Ultraviolet light for water treatment

Drinking water is essential for life, but is a valuable and scarce commodity. Lessthan 0.01% of the planet‘s 1.4 billion cubic kilometers of water is easily accessiblefreshwater. Several global mega-trends, like population growth, urbanization andclimate change, are driving water scarcity and public concerns on water quality.According to the World Health Organization (WHO), more than two million people –many of them children – die each year of diarrhoeal diseases that are caused bywater borne pathogens. Access to safe water is one of the big challenges of ourtimes and ultraviolet light for water treatment has become an essential technologyto meet it.



Drinking water is essential for life, but is a valuable and scarce commodity. Lessthan 0.01% of the planet‘s 1.4 billion cubic kilometers of water is easily accessiblefreshwater. Several global mega-trends, like population growth, urbanization andclimate change, are driving water scarcity and public concerns on water quality.According to the World Health Organization (WHO), more than two million people –many of them children – die each year of diarrhoeal diseases that are caused bywater borne pathogens. Access to safe water is one of the big challenges of ourtimes and ultraviolet light for water treatment has become an essential technologyto meet it.

UV Water Disinfection – a Safe Method and Economic AlternativeThe first UV water decontamination was installed in Paris, France as early as 1910.Quartz glass lamps – a development that goes back to the chief developer at Heraeus,Richard Küch (1860 – 1915) - are still used today, but modern high-tech UV lampsand their early predecessors are worlds apart. Today’s UV disinfection is a wellestablishedtechnology. The method is very safe and based on profound scientificknowledge. The real challenge today is to further increase the efficiency and servicelife of the lamps.

Contaminated water can be treated with high energy UV radiation which inactivatesviruses or micro-organisms such as bacteria, yeasts, fungi or even parasites. UV watertreatment has several benefits over other disinfection processes, notably chemicalssuch as chlorine and ozone, or filtration. It does not use chemicals, which makesit environmentally friendly.

The method is not pH-dependent and does not affectthe water’s qualities, like taste, odor or color. Disinfection byproducts (DBPs) withcarcinogenic or toxic effects are not formed. An all-important advantage is the fact,that pathogens cannot build any resistance to UV light. Thus, UV inactivates evenGiardia and the chlorine-resistant Cryptosporidia. UV disinfection has low overallcapital and operating costs, and is easy to maintain and operate.

Removal of Harmful Chemicals – Advanced Oxidation with UV Micropollutants, which include such chemicals as endocrine disrupting compounds,pharmaceuticals and personal-care-products have come into public focus in recentyears and are a serious threat for drinking water quality. In order to decompose thegenerally complex structures (e.g. of steroids or antibiotics) UV radiation is combinedwith powerful chemical oxidants such as ozone or hydrogen peroxide. A processknown as advanced oxidation process (AOP).

Fertilizers, herbicides and pesticidesfrom agriculture are other examples of micropollutants that can be successfullytreated with this method, as is shown in Andijk at Holland’s largest drinking waterreservoir Ijsselmeer.

Spectrum

Ultraviolet radiation covers the wavelength range from 100 to 380 nanometers.The disinfection process uses wavelengths in the UVC range from 240 to 280nanometers, while the oxidation process uses the wavelengths down into the VUVrange below 200 nanometers.

UVC light for technical applications is usually generated by mercury lamps becauseof their high efficiency in terms of electrical energy conversion into UVC light.Commonly, there are two types of mercury lamps used: low pressure and mediumpressure lamps.

Sketch of a typical low
pressure lamp

Sketch of a typical medium
pressure lamp

Low Pressure Lamps
A low pressure lamp comprises of a quartz tube with pinched filaments, is filled withrare gas (some mbar) and mercury or amalgam. The filaments are coated with emitterpaste that facilitates escaping electrons from the filament. A voltage applied acrossthe lamp provides an electrical discharge. The power density of the discharge is low,therefore only a small portion of mercury is evaporated and enters the gas phase. Therare gas acts as a buffer gas and is necessary for maintaining the electrical discharge.Mercury atoms are ionized and excited in the discharge by electron impact. Excitedatoms emit very effectively photons with two wavelengths: 254 nm and 185 nm inthe UV range (often called spectral lines). 185 nm emission can be filtered out bychoosing quartz of suitable transmittance.

Disinfection process

The 254 nm emission is well absorbed by DNA ofall microorganisms and viruses. This absorptionleads to a destruction of the genetic structureof DNA and inhibits the transcription of itsinformation. The microorganisms and viruses arebiologically inactivated, thus 254 nm emission issuitable for disinfection purposes.

Drinking and Process Water Treatment

UV is applied in water treatment prior to consumption e.g. for drinking and processwater or afterwards in sewage plants to treat the waste water. Generally, watertreatment is performed in several stages. Usually UV water treatment is used in thesecond-to-last or last stage depending on the specific application (see chapter 3).Stages of water treatment depend on individual water quality and vary from case to case.

UV is applied in water treatment prior to consumption e.g. for drinking and processwater or afterwards in sewage plants to treat the waste water. Generally, watertreatment is performed in several stages. Usually UV water treatment is used in thesecond-to-last or last stage depending on the specific application (see chapter 3).Stages of water treatment depend on individual water quality and vary from case to case.

UV water treatment equipment can generally be classified into two groups:n closed systems for drinking and process water treatmentn open channel configuration for wastewater treatment in sewage plants.






Closed reactor systems are used for drinking and process water treatment, in order to avoid any recontamination. For drinking water, a fluence of 400 J/m² was established as a minimum requirement for effective disinfection. This minimum UVC fluence corresponds to DVGW, ÖNorm and NSF ANSI standard (class A UV system). Please refer to chapter 9 for further information.


UV water treatment is a simple, economic and reliable method, provided a good
water quality in terms of low content of organic compounds is given. Substances like iron and manganese, staining and clouding influence the water condition and the disinfection process. The absorption coefficient or transmittance of the water for UV is critical. To ensure an effective disinfection, the operating conditions must therefore be carefully monitored and controlled. Variations in the transmittance of the water can be compensated for by adjusting lamp power and/or flow rates accordingly. Thus, UV irradiance is monitored with at least one UV sensor at a representative position in the reactor to guarantee proper lamp operation.

Generally two different types are used:

• Longitudinal flow system
• Cross flow system

Typically, the reactor consists in both cases of following components:

• UV lamp
• quartz sleeve
• wiper for mechanical cleaning of quartz sleeves to protect against fouling
• UV sensor to control UV output
• power supply

Reuse Dialyzer System

A dialyzer is often referred to as an “artificial kidney.” Its function is to remove the excess wastes and fluid from the blood, when the patient’s kidneys can no longer perform that task.

Dialyzers are made of a thin, fibrous material. The fibers form a semipermeable membrane, which allows smaller particles and liquids to pass through. The dialyzer is encased in a sealed plastic cylinder about a foot long and approximately two to three inches in diameter with openings at the top and bottom. During treatment dialysate (dialysis solution) and your blood flow through the dialyzer (but they never touch). Fresh dialysate from the machine enters your dialyzer through one opening and blood enters through the other. Wastes are filtered out of your blood into the dialysate. Dialysate containing waste products leaves the dialyzer and is washed down the drain, while the cleaned blood goes back into your body.



A dialyzer is often referred to as an “artificial kidney.” Its function is to remove the excess wastes and fluid from the blood, when the patient’s kidneys can no longer perform that task.

Dialyzers are made of a thin, fibrous material. The fibers form a semipermeable membrane, which allows smaller particles and liquids to pass through. The dialyzer is encased in a sealed plastic cylinder about a foot long and approximately two to three inches in diameter with openings at the top and bottom. During treatment dialysate (dialysis solution) and your blood flow through the dialyzer (but they never touch). Fresh dialysate from the machine enters your dialyzer through one opening and blood enters through the other. Wastes are filtered out of your blood into the dialysate. Dialysate containing waste products leaves the dialyzer and is washed down the drain, while the cleaned blood goes back into your body.
Dialyzers can remain functional after more than one use, which is why many facilities reuse them. Dialyzers are reused for a certain number of times or until it no longer works efficiently, whichever comes first. Each doctor sets his or her own policy for the maximum number of reuses. Some dialysis facilities do not reuse dialyzers, and patients at those facilities are given new dialyzers for each hemodialysis session.

Patients are given the choice of whether or not to reuse their dialyzers. Facilities that reuse must follow strict guidelines to ensure the reused dialyzers are labeled with the patient’s name, cleaned properly, sterilized and working so the patient can have an optimal dialysis treatment.

How is reuse performed?

Patients only reuse their own dialyzer, meaning that no other patient has or will ever use it. Dialyzers are never shared between patients. After your dialysis session is complete, a facility member (either your renal nurse or a patient care technician) will take you off the dialysis machine and seal your dialyzer, which is labeled with your name, in a plastic bag. The dialyzer is then sent to a reuse technician who will follow strict procedures to make sure your dialyzer is clean, sterile and in good working condition before you use it again.

The reuse technician will first do a visual inspection of the dialyzer for blood or fiber clots. The technician will also note the number of times the dialyzer has been used. If the dialyzer is due to be replaced, the technician will replace it with a new one in the size prescribed by the physician. If the dialyzer can be reused, the technician will place it into the reuse machine to start the cleaning process.

The reuse machine cleans the dialyzer using water treated with reverse osmosis. This water is highly purified and cleans the dialyzer without leaving traces of particles and chemicals. After cleaning, the machine performs a pressure test and blood volume test. The pressure test checks for any holes in the dialyzer. The blood volume test ensures that the dialyzer’s capacity is above 80% of the dialyzer’s stated size. If there are any holes in the dialyzer, or if the blood volume is less than 80% of the dialyzer’s size, it is replaced with a new one. If any problems are detected during the reuse test, the reuse machine indicators let the reuse technician know, and the dialyzer is disposed of in the proper manner.

After the reuse machine has cleaned and tested the dialyzer, it will then be filled with disinfectant and stored for at least 11 hours. Just before the patient’s next dialysis treatment, the dialyzer is rinsed with saline solution until all disinfectant is removed. A test is performed to make sure no disinfectant is left in the dialyzer. Once it is tested, the dialyzer is ready to use for the dialysis treatment.


Is reuse safe?

Various studies have examined the issue of reuse. These studies have found that the mortality rate between patients who reuse dialyzers and patients who do not was the same.
Dialysis facilities that reuse dialyzers must follow strict guidelines set forth by the Association for the Advancement of Medical Instrumentation (AAMI). The AAMI guidelines make provisions for patient safety, among them:

• A dialyzer must be clearly labeled with the patient’s name and only used for the same patient.
• A dialyzer must be tested after each use to make sure it is working properly.
• A dialyzer must be tested after rinsing for any traces of disinfectant that may remain.
• Patients must be monitored for any reactions due to reuse.

Does reuse affect dialysis outcomes?

Different factors can affect your Kt/V and URR (urea reduction ratio), standard measures of how effective your dialysis treatments are. Although reuse may affect Kt/V and URR levels, following the correct standards of reuse for monitoring fiber volumes and testing the reuse dialyzers makes this a rare issue. If you are on reuse and are concerned about your Kt/V or URR levels, talk to your renal nurse and your kidney doctor.

What are the advantages of reuse?

Reuse can be helpful to the patient and to the planet.
Patient advantages of reuse Since each dialyzer is inspected by a reuse technician, the technician can note any blood clots in the dialyzer and alert a renal nurse. Blood clots could mean you are not getting enough heparin, which is a medicine given before and throughout hemodialysis. Heparin thins the blood to allow it to pass easily through the dialyzer and prevent it from clotting, which would reduce the dialyzer’s ability to remove wastes and fluid. Blood clots in the dialyzer may make your dialysis session less effective and can lower your Kt/V.

Environmental advantages of reuse

Dialyzer reuse helps to reduce negative environmental consequences in several ways. On average, it only takes 9.6 reuse dialyzers to treat one patient for one year, versus an average of 153 single-use dialyzers. The reuse of all dialyzers in a single year would eliminate the production of up to 46 million dialyzers and reduce the amount of medical waste ending up in landfills by more than 62 million pounds.

Dialyzer reuse also reduces the amount of harmful toxins created by waste processing. In order to be properly disposed of, dialyzers first have to go through a decontamination process requiring they either be incinerated or microwaved before being sent to landfills. When dialyzers are incinerated, the process produces emissions and ash that have negative health effects on the surrounding communities. While the microwave process does not produce harmful toxins, it does nothing to reduce the amount of medical waste that ends up in landfills.

By choosing dialyzer reuse, you can dramatically reduce the negative impact on the environment. Dialyzer reuse reduces your carbon footprint, helps relieve America of its dependence on crude oil, sends less non-biodegradable waste to landfills and ultimately benefits the dialysis patient by keeping costs lower without compromising clinical outcomes.

Interesting about this product?

Call : PT. Tirta Teknosys, with Hospital Division : (021) 9897 1156 or 0813 1526 2722
Download Brochure here:

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Extended Aeration System

The first stage in the treatment process is screening. Screening iscarried out using a static stainless steel retaining screen. Removal of solids isessential and results in higher treatment efficiencies for downstream biologicalsystem. Screening also ensures safety for transfer pumps which otherwisewould ultimately clog. The wastewater after screening enters an aeratedequalization tank.

The equalization tank is aerated by fine pore subsurface diffusers to preventsettling of solids and also to build up the dissolved oxygen level in thewastewater. Aeration ensures complete mixing of the wastewater and thesolids are maintained in suspension. Settling of solids could lead toaccumulation and stagnation, leading to anaerobic and septic conditions, theresult being strong odor problems. Aeration also aids in maintaining a residual dissolved oxygen level in the wastewater, which aids in treatmentefficiency.

Equalization pumps (one operating and one-100% standby) transferwastewater from the equalization tank to the extended aeration tank. Air-liftpumps are used for equalization pumps, up to a flow of 10,000gal/day. Theextended aeration process is a suspended growth biological treatmentprocess wherein the micro-organisms grow in the suspended form. A higherlevel of micro-biological population is maintained in the tank. The aerationtank is continuously aerated with fine pore subsurface AIRMAX diffusers. Theentire process is aerobic in nature.

Micro-organisms in their endogenous phase of respiration receive less food incomparison to the food available. This process is more popularly termed as“cannibalism”. Micro-organisms eventually consume themselves when notadequate food is available. The organic matter is consumed and biologicallydegraded to stable end products.

Extended aeration processes are very popular for sewage treatmentapplications. Waterworks has EA systems operating around the globe for thisapplication in remote camp sites, hotels, hospitals and resorts.Wastewater after extended aeration treatment flows by gravity to thesecondary clarifier. The biomass settles by gravity and the supernatantoverflows the weirs to the adjoining chlorine contact tank.

The settled biomassis air-lifted and recycled to the extended aeration tank to maintain thepopulation of biomass. The extended aeration tanks is operated at a MLSSlevel of 3000 to 3500 mg/L.

The food to micro-organism ratio is maintainedbetween 0.1 and 0.15 When the biomass concentration exceeds the required MLSS level in theextended aeration tank, sludge is wasted to the sludge holding tank.

Thesludge tank is an aerated tank where the waste biomass is held and aeratedcontinuously. In the absence of any organic matter entering the sludge tank,the biomass digests itself thereby concentrating and thickening itself.

The chlorine contact tank is a baffled tank to promote contact and mixing fordisinfection. The treated wastewater exits the chlorine contact tank.