Proper wastewater treatment methods have become crucial due to population increase in urban communities which has led to the proportional increase in the volume of wastewater and in the amount of organic waste. All disposal methods result in such unsatisfactory outcomes that remedial measures become paramount hence the development of wastewater treatment methods prior to when eventual disposal has to be commenced.
Wastewater treatment methods are designed to remove enough organic and inorganic solids from the wastewater so that it can be disposed off without infringing on the set objectives.
The advancement of self-purification of a stream can be measured by proper physical, chemical and biological laboratory tests. Similar tests are used to measure and control the progress of wastewater treatment methods.
We look at 3 of the top water treatment methods available today
Chemical Treatment Methods
Chemical treatment involves using some chemical reaction or reactions to improve the water quality. Probably, chlorination is the most commonly used chemical process. Chlorine, a strong oxidizing chemical, it is used to kill bacteria and slow down the rate of wastewater decomposition. Bacterial death is achieved when key biological processes are affected by the chlorine. Ozone is another strong oxidizing agent that has also been used as an oxidizing disinfectant.
A chemical process commonly applied in most industrial wastewater treatment processes is neutralization. Neutralization involves the addition of acid or base to adjust the pH levels back to neutrality. For instance since lime is a base it is sometimes utilized in the neutralization of acid wastes.
Coagulation involves the addition of a chemical that forms an insoluble end product through a chemical reaction, which serves to remove substances from the wastewater. Polyvalent metals are normally used as coagulating chemicals in wastewater treatment and model coagulants would include lime, some iron containing compounds like ferric chloride and alum (aluminum sulfate).
Some processes may actually be physical and chemical in nature. The use of activated carbon to ‘adsorb’ organics, for instance, involves both chemical and physical processes. Processes such as ion exchange, which involves exchanging some ions for others, are not widely used in wastewater treatment.
Physical Treatment Methods
Physical methods involve techniques where no gross chemical or biological changes are involved and physical phenomena are strictly used to treat the wastewater. These techniques may include: coarse screening to get rid of larger entrained objects and sedimentation.
In the case of sedimentation, physical phenomena involving settling of solids by gravity are permitted to operate. Normally this consists of simply holding a wastewater in a tank under dormant conditions for a short period of time, enabling the heavier solids to settle at the bottom of the tank; and removing the ‘clarified’ effluent. Sedimentation for solids separation is a very common process operation and is normally engaged at the beginning and end of wastewater treatment operations.
While sedimentation is one of the most usual physical treatment processes that are applied to achieve wastewater treatment, another physical treatment process consists of aeration. This process involves, physically adding air ordinarily to provide oxygen to the wastewater. Other physical phenomena used in treatment still consist of filtration. This involves the passage of wastewater through a filter medium to separate solids. An example would be the utilization of sand filters to further get rid of entrained solids from a treated wastewater. Certain phenomena will happen during the sedimentation process and can be advantageously used to improve the water quality further. Allowing greases or oils, for instance, to float to the surface and skimming or physically removing them from the wastewater is normally carried out as part of the general treatment process.
Biological Treatment Methods
Micro-organisms, mostly bacteria, are used in the biochemical decomposition of wastewater to stable end products. More micro-organisms are formed and a portion of the waste is converted to carbon dioxide, water and other end products. Usually, biological wastewater treatment methods can be divided into aerobic and anaerobic methods, based on availability of dissolved oxygen.
The purpose of wastewater treatment is generally to remove enough solids from the wastewater to allow the remainder to be discharged to receiving water without interfering with its proper use. The removed solids are primarily organic but may also include inorganic solids. Treatment must also be provided for the solids and liquids which are removed as sludge. Lastly, treatment to regulate odors, to decelerate biological activity; or eliminate pathogenic organisms may also be required.
Mathew Dennis of Takreer Envirotech argues that, the method of wastewater treatment is universal; the key is to understand how the end result for the customer can be achieved in the most cost effective way. “The process used would generally be conventional methods of wastewater treatment in Africa,” he said.
Takreer Envirotech is one of the leading suppliers of wastewater treatment systems which include: Grey Water systems, Car Wash Reclaim system, STP, MBR, MBBR, Dissolved Air Flotation, Multi Media Filtration, Micro filtration, and Nanotechnology “Our Systems are State of the Art products that provide a unique way of Control and Operations. We can provide systems that can be completely automated that can be remotely controlled to systems that can be controlled using conventional methods,” said Mr. Dennis.
“One significant challenge in the industry is to find sustainable ways of wastewater treatment with complete understanding on the after effect on environment. Having a larger view towards the environment is critical while designing a wastewater treatment system to ensure it has a positive effect on the Ecosystem,” he asserted.
According to CEO of Keneco Environmental Company, Mr. Kimani Rebo, all water nowadays is waste water and there is therefore a need for thorough treatment of all water to ensure safety of the users. Rebo says that most ‘strange’ skin diseases, cholera, typhoid, dysentery and cancers affecting children are due to consumption of untreated water.
“There are a few factors that should be put into consideration when deciding on how to treat your wastewater. You need to get the water tested to establish the kinds of wastes present. This will ensure your water is treated efficiently. You should also consider the use your treated wastewater will be put into. Water meant for drinking or cooking goes through a more thorough treatment process than one meant for irrigation, for example. The size of the project also determines the method to be used. A wastewater treatment plant for a residential house is less complicated as compared to that serving an entire city,” explains Mr. Rebo
Companies like Keneco are at the forefront championing for environmental preservation as one of the ways to restore clean water. This however, he admits comes with its own set of challenges. First, people are not keen on treating wastewater. “We are very quick to dirtify but not quick to clean,” he says.
There are also no willing financiers for wastewater treatment systems. “People do not look at it as a revenue industry. So nobody is willing to finance. The more you dirtify, the more costly it is to rectify the mistake. The waste that we put in the water accumulates and to remove it costs ten times more. In Africa, we are not quick to resolve that mistake.” Mr. Rebo adds. Policing of industries and the waste they channel into rivers, or reuse is another shortfall. “The water standards have already been set. It is just that we don’t follow them,” he asserts.