3.11 Black Water Transport Systems

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From the course by École Polytechnique Fédérale de Lausanne

Planning & Design of Sanitation Systems and Technologies

438 ratings

École Polytechnique Fédérale de Lausanne

Planning & Design of Sanitation Systems and Technologies

438 ratings

Do you want to learn how to plan affordable and context-specific sanitation solutions? Be up-to-date on the newest developments in urban sanitation planning and programming? Get to know best practice examples of urban sanitation systems in low- and middle-income countries? If yes, this course is for you! This course provides you with an introduction to integrated sanitation planning, both on a citywide scale and for specific contexts such as informal settlements. You will become familiar with different sanitation planning frameworks as well as different systems and technologies relevant along the sanitation value chain. You will learn why systems’ thinking is crucial for urban environmental sanitation, and how to apply key terminology and important concepts. INSTRUCTION Eawag-Sandec and EPFL jointly offer this course with support from sanitation experts of the World Bank and WHO. LANGUAGES We simultaneously offer this course in English and French. The name of the French course is « Planification & Design des Systèmes et Technologies d’Assainissement ». MOOC SERIES This course is one of four in the series “Sanitation, Water and Solid Waste for Development".

From the lesson

Sanitation systems & technologies

During week 3, you will dive more deeply into the technical aspects of different sanitation systems, from the simple single pit system to more complex centralised treatment systems. We introduce you to the main treatment processes in detail, highlighting advantages and disadvantages of each.

3.1 [Semi] Centralized Treatment - Treatment stages6:08

3.2 [Semi] Centralized Treatment - Anaerobic Technologies11:39

3.3 [Semi] Centralized Treatment - Aerobic Technologies12:08

3.4 [Semi] Centralized Treatment - Technologies for Sludge Treatment9:44

3.5 Use and/or Disposal - Agricultural Use as Fertilizer and Soil Conditioner7:00

3.6 Use and/or Disposal - Effluent and other Products8:18

3.7 Emerging Sanitation Technologies2:57

3.8 Introduction to Sanitation Systems11:02

3.9 Waterless Pit-based Systems5:37

3.10 Decentralized Water-based Systems5:09

3.11 Black Water Transport Systems4:42

3.12 Summary Week 31:47

Meet the Instructors

Christoph Lüthi
Dr.
Sanitation, Water and Solid Waste for Development / Eawag

Welcome back to this final section on sanitation systems.

The next few templates that we'll discuss

are all based on transporting blackwater off site,

so away from the point where it's generated

to a more centralized point where it can be treated

along with the blackwater generated by other households.

This system of blackwater treatment with effluent transport

is a little more complicated than a traditional sewer-based system

that would exist in a large European city

because only the effluent from the storage technology

is transported.

Each toilet or group of toilets is connected to some type

of collection and storage technology.

This produces sludge which must be periodically removed

and treated as in the previous systems.

But now, the solids-free effluent can be transported easily

through small diameter sewers without the risk of clogging.

The effluent can then be treated in a centralized treatment technology

like a constructed wetland.

The previous systems that we looked at that relied on infiltration

were not appropriate for dense areas because of the holding capacity

of the soil.

That is not the problem for this system because the effluent is transported

in impermeable pipes away from the community.

Here you can see the construction of a community scale ABR

and the solids-free sewer that connects the houses to it.

This system would be suitable for a very dense urban context

irrespective of the groundwater or soil conditions.

The solids-free sewers are being laid underneath these paving stones.

This system, "blackwater transport to semi-centralized treatment"

is the typical system for most European and North American cities.

A flush toilet generates blackwater

which is transported through a sewer to some sort of treatment.

Notice here also that the blackwater will require some sort of pre-treatment

to prevent the solids from clogging some of the more treatment systems.

Even robust systems like those based on activated sludge

should still include some sort of pre-treatment

just to ensure that no rubbish enters the treatment technology.

Effluent that is destined for discharge into the environment

could require some sort of post treatment.

This would ensure that the levels of pathogens, nutrients

or other constituents do not exceed environmental limits for the discharge.

The final slide is basically the water-based version

of the urine diversion system that we saw in the beginning.

Certainly, it's not a very common or popular system yet

but it's becoming more commonplace and it is the system that operates

in the Eawag building in Zurich.

Here you can see what the urine storage tanks in our buildings look like.

But before we can harvest the urine we need to start at the beginning

with the user interface.

The system requires a urine-diverting flush toilet.

This allows for the separation of urine and brown water

which, you remember, is the combination of feces and flush water.

The brown water is then transported through an existing sewer network

to a centralized treatment facility.

Urine does not provide a lot of volume to the overall waste water mix

but without it the nutrient quality in the brown water is much lower

and may require less treatment to meet discharge standards.

The sludge must be treated, as in the previous systems,

but because there is less liquid remember that there will also be

less flush water if urine is not flushed,

the sludge may be thicker and easier to dry.

The urine, of course, can be used directly after a sufficient storage period.

However, because this system is best suited to dense areas or buildings

the large volume of urine may be difficult to use locally

or alternatively, transported to where it's needed.

We covered a lot of material in this module on sanitation systems.

But the key points are simple:

We can use system templates to help design complete, logical systems

that do not skip any products or processing.

A system template is essentially a matrix of products and functional groups

with specific technologies at the intersection point.

There are nine different system templates that can be used to generate

hundreds of possible systems,

and realistically, there could be other system templates

but these are the ones that we work with at Sandec.

Although the system templates can help in the initial phases,

they must be used in conjunction with good engineering

and local understanding.

In Module 4 you will see and examine some different case studies

in which sanitation systems either worked out fairly well

or, sometimes...not so well.

Looking forward to seeing you then.

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