Water recycling

WATER RECYCLING

Raquel Gavilán PárragaManuel Andrés Holgado Almaraz

Teresa Juan MangasLuis Francisco Mezquita

Ayla Pérez Díaz-MingoDavid Sánchez Serrano

Introduction

What is water?

Chemistry: 2 hydrogen atom jointedto a oxygem atom.Physics: Polar liquid with boilingtemperature of 100ºC that is solid below 0ºC.

Key point: Water is an essential and limited element for human life.

Introduction Why recycle water?

• Limited recourse of the planet.

Water is recycled by itself but if we contaminate just one of the step inthe water cycle, all the cycle is contaminated too.

• So this shows us the importance of recycling water.

freshwater3%

oceans water97%

Water on Earth

under-ground water31%

Lakes and rives3%

human use1%

frozen wa-ter

65%

Distribution of Freshwater

http://commons.wikimedia.org/wiki/File:Ciclodelh20.jpg

Introduction Pollution and water purification

• Water pollution affects rainfall, surface water, groundwater and the resulting degraded natural ecosystems.

• Since 1900 the population has quadrupled while water extraction has increased sixfold.

• In addition to sustainable development policies, purification systems are required to improve the quality of discharges generated by human activity.

Introduction Residual water purification

• By applying those purification treatments we remove from water most of the residuals that are present there and we achieve a reduction of the negative effect that human activities have in the nature.

• Treatments:• Physical treatments• Chemical treatments• Biological treatments

Introduction Drinking water disinfection

• Each country legally regulates the quality of water intended for human consumption.

• Water must be treated for human consumption and may require removal of dissolved substances, undissolved substances and microorganisms harmful to health.

• There are different technologies for drinking water treatment.

Introduction Water feautures

There are two important features:

Alkalinity:

Colloids: Particules of 1-100microns. Removed by coagulation or floculation.

Introduction Water feautures

• BOD (Biochemical Oxygen Demand)

Normally BOD5 is measure -> Oxygent demand after 5 days

Used to determine the degree of water pollution

Low leves of BOD does not necessarily imply little pollution.

Water Pollutants SolidsExcepting gases, all substances, either organic or inorganic, which are diluted in water are called solids

In this sense, solids or total solids (TS) are defined as any substances which remain as a solid residue in a water sample which has been heated to a temperature within 100ºC and 105ºC , evaporated and dried

According to their size we can find to different groups of total solids:




DISSOLVED SOLIDS Can be retained by a 2.0

micron pore filter Usually salts or organic

residues A filtering and drying

process is carried out to eliminate it




DISSOLVED SOLIDS TOTAL VOLATILED AND FIXED SOLIDS

Can be retained by a 2.0 micron pore filter

Usually salts or organic residues

A filtering and drying process is carried out to eliminate it

Are those solids which volatilize at a temperature of 550º C

These organic solids may be bacteria and viruses and other organic substances




DISSOLVED SOLIDS TOTAL VOLATILED AND FIXED SOLIDS SETTLEABLE SOLIDS

Can be retained by a 2.0 micron pore filter

Usually salts or organic residues

A filtering and drying process is carried out to eliminate it

Are those solids which volatilize at a temperature of 550º C

These organic solids may be bacteria and viruses and other organic substances

Solids over 10 micron in size and which sediment

These suspended solids will settle to the bottom of a conic shaped recipient

Water Pollutants Organic Residuals

Chemical oxygine demand (COD) is defined as the amount of diatomic oxygen O2 needed to oxidize that matter which is susceptible of being oxidized in a liquid sample

Is a good indicator of the amount of organic matter in water

The most common method to determinate COD consists of using potassium dichromate

Pathogens (pathogenic agents)Pathogenic agents which cause the transmission of multiple diseases

Bacteria Viruses Protozoa

Water Pollutants Mineralso High concentrations of heavy

metals can occur in some water bodies

o Zinc, mercury, manganese and lead are among the most frequently heavy metals found in water bodies

o Maximum Contaminant Level (MCL) is the highest level of a contaminant that is allowed in drinking water.

PHYSICAL & MINERALS CHARACTERISTICS CHART

for Calendar Year 2012

ConstituentAnnual Range

DetectedAnnual Average

Copper, ppm ND - 0.011 0.002Hardness,

ppm 10.0 - 29.0 19.6Iron ND - 0.071 0.018

Magnesium, ppm 0.70 - 2.00 1.35

Manganese, ppb ND - 0.010 0.003

Nickel, ppm ND - 0.003 0.000Phosphate,

ppm 0.37 - 1.38 0.92Potassium,

ppm 1.10 - 2.70 1.67Silica, ppm 5.44 - 15.72 10.46Zinc, ppm 0.074 - 0.252 0.153

Water Pollutants Nitrogen & Phosphor

Both, nitrogen and phosphor, are essential nutrients for aquatic life, but excessive amount s of any of them can produce serious problems.

The main effect of nitrogen and phosphor contamination of water is the so called Eutrophication.

This process produces an excessive growth of algae and aquatic plants which, after dying, degrade an decompose in riverbeds and reservoir funds.

Residual Water Physical Treatments

Clean water

Physical principles No new substances


Hydrocyclone• Solid-liquid separation

• Centrifugal force

• Sand and particlesheavier than water

• Conical or cylindrical


Dissolved Air Flotation

• Preconoces bassedon density

• Suspended solid andcontaminant liquids

• Microbubble injection


API oil-water separator• Oil separation

• Conventional separator:-Gravimetrical separation

• Parallel plate separator:-Higher surface-Less space


Membrane reactors

• Filtration processthrough membranes

• Submerged system

• External loop system


Adsorption

• Separating process in which some components of a liquid phase are transferred to a solid surface.

• Carbon filter

• Residual water

• Pesticides, dissolved organic matter, detergent, etc.


Filtration processes

• Granulated materials: sand

• Improve clarity and desinfect

• Slow filtration

• Fast filtration


Micro, ultra and

nanofiltration

Nanofiltration:Ions

0.01 microns membrane

pores

Microfiltration:Suspended

solids0.5 microns membrane

pores

Ultrafiltration: Macromolecules

0.1 microns membrane

pores


Reverse Osmosis• Filtration through a semi-permeable membrane with

presure• It can hold particles from 1 to 0.001 microns.

Residual Water Biological Treatments

LagoonsDamming residual water organic matter contained is

degraded by microorganismsDepending on oxigen level: Aerobic

Loop: seaweed in the lagoon (using light) produce high amount of oxygen aerobic bacteria break organic matter into inorganic compoundsused by seaweed to grow

Anaerobic organic charge is higher, so oxygen produced by seaweed is quickly

consumed anaerobic bacteria Facultative

Aerobic and anaerobic depending on water deepness The most used because of highest reduction in BOD (up to 90%)


LagoonsUsually system composed by an anaerobic and a facultative lagoon

first one reduces solid and organic matter content

second one produces high quality waterDisadvantages

large surface needed carefully land preparationlocated outdoors, and

hence subjected to weather

conditions


Biological ReactorsFIXED FILM SYSTEMS : rotary bio-reactor

•Microorganisms fixed into an inert media, water is passed through it

Biodiscs

Biocylinders

Control: Speed of the reactor Temperature Water characteristics (pH, level of

solved oxygen or organic charge).

Advantages: Low energy consumption Small land needed


Biological ReactorsANAEROBIC REACTORS

Biogas production

UASB (Upflow Anaerobic Sludge Blanket) Cylindrical reactors with an ascendant water flux

IC ( internal circulation )Two compartments: the lower one is fed with water with higher organic

charge upper one with less residues

Used for highly contaminated residual water Advantages: high efficiency small retention time cheap energy production due to biogas produced easily adapted to seasonal industries

Water Desinfection Chlorination

•Cl2 diatomic gas easily solved in water depending on pressure and temperature.

•Highly negative effects on microorganism that that live in water

Types

Marginal chlorination

Chloramination

Breakpoint Chlorination

Superchlorination and dechlorination

Advantage: long protection time

Carefulness with the doses of Cl added to water to avoid any side effect in human health or other smaller problems such as bad tastes or smells.

Water Desinfection Ozonization• Ozone (O3) oxidizes organic compounds

• Water is maintained in tanks with different compartments and ozone is injected there.

• Advantage: production of O3 is very easy (using electrical discharges)

• Disadvantages: Ozone very toxic and corrosive Cannot be used as method to prevent microorganisms over time

• This method has to be used instead of chlorination when water contains some determined substances. Example: phenols, which form chlorophenols that lead to very bad smells and tastes.

Water Desinfection UV Radiation

• Removal of organic matter by wet photochemical oxidation

• Nitrogen peroxide (NO2) is added to water, UV light used to start a reaction between organic compounds that produces their decomposition

•Disadvantages: generation of UV light energy expenses water has to be very clear maximum distance to the

UV source

• Advantages: minimize chemical compounds added to water better water quality

Engineering

Water recycling