Physical Treatment Systems
Screening is to remove solids through a series of bars or net. The sizes of solids removed are dependent on the size of opening employed. Screening is normally used at the beginning stage of the waste water treatment plant to remove large sizes of solids that could cause problem to the waste water treatment plant and its equipment.
Sedimentation or settling is one of the methods used in clarification. Clarification is a process of separating suspended solids from the waste water. Sedimentation allows the suspended solids to sink and settle at the bottom, thus producing clear supernatural.
Flotation is another method normally used in clarification. Flotation allows the suspended solids to float at the surface, thus producing clear subtenant. Flotation is normally mechanically-aided. One of the many flotation systems that are widely used is Dissolved Air Flotation.
Sand filtration is one of the many filtration systems that use sand as the filtration media. There can be many layers of sand with different sizes depending on the application. Sand filtration is classified as micro-filtration.
Membrane filtration uses membrane as the filtration media. Membrane filtration can produce better quality of water compare to sand filtration. Membrane filtration can be divided into ultra-filtration, nano-filtration and reverse osmosis filtration.
Evaporation is a process of converting the water component in the waste water into water vapor and then converting the water vapor back to water, therefore leaving behind the solid impurities.
Chemical Treatment Systems
Chemical oxidation is a process of oxidising the pollutants by chemical addition, therefore reducing the BOD and COD. Chemical oxidation is more effective in BOD and COD removal that the biological treatment but has higher operation cost.
Chemical precipitation is a process of converting dissolved solids into suspended solids and bonding the solids together to form bigger particles that can be easily removed by chemical addition. Chemical precipitation is normally used to remove heavy metals as well as suspended solids in the waste water.
Activated Carbon Adsorption
Activated carbon adsorption is a process of attracting and capture suspended solids onto the surface of the activated carbon. Activated carbon adsorption can be used to remove BOD, COD and suspended solids as well as some of other impurities.
Chlorination is normally employed for disinfection of the treated effluent. The process involves injecting chlorine gas or liquid into the treated effluent killing the microorganisms in it. Beside disinfection, chlorination is also one of the chemical oxidation methods.
Ozonation is a process of employing ozone gas to either disinfect the treated effluent or oxidize the pollutants in the wastewater. Ozonation is very effective in both disinfection and oxidation. However it capital, operation and maintenance costs are high.
Biological Treatment Systems
Trickling Filter is a type of attached growth biological treatment systems that is used mainly to remove BOD and COD. It can also be used to remove ammoniacal nitrogen that is present in the wastewater. A clarifier is required thereafter to separate the sludge produced from the treated effluent.
Activated Sludge is one of the many types of suspended growth biological treatment system is used to removed BOD and COD as well as ammoniacal nitrogen. Over the years, the Activated Sludge has been improved and modified into many other systems. A clarifier is required thereafter to separate the sludge produced from the treated effluent.
Extended Aeration is one of the suspended growth biological treatment systems that are modified from the Activated Sludge. It is modified to provide a more stable system and less sludge production. However, it requires bigger footprint compare to the Activated Sludge. This system also requires a clarifier to separate the sludge produced from the treated effluent.
Sequential Batch Reactor
Sequential Batch Reactor is another modified Activated Sludge system that provide smaller footprint than the Activated Sludge system. It is very versatile and can be adjusted to suit different conditions. The system is automated. This system eliminates the requirement of a clarifier.
Membrane Bioreactor combines the Activated Sludge with membrane filtration, therefore eliminates the need for a clarifier. Because this modified system is able to operate at a more concentrated condition, it reduces the size of the treatment system and the footprint is smaller than the Sequential Batch Reactor. The treatment efficiency is also higher than any other biological treatment systems.
Submerged Aerated Filter
Submerged Aerated Filter is a biological treatment system that combines the attached growth and the suspended growth. Trickling Filter media is added into the Activated Sludge to provide extra surface area for biological treatment. This reduces the size and increases the treatment efficiency.
Multistage Biological Treatment
Multistage Biological Treatment is a complex system combining two or more biological systems. It has higher treatment efficiency, more stable and can treat wider range of wastewater quality compare to any single stage biological treatment system.