Addressing Water Contamination: Beyond Arsenic

  • Post last modified:6 October 2023
Technology Complexity Chemical Use Waste Generated Water Wasted
GEH/GFH Media  Simple  None  Low <0.1%
Reverse Osmosis  Moderate Cleaning Chemicals  Low 10.25%
Ion Exchange  High Regeneration chemicals  High 2%
Activated Alumina  High Regeneration chemicals  High 2%
Coagulation Microfiltration  High Regeneration chemicals & Coagulation Moderate 5%
Comparison of Different water treatment technologies

GEH 102 for Arsenic Removal 

The consumption of arsenic through drinking water can cause a variety of illnesses in people who are subjected to a long-term daily consumption of approx. 200 μg. Apart from skin damage which occurs very often, it can also cause a number of types of cancer, such as skin and lung cancer. Around 50 million people throughout the world are currently affected by the problems caused by arsenic. 

GEH® 102 was specially developed for the economic and effective removal of arsenic from drinking water. It is a pure, synthetic iron hydroxide with a high adsorption capacity for arsenic, and is used in a fixed bed adsoption process. 

The specific adsorption of arsenate (V) and arsenite (III) by GEH® 102 is is achieved over a broad pH-range.  

Treatment capacities of up to 300,000 bed volumes can be achieved. 

GEH 101 for Heavy Metal Removal  

Trace metals can enter the environment due to various industrial processes, traffic and the application of sewage sludge and certain pesticides. Since they cannot be decomposed naturally, these substances, which are hazardous to human beings and the environment, can accumulate in the soil, as well as in the groundwater and surface waters. 

GEH® 101 has already been successfully employed as an adsorbent for the removal of heavy metals for years. It is a pure, synthetic iron hydroxide with a high adsorption capacity and a fixed bed adsorption process to treat industrial and landfill leachates and for groundwater rehabilitation, among other things. Other applications are “reactive barriers”. 

Due to its high capacity and strong fixation of the adsorbed substances, GEH®101 is an efficient and economic solution for the removal of heavy metals in the various areas of application. 

GEH 103 for Phosphate Removal 

Phosphorous is vital to all biological organisms and plays a major role in energy metabolism. As an essential nutrient, phosphorous controls the eutrophication of bodies of water.  

Naturally, it does not occur as a pure element, but as phosphate (PO43-) and its minerals. Besides this, however, there are also human sources of phosphate, such as industrial or municipal waste water. Moreover, phosphorous leachates are released into lakes and rivers from agriculturally used areas. 

GEH® 104 has already been successfully employed as an adsorbent for phosphate removal for years. It is a synthetic iron hydroxide which, because of its purity, has a high adsorption capacity for phosphate, unlike comparative adsorber materials. 

GEH® 104 is employed in the areas of lakes and pond restoration and in the elimination of phosphate from natural outdoor pools and sewage treatment plants. 

GEH 105 for Copper and Zinc Removal 

Copper and zinc are the materials that are most frequently used on the exteriors of buildings. They are primarily used for guttering, down-pipes and to cover roofs. 

However, precipitation causes corrosion of metallic copper and zinc. Depending on the existing sewage system, the dissolved metals are directly discharged into a receiving body of water or into the connected sewage treatment plant. In this process, however, only around two-thirds of the copper and zinc are bonded in the sewage sludge. The remainder also enters the receiving body of water together with the treated waste water. 

Increased levels of concentration of these metals in bodies of water are toxic to fish and microbes. They are therefore ecologically questionable and an environmental burden. 

The only way to avoid the entry of copper and zinc into soils and bodies of water is to use adsorber systems. 

Our adsorber material has already been used in the successful removal of copper and zinc for years. Various types of GEH®  105 or GEH®  105M are employed, depending on the case of application and the requirements. 

Nitrates and Nitrites 

High nitrate (NO3) concentrations in drinking water resources present a potential risk to the health of the public.  Background nitrate concentration in surface water is usually below 5 mg/L. In Pakistan, the standard set by NIH and PCRWR is 10 mg N03 – N or 45mg/L NO3, which is consistent with the USEPA standards.   

Nitrogen is a nutrient that plants cannot live without and nitrate (NO3) is the primary source.  Due to this fact, nitrogen fertilizers are applied to crops in order to encourage healthier plant growth.  However, nitrate contamination occurs when there are more nitrates present in the soil than the plants are able to consume.  This excess nitrate can move easily through soil and rocks when carried by snowmelt, irrigation and rain, ultimately ending up in the groundwater.  Besides fertilizers, other possible sources of nitrate in groundwater include waste dumps, animal feedlots, landfills, lack of sewage disposal and defective septic tanks. Groundwater contamination is enhanced when the soil is sandy or gravely due to a high hydraulic conductivity.  In addition, contamination is more likely in areas where the water table is close to the surface, or results from seepage.   

There are two major concerns with elevated nitrate levels including Lake Eutrophication and human health.  There are ways to prevent high concentrations, but since it will take many years to see the results of improved fertilizer management, nitrate removal may be the only option for many communities. 

Nitrogen Chemistry 

Nitrogen chemistry is complicated due to its numerous oxidation states the element assumes in its compounds such as, NO3 (+5), ammonium NH4+ (-3) and nitrite NO2 (+3).  Bacterial action on organic matter, such as animal wastes, releases ammonia, which may be oxidized to nitrite by bacteria called Nitrosomonas.  Further oxidation then occurs by another bacterium known as Nitrobactor increasing the oxygen demand, which can have negative effects on the environment by lowering the dissolved oxygen content in the water. High nitrates levels are therefore always accompanied by a high coli form count. In addition to the above reactions, denitrification is competing simultaneously, which converts nitrite and nitrate ions into nitrogen gas and nitrogen monoxide when denitrifying bacteria is present.  

The nitrate ion is the most oxidized form of nitrogen and is chemically non reactive in aqueous solutions. Excess nitrate concentrations in water can cause some unintended consequences on the environment and human health. 

Unintended Consequences of Nitrates 

Eutrophication of lakes occurs due to the denitrification of nitrate, where nitrates are reduced, and produce N2 gas as the end product.  The nitrogen produced in this process is available for biological nitrogen fixation.  A few genera of blue-green algae (such as Anabaena, Nostoc and Gloeotrichia) are able to fix nitrogen and do so at the surface of the lake.  The oxygen produced by algae is prevented from diffusing into the blue-green algae by structures called heterocysts.  The heterocysts consume the oxygen and prevent nitrogen from entering the cells.  This fixation process can speed up eutrophication.  Eutrophication results in low dissolved oxygen content, high BOD (biochemical oxygen demand) and reduced sunlight penetration reaching the aquatic macrophytes.  Eutrophic lakes lack diversity and generally contain only a few thriving species many of which are bacteria and aquatic worms.  The ultimate end result is the destruction of fish habitat.  The most distinct characteristic is usually a thick blanket of blue-green algae covering the surface of the pond or lake. 

Human Health 

The major concern affecting human health pertains to infants less than six months of age.  In sufficient quantities, at nitrate concentrations exceeding 10 mg/L, the possibility of a health hazard is significant towards infants.  This health hazard is due to a bacterium that exists in their gastrointestinal tract that converts nitrate to nitrite (NO2).  The nitrite produced then reacts with hemoglobin to form methemoglobin, which does not carry oxygen.  As more and more hemoglobin is converted, the infant receives less oxygen to the brain resulting in slate blue skin, vomiting, diarrhea, mental retardation and/or suffocation leading to death.  This is a syndrome known as methemoglobinemia or “blue baby” syndrome.  After six months of age, nitrate is absorbed and secreted without conversion to toxic nitrite.  There is evidence that other health problems are associated with nitrate including stomach cancer, birth defects, hypertension, enlarged thyroid and lymphoma, but studies are conflicting and inconclusive.  

Nitrite had been found to react with amines and amides to form nitrosamines and nitrosamides, which have been found to induce cancer in rodents.  There is no other group of carcinogens known that have the ability to induce such a wide variety of tumours in organs, ranging from lung, oral, brain, skin, leukemia, bladder, to name a few.  

Nitrate Contamination Prevention 

There are several ways to prevent nitrate from entering drinking water reserves.  For example, wells need to be isolated from possible sources of contamination and situated on groundwater recharge zones compared to groundwater discharge zones to eliminate collection of run-off.  Abandoned wells need to be sealed to prevent entry of nitrates into the groundwater.  In addition, sinkholes are direct routes to an aquifer and should never be used as garbage dumps. 

For some communities it may be possible to find a new source of water from a new well, a deeper well or obtain water from a nearby waterway that has a lower concentration of nitrate.  Another possibility is to install a more effective treatment system.  However, this is not easily implemented in many parts of the world, so the best preventative measure is to improve fertilization management.  

There are several ways to control the source of contamination including reducing the residual nitrate level at the completion of the growing season when the potential is high for nitrate loss.  In addition, the quantity and timing of water and nitrogen applications should be linked closely with actual crop requirements.  There is also nitrogen in the soil, irrigation water and manure that need to be taken into account and irrigation should be minimized.  

Only now are we beginning to see the resulting contamination from agricultural chemical usage of thirty to forty years ago, the impact of the previous fifteen years is yet to be seen.  Therefore, preventative measures will not present immediate ramifications and nitrate removal is the only option. 

Nitrate Removal 

With the increasing concern of high concentrations of nitrate in drinking water, many methods have been developed in attempts to efficiently remove nitrate.  Nitrate is a stable and highly soluble ion and has a low potential for adsorption or co precipitation. These properties are what make this ion difficult to remove using conventional water treatment processes including lime softening and filtration.  The methods include reverse osmosis, ion exchange, biological denitrification, ion exchange with denitrification, catalytic reduction, chemical denitrification and electro dialysis. 

EcoTech Technology involves exchanging nitrate/nitrite ions in the water for different ions attached to the exchange resin.  The media consists of a polymer of positively charged sites that are bonded to negatively charged ions; in this case sodium chloride is generally used to charge the column.  When sodium chloride is flushed through the resin column chloride ions bind to the positively charged sites on the resin.  Then water containing nitrate is passed through the column and the nitrate ions, which are negatively charged, displace the chlorine ions on the resin.  However, the final design is based on removal of sulfates prior to the nitrates, depending on the chemical water analysis. The biggest advantage of this technology is that there is no waste disposal problem and over 99.7% water is processed for drinking. In case of reverse Osmosis the wastage could be as high as 25-75%. Moreover Reverse Osmosis requires a high-energy input in order to overcome the natural osmotic flow and thus, operating costs are much higher compared to the other processes. The design is based on a long life media that selectively removes these compounds. The resins in backwashed with saline solution and has a life of over 10 years.