Virtual water

The water footprint of a country is defined as the volume of water used for the production of the goods and services consumed by the inhabitants of the country.

Study shows that both Morocco and the Netherlands import more water invirtual form (in the form of water-intensive agricultural commodities) than they export,which makes them dependent on water resources elsewhere in the world.

Hoekstra & Chapagain - Ecological Economics (2007) 143–151.

Coal-fired power plants - Desulphurization of a solid

Sulfur in coal is either organic (usually about 60%) or inorganic (about 40%). The inorganic form is iron pyrite (FeS2) which has a higher density than coal. From grinded coal it is removed by elutriation or flotation.

The removal of organic sulfur requires a chemical reaction that is accomplished best if the coal is gasified first. Gasified coal is like natural gas.

Separation according to decreasing fall velocity

Principle of an elutriator

Lake Bourget, summer 2007

Source: SACYTOX (2004) Prototype de Système d'alerte pour les proliférations de cyanobactéries toxiques dans les lacs. Rapport Sogreah-Cereve, France.

Monitoring of biomass development of toxic alga Planktothrix rubescens (a cyanobacteria) in Lake Bourget in 2002-2003.

The methods of iron and manganese removal from water consist of transforming the dissolved forms (Fe2+ and Mn2+) by oxidation, into precipitates (Fe(OH)3 and MnO2) followed by filtration.

Oxidation can be carried out using powerful chemical oxidants like oxygen, chlorine, chlorine dioxide, ozone or potassium permanganate.

low busy

streetmedium highway

μg / g PAH contamination of fine particles : Streets and traffic

We start from the simple case of a chemostat which is a continuous stirred-tank reactor (CSTR).

For the moment we do not consider reinjecting the newly produced biomass, back into the bioreactor, after liquid-solid separation.

In that case the biomass budget simply reads:

To reach good nitrification rates, it is necessary to work at a low F/M ratio. The biomass concentration thus needs to be higher than in the conventional process. These requirements have consequences regarding the subsequent sludge manipulation options and disposal routes.

Ammonia stripping• Two-step physical-chemical method• Step 1: Raise pH to 10.5-11.5

– convert ammonium ions to ammonia gas• Step 2: Air-strip

– cascade wastewater countercurrent to air flow– ammonia gas escapes to atmosphere

• Pro: less costly, no sludge or Cl by-products• Cons: acids/bases, scale, freezing problems

Continuous Belt Filter Presses

designed to work continuously, but apparently suffer from frequent troubleshooting & work interruptions anyway (not an optimal solution). If the purpose is to operate continuously, presumably centrifuge separators would form a better choice.

Hierarchy

• Prevention

• Quantity• Quality – environmental impact

• Re-use

• Recycle

• Material recovery• Composting – Organical treatment

• Incineration with energy recovery

• Incineration without energy recovery

• Landfilling

Mercury-free neon tubes

multiple hearth furnace

Controlled landfill – Class II

Dedicated collection vehicles

Sorting of household waste

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jaar

GemiddeldeAverage

Recent evolution of the LCV (lower calorific value) of municipal solid wastes accepted at Brussels-Energy combustion plant (kcal / kg) 1996 - 2012

Reminder: 9.0 MJ / kg on this diagram would read 2150 kcal / kg

In terms of energy recovery, in the Brussels agglomeration, more and more heat value is presently lost to blue and yellow bags (selective collection of sorted municipal solid wastes) which are not reaching the combustion unit any longer.

Magnet separators

After removal of the ferromagnetic metals, other metals such as Aluminum and Copper can be separated as well. Eddy currents arise when there is relative motion between a conductor and a magnet. The illustrated configuration is a rotor generating a magnetic field with alternating polarity. The repelling force created by the eddy currents moves Al and Cu metals away from the conveyor, while all the other (non-electrically conductive) materials simply drop off by gravity at the end of the conveyor.

Separation and recovery of Aluminum using magnetic eddy currents

metallic contamination of the slags, ESP and FGD residues

SO2

Environmental monitoring of Brussels-Energy Incinerator

(mg/Nm³ dry 11% O2)