EMAS vs ISO, Water Use Cycle and Desalination Technologies
EMAS vs. ISO: Key Differences
EMAS:
- Identifies and evaluates environmental aspects (direct and indirect). Obligatory to demonstrate.
- Requires a compliance audit.
- Requires annual improvement.
- Applies in Europe.
- Under legal bases. Is obligatory.
ISO:
- Requires only a procedure to identify environmental aspects.
- Only commitment to comply with applicable legal requirements.
- No compliance audit.
- Requires periodic improvement without a defined frequency.
- Applies internationally.
- Under no legal bases. Is recommended but not required.
Water Use Cycle
Water intake → Treatment → Water Use → Water depuration → Discharge
Water Intake (Sources of Water Supply)
Rainwater, Surface water (Lakes, rivers, and reservoirs), Groundwater [Wells (Aquifers) and Wellsprings], Seawater (Desalination), Meltwater, iceberg or icecaps, and Reuse water (not allowed in Spain).
Treatment
Transforms raw surface and groundwater into safe drinking water. Water treatment involves two types of processes: physical removal of solids (mainly mineral and organic particulate matter) and chemical disinfection (killing/inactivating microorganisms).
Water Treatment Techniques
Four techniques: Coagulation and flocculation, Sedimentation, Filtration, and Disinfection.
Water Treatment Process
Water Resource → Raw Water Storage → Mixing → Flocculation → Sedimentation → (Disinfectant) → Filtration → Clear well/Distribution.
Groundwater requires less treatment than surface water.
Desalination Plant
Desalination is the process of removing dissolved salts and minerals from seawater or brackish water. Desalination produces drinking water and concentrate (the water that contains the salts that were removed in the desalination process, which is sometimes called brine).
Sea Water
Advantages:
- Unlimited resources due to its abundance
- Constant salinity
- Known physical and chemical characteristics
Disadvantages:
- High salinity
- Corrosive
- Frequent and abundant biological fouling
- Restricted use (coastal area)
- High cost of desalination
Brackish Water
Advantages:
- Less salinity
- Less biological fouling
- Not restricted use
- Lower cost of desalination
Disadvantages:
- Limited resources
- Salinity increases with time
- Problematic elements: heavy metal, silica, etc.
Trends and Technologies
Distillation
Multi-stage Flash Distillation, Multi Effect Distillation, Vapor Compression.
Membranes
Reverse Osmosis, Microfiltration, Ultrafiltration, Nanofiltration, Electrodialysis.
Osmosis
Osmosis is a naturally occurring phenomenon and one of the most important processes in nature. It is a process where a weaker saline solution will tend to migrate to a stronger saline solution. Examples of osmosis are when plant roots absorb water from the soil and our kidneys absorb water from our blood.
The solution that is less concentrated will have a natural tendency to migrate to a solution with a higher concentration.
Reverse Osmosis
Whereas osmosis occurs naturally without energy required, to reverse the process of osmosis you need to apply energy to the more saline solution. A reverse osmosis membrane is a semi-permeable membrane that allows the passage of water molecules but not the majority of dissolved salts, organics, bacteria, and pyrogens. However, you need to ‘push’ the water through the reverse osmosis membrane by applying pressure that is greater than the naturally occurring osmotic pressure in order to desalinate (demineralize or deionize) water in the process, allowing pure water through while holding back a majority of contaminants.
When pressure is applied to the concentrated solution, the water molecules are forced through the semi-permeable membrane and the contaminants are not allowed through.
Reverse Osmosis System
Feed Water → Pre-treatment → High Pressure → RO Unit → Post-Treatment → Storing and Delivering Water → Waste Water