The process of treating water may have slight differences at various locations, based on the plant’s technology as well as the type of water that needs to be treated. Nevertheless, the basic principals are the same. The following section talks about the standard processes of water treatment.

Treatment methods of water
Flow chart

Coagulation & Flocculation

 Groundwater and surface water contain both dissolved and suspended particles. Coagulation and flocculation are used to separate the suspended solids portion from the water.Suspended particles vary in source, charge, particle size, shape, and density. Correct application of coagulation and flocculation depends upon these factors. Suspended solids in water have a negative charge and since they have the same type of surface charge, they repel each other when they come close together. Therefore, suspended solids will remain in suspension and will not clump together and settle out of the water, unless proper coagulation and flocculation is used.Coagulation and flocculation occurs in successive steps, allowing particle collision and growth of floc. This is then followed by sedimentation (see Sedimentation Chapter). If coagulation is incomplete, flocculation step will be unsuccessful, and if flocculation is incomplete, sedimentation will be unsuccessful.

 Coagulant chemicals with charges opposite those of the suspended solids are added to the water to neutralize the negative charges on non-settlable solids (such as clay and color-producing organic substances).Once the charge is neutralized, the small suspended particles are capable of sticking together. These slightly larger particles are called microflocs, and are not visible to the naked eye. Water surrounding the newly formed microflocs should be clear. If not, coagulation and some of the particles charge have not been neutralized. More coagulant chemicals may need to be added.A high-energy, rapid-mix to properly disperse coagulant and promote particle collisions is needed to achieve good coagulation. Over-mixing does not affect coagulation, but insufficient mixing will leave this step incomplete. Contact time in the rapid-mix chamber is typically 1 to 3 minutes.

Flocculation, a gentle mixing stage, increases the particle size from submicroscopic microfloc to visible suspended particles. Microfloc particles collide, causing them to bond to produce larger,visible flocs called pinflocs. Floc size continues to build with additional collisions and interaction with added inorganic polymers (coagulant) or organic polymers. Macroflocs are formed and high molecular weight polymers, called coagulant aids, may be added to help bridge, bind, and strengthen the floc, add weight, and increase settling rate. Once floc has reached it optimum size and strength,water is ready for sedimentation.Design contact times for flocculation range from 15 or 20 minutes to an hour or more, and flocculation requires careful attention to the mixing velocity and amount of mix energy. To prevent floc from tearing apart or shearing, the mixing velocity and energy are usually tapered off as the size of floc increases. Once flocs are torn apart, it is difficult to get them to reform to their optimum size and strength. The amount of operator control available in flocculation is highly dependent upon the type and design of the equipment.

 Sedimentation

Sedimentation is the process of allowing particles in suspension in water to settle out of the suspension under the effect of gravity. The particles that settle out from the suspension become sediment, and in water treatment is known as sludge. When a thick layer of sediment continues to settle, this is known as consolidation. When consolidation of sediment, or sludge, is assisted by mechanical means then this is known as thickening.In water treatment sedimentation might be used to reduce the concentration of particles in suspension before the application of coagulation, to reduce the amount of coagulating chemicals needed, or after coagulation and, possibly, flocculation. When sedimentation is applied after coagulation, its purpose is usually to reduce the concentration of solids in suspension so that the subsequent filtration can function most effectively.Sedimentation is one of several methods for application prior to filtration: other options include dissolved air flotation and some methods of filtration. Generically, such solids-liquid separation processes are sometimes referred to as clarification processes.There is a variety of methods for applying sedimentation and include: horizontal flow, radial flow, inclined plate,ballasted floc and floc blanket sedimentation. 

Filtration

 Filtration plays an important role in the natural treatment of groundwater as it percolates through the soil. It is also a major part of most water treatment. Groundwater that has been softened, or treated through iron and manganese oxidation, requires filtration to remove floc created by coagulation or oxidation processes. Since surface water is subject to run-off and does not undergo natural filtration,it must be filtered to remove particles and impurities.Filtration can be compared to a sieve or micro-strainer that traps suspended material between the grains of filter media. However, since most suspended particles can easily pass through the spaces between grains of the filter media, straining is the least important process in filtration. Filtration primarily depends on a combination of complex physical and chemical mechanisms, the most important being adsorption. Adsorption is the process of particles sticking onto the surface of the individual filter grains or onto the previously deposited materials. Forces that attract and hold particles to the grains are the same as those that work in coagulation and flocculation. In fact,coagulation and flocculation may occur in the filter bed, especially if coagulation and flocculation before filtration was not properly controlled. Incomplete coagulation can cause serious problems in filter operation.

Disinfection

Pathogenic organisms can be introduced into a veterinary clinic or animal housing facility through a variety of ways. For this reason, biological risk management (BRM) protocols are necessary to prevent, contain and eliminate the spread of disease. Disinfection protocols, when implemented correctly, can be a cost-effective means of reducing pathogenic organisms and are an important step in any biological risk management program. Prevention of disease is typically easier and more cost-effective than addressing an outbreak situation. Therefore, development and implementation of a step-by-step disinfection protocol for the control and prevention of infectious disease has become essential for farms and clinics.Disinfection protocols may vary depending on the need of the farm or clinic. No single disinfectant is adequate for all situations. Disinfection protocols used on a daily basis will differ from those needed to control an infectious disease outbreak. However, both have one component in common; thorough cleaning and washing prior to the application of any disinfectant is essential.

The purpose of this handout is to provide 1) an overview of factors to consider when developing and implementing an effective disinfection protocol, 2) an overview of chemicals used for disinfection, their advantages and limitations, and 3) essential steps of an effective disinfection protocol. Following development of a disinfection plan, it is equally important to train personnel of the proper procedures to use and safety issues involved as well as to have the steps posted in prominent locations throughout the facility to serve as a reminder of proper disinfecting techniques.Disinfecting agents are registered by the Environmental Protection Agency (EPA) as “antimicrobial pesticides” and are substances used to control, prevent, or destroy harmful microorganisms (i.e., bacteria, viruses, or fungi) on inanimate objects and surfaces. These antimicrobial products have traditionally included sanitizers, disinfectants, and sterilants. Data on a product’s chemistry, efficacy, toxicity to humans, animals and plants, and other parameters must be tested and submitted to the EPA prior to the marketing of the chemical.Chemical disinfectants can have various effects against microorganisms. Therefore, a basic understanding of the different chemical agents is important.

 Sludge Drying

The quantity of treated sewage as well as the level of their treatment results in the increasing amount of sewage sludge. On the other hand the requirements concerning the conditions of sludge neutralization and storage are growing. As a result of that new solutions regarding sludge treatment,management and utilization are in demand.Years of neglecting of the sludge issue caused that nowadays sewage treatment factories have to cope with a huge amounts of sludge which has gathered over the years of reckless sludge management. Sludge condensation and dewatering processes are no longer enough to cope with the still growing amounts of sludge or to reach the required standards. The form of the product obtained after dewatering process is hardly acceptable by several potential clients, including among others agriculture, forestry as well as power industry [1]. The product requires further transformation, more advanced treatment. This shall be the task of the sludge drying process, understood as the thermal drying process in which thermal energy is delivered to the sludge in order to evaporate water. Sludge drying process reduces mass and volume of the product, making its storage,transport,packaging and retail easier and also enables incineration or co-incineration of sludge.In view of the above, the analysis of problems connected with sludge drying is fully justified.There is even more than that. The analysis is of a great importance since there are several serious problems regarding sludge drying. Starting from high energy demand for a drying facility, the problem of the source of that energy, the problem of choice of the best method of drying (type of a drier) for particular type of sludge, through the problems regarding the organization of sludge drying process so that it was efficient and safe for the environment, and ending on the quality of product obtained after sludge drying.

Fluoridation

Fluoride has both beneficial and detrimental effects on human health. In terms of dental health, the prevalence of dental caries is inversely related to the concentration of fluoride in drinking water;while there is a dose-response relationship between the concentration of fluoride in drinking water and the prevalence of dental fluorosis. In terms of general health, in communities where drinking water and foodstuffs are excessively high in fluoride,skeletal fluorosis and bone fracture are the most relevant adverse effects. However, there are also other sources of fluoride.Processes such as desalination will remove virtually all fluoride from water. In terms of using such sources for drinking water, the implications for public health will strongly depend on local circumstances. However, the public health requirement is to maximize the beneficial effects of fluoride in drinking water supplies for caries prevention, whilst minimizing the unwanted dental and potential general health effects. The aetiology of dental caries involves the interplay on the tooth surface between certain oral bacteria and simple sugars (e.g.sucrose) derived from the diet. In the absence of those sugars in foods and drinks dental caries will not be a public health problem.However where sugar consumption is high or is increasing, dental caries will be or will become a major public health problem unless there is appropriate intervention. Removing fluoride from a local drinking water supply by desalination could potentially exacerbate an existing or developing dental public health problem.

pH Correction

The pH level of your drinking water reflects how acidic it is. pH stands for “potential of hydrogen,”referring to the amount of hydrogen found in a substance (in this case, water). pH is measured on a scale that runs from 0 to 14. Seven is neutral, meaning there is a balance between acid and alkalinity. A measurement below 7 means acid is present and a measurement above 7 is basic (or alkaline).Two home treatment methods to adjust pH are acid neutralizing filters and chemical feed pump systems injecting a neutralizing solution. An acid neutralizing filter uses a calcite or ground limestone (calcium carbonate) for normal pH correction, but could also include a blend of magnesium oxide and calcite, if the pH is very low. Since the water absorbs these minerals when it passes through the filter, the alkalinity and hardness will increase.Hardness is easily treated with a water softener that uses an ion exchange process to remove the hardness minerals. A chemical feed pump solution is made with well water and soda ash (similar to baking soda) and mixed in a solution tank. The chemical feed pump injects this high pH solution into the household piping system where it reacts with the low pH water in a retention tank.