Disadvantages of using inappropriate water treatment technology
Often, there is a need to know the disadvantages of using an inappropriate water treatment technology. Which prompts us to make sure to choose the appropriate technology. Or combine a number of technologies to reach the maximum benefit and in accordance with the quality of the water to be treated. This is where Carewater experts come in to help you reach the optimal solution with distinguished experience in a large number of projects.
Water treatment with ion exchange technology
Ion exchange is particularly useful in industrial water treatment as the process removes toxic heavy metals and some pharmaceuticals and is also used in water softening.
Disadvantages of ion exchange as a water technology
There are many advantages to ion exchange as a water technology, depending on your wastewater treatment requirements, but be sure to read this section so that you are aware of the reality of operating ion exchange water treatment.
Regular and frequent shutdowns
The main disadvantage of ion exchange is the fact that you regularly and frequently need to shut down the plant to perform a backwash with brine to remove accumulated salts and minerals. This means you either have interrupted operations or you need another plant as a backup, doubling your capital.
Resin Replacement
Ion exchange vessels require regular inspection and unloading and loading of new exchange resin, which causes disruption to operations and means ongoing operating costs.
Compatible Resin Problem
New exchange resins must be specific to the manufacturer’s specifications, making it difficult to switch suppliers without replacing the entire system.
Microbial Growth When Not in Use
When an ion exchange water treatment plant is shut down, you can get microbial growth that can cause flow and treatment problems when the process is restarted. This increases training, labor, and operating costs.
Activated Carbon Water Treatment
Activated carbon absorbs contaminants into the internal structure of the carbon. Contaminant removal is effective but the process must be stopped regularly and the carbon replenished or replaced. Wastewater treatment is not possible once the carbon media is “exhausted”. At this point, it is sent to incineration or landfill with harmful environmental consequences. Despite these issues, the process is a popular water technology and is often used in industrial water treatment.
Disadvantages of Activated Carbon as a Water Technology
Large Carbon Footprint
GAC and PAC can have a large carbon footprint that your sustainability department may not agree with. This is because the effectiveness of the carbon decreases as it absorbs contaminants. Depending on how high your COD levels are, it often needs to be removed from the treatment tank and transported off-site for regeneration or disposal, which is very environmentally unfriendly.
High Operating Costs
Operating costs can be very high in applications where the chemical oxygen demand (COD) or contaminant load is high in industrial water treatment. This is because the carbon absorbs/filters contaminants and requires replacement once it is full, resulting in a regular ongoing cost.
Regular Intermittent Operations
During the carbon regeneration service, the plant is not running, so you either need to plan to reroute the wastewater to another plant or carbon bed (double capital expenditure) or you need to accept intermittent operations.
Risk of ineffective carbon
Careful maintenance of the carbon bed is required to ensure that the media is not left for long periods without renewal or replacement as this will cause the process to become ineffective and risk chemical oxygen demand levels or certain contaminants remaining in the effluent and causing pollution risks and environmental fines.
Growth of microorganisms
The activated carbon bed provides ideal conditions for the growth of microorganisms that can inhibit and inhibit treatment. However, this is not a problem when using an advanced oxidation process as hydroxyl radicals (·OH) will inhibit the growth of microorganisms.
Ineffective against non-absorbent organics
Activated carbon will not work on non-absorbent organics.
Water Treatment with Ozone
Ozone is a strong oxidizing agent and as a wastewater treatment it will oxidize all organics very effectively as long as the ozone is effectively mixed with the contaminated wastewater. It has proven to be effective and is probably the most common advanced oxidation process.
Hydrogen peroxide is sometimes added to this water technology to increase effectiveness but this can inhibit subsequent treatment steps and make this water unsuitable for reuse.
Disadvantages of Ozone as a Water Technology
Very high capital cost
Ozone systems have a very high capital cost due to the high risks associated with ozone gases, and the systems must be highly automated and robust.
Very high operating costs
The operating costs of running an ozone water treatment plant are also very high. Typically, 10 kWh per kilogram of ozone is used. Furthermore, purchasing oxygen is expensive. If you choose to make your own oxygen to treat ozone from air, you will only end up with 4% of the volume as ozone, which is ineffective. Furthermore, ozone has a half-life of 12 minutes, so your plant needs to use ozone within 5 minutes of producing ozone to achieve any kind of efficiency.
Difficulty in achieving even treatment
The biggest challenge facing your ozone plant is how to introduce ozone into the water evenly and with small enough bubbles to maximize the treatment period. Diffusers are often blocked by contaminants, leaving large areas of the treatment tank untreated.
Complex Chemistry
One of the major drawbacks of the ozone process is that its treatment requires complex chemistry tailored to each specific pollutant.
Inefficient Ozone Towers
Ozone towers have a transfer efficiency of 50-70%, so you almost always need another water treatment plant downstream of the ozone plant.
Ozone is extremely dangerous
An ozone system contains lethal concentrations of ozone, which means that careful detection and safety procedures are essential. This takes time to monitor the system, plan for incidents, train site personnel, and pay for related insurance. Ozone treatment also relies on the use of liquid oxygen, which is highly flammable and must comply with the fire safety requirements of the facility.
Harmful by-products
During treatment, ozone can produce harmful by-products such as bromate, which are often more harmful than the original pollutants as carcinogens.
Inlet water quality is important
Conventional advanced oxidation processes such as ozone + hydrogen peroxide (O3/H2O2) rely on the generation of hydroxyl radicals from H2O2. That acts as the oxidant of the process. The limitation is that the hydroxyl radicals produced are non-selective. They can be used when they “clean up” other water quality parameters such as organic matter, turbidity, alkalinity, and nitrite. This reduces the effectiveness of the system when oxidizing contaminants. It means that the inlet water must be of a very specific quality for the process to be effective.
Water Treatment Using Filtration Technology
Filtration is a necessary step in most industrial water treatment applications. Different sizes of filters remove particulate matter and some contaminants. The problem is that filtering out the contaminants only moves the problem along – you still have the more concentrated filtered toxic sludge to deal with.
Disadvantages of Filtration as a Water Technology
Not 100% Effective
Not all contaminants or bacteria are captured by the filtration process. Smaller particles pass through the membrane, requiring additional water treatment.
Downtime to Repair Clogged Filters
If filters in a wastewater treatment plant are not adequately maintained, they will clog and become ineffective at removing suspended particles. Maintenance intervals should be carefully considered depending on the fluctuating levels of contaminants in the wastewater passing through. Maintenance can sometimes be a hassle for the treatment and requires staff training.
UV Advanced Oxidation Water Treatment
UV Advanced Oxidation is a technology that combines the disinfecting properties of ultraviolet light with an oxidizing agent (hydrogen peroxide). The hydroxyl radicals produced by H2O2 act as the oxidizing agent for the process.
Disadvantages of UV as a Water Treatment Technology
Specialized process due to complex chemistry
Depending on the contaminants that need to be treated, the chemistry of the system can be complex. This requires specialized training and ongoing maintenance, which increases treatment costs.
Not suitable for water reuse
Inadequate dosing of hydrogen peroxide can have negative effects on subsequent treatment steps and make the treated water unsuitable for reuse.
Effectiveness depends on evenly distributing the H2O2 doses
The effectiveness of this water treatment depends on how well the H2O2 is mixed as it must be evenly distributed in the treatment tank.
Requires handling of hazardous chemicals
Hydrogen peroxide is used to calibrate the UV system, but this is a dangerous oxidizer to store and use. It requires training in precise processes, which adds cost.
Achieving low levels of contaminant reduction is expensive
Once the level of contaminant is reduced, the random nature of hydroxyl radicals prevents the process from being able to further treat the contaminant. This is because as the concentration of contaminants decreases, short-lived hydroxyl radicals may not “hit” a contaminant before it disappears. To achieve low levels of reduction, you need more hydroxyl radicals, which adds cost.
Reverse Osmosis Water Treatment
Reverse osmosis uses pressure to force water through a partially permeable membrane to separate contaminants. Unfortunately, contaminants are not destroyed during reverse osmosis, but concentrated contaminants that do not pass through the membrane are directed as a reject stream. This rejection almost always requires additional specialized treatment or is taken off-site for incineration, which is harmful to the environment.
Reverse osmosis works really well, but filters clog, causing a lot of downtime. It has high capital and operating expenses. A reverse osmosis plant can be used to treat the reverse osmosis reject stream or reverse osmosis inlet to extend the life of the membranes and prevent downtime.
Disadvantages of Reverse Osmosis as a water technology
High capital and operating expenses
Reverse osmosis systems are characterized by high capital and operating expenses. They pump water at very high pressure through filters made of cylinder-like materials.
High maintenance
Reverse osmosis systems generally require very high maintenance. Water must be pre-treated to protect the filters from clogging. Despite attempts to protect the filters, the reality is that they do clog, and when this happens, the solution to avoiding the high cost of replacing the membranes is to maintain them periodically.
Biological contamination of membranes
Although reverse osmosis treats water without chemical dosing, biocides are used to clean the filters and prevent bacteria from getting trapped in the membranes (biological contamination).
Not Environmentally Friendly
The reject stream from a reverse osmosis system contains twice the amount of salt found in seawater and is often discharged back into the ocean, with untold effects on the ecosystem.
Water Treatment Using Chemical Disinfection
Water disinfection is used to kill the microorganisms that cause diseases and stop their reproduction. This is especially important in drinking water applications. Water disinfection can be divided into two types: chemical and physical. Here we look at chemical disinfection using chlorine, chlorine dioxide, ozone, alcohol, detergents, and hydrogen peroxide. Some of these chemicals also remove COD from the water. Other chemicals added to water during the process of making it safe to drink include sodium hydroxide to adjust the pH level, and in some cases, fluoridation chemicals.
Disadvantages of Disinfection as a Water Technology
Continuous Monitoring Required
If bacteria are not completely removed, they can remain active and recontaminate the water over time. This means that a second disinfection step, such as chlorine dosing, is often needed after physical disinfection so that bacteria do not grow back in the water as they are distributed around the water supply network.
Chemical dosing can affect the taste of the water
When a chemical disinfection step is used, this can sometimes leave a residual taste and odor in the water, causing problems for consumers.
Biological Wastewater Treatment
Biological wastewater treatment is a secondary treatment step for wastewater that removes contaminants that remain after primary wastewater treatment. The biological process relies on microorganisms to naturally break down organic waste from the water.
If there is phenol or other hazardous chemicals that would kill insects, It can be placed in front of the biological process to remove the phenol, protecting the process.
Disadvantages of biological treatment as a water technology
Slow process with a large footprint
Biological wastewater treatment is a slow process and often has a large footprint, especially anaerobic digestion.
Aeration requires – high energy
Aerobic treatment requires aeration which can consume high levels of energy to operate.
Produces sludge – expensive and bad for the environment
This process also produces biosolids/sludge which requires specialized disposal, often involving incineration and landfill, which has negative environmental impacts.
It does not remove active ingredients and hazardous chemicals
Although biological treatment can remove a range of organic pollutants, some chemicals and pharmaceuticals remain in the waste after treatment.
Some chemicals kill insects
The water entering the biological process must also be carefully monitored. There are some organic pollutants that can damage biological systems, making them ineffective. This is where we can help remove chemicals such as phenol to protect insects.
How to avoid the harm of using an inappropriate water treatment technology
Choosing an organization that offers a comprehensive range of solutions
Choosing the right organization that is keen to provide continuous training for its staff. It saves you the trouble of searching and ensuring continuous development. Also, an organization that offers a variety of possible solutions allows you to choose and combine more than one technology until you reach the technology that suits the water to be treated.
Water quality analysis
Finding the right water technology begins with an analysis of what is in the water. The choice of wastewater management depends largely on the quality of the inlet water and the quality of the required waste. Typically, an on-site water treatment plant at a manufacturing facility or municipal factory consists of a series of steps responsible for different types of pollution. For example:
- Physical contaminants – suspended solids, sediments, metals.
- Chemical contaminants – industrial chemicals, pesticides, pharmaceuticals/drugs.
- Biological contaminants – bacteria, viruses, parasites.
Water analysis should be performed on parameters including chemical oxygen demand, pH, conductivity, and turbidity to determine the steps required to clean the water.
