will depend

on the intended end-use.

Thanks for joining. See you next time.

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