Geothermal Wastewaters

Water and Soil Pollution 

Geothermal hot waters are excellent solvents. Depending on the mineral composition of the rocks they pass through and the rocks they come into contact with, they contain high concentrations of salts and heavy metals. 

The elements and elemental compounds found in geothermal resources are: Ammonia (NH4), arsenic (As), Nitrogen (N2), Copper (Cu), Bicarbonate (HCO3), Boron (B), Mercury (Hg), Zinc (Zn), Iron (Fe), Fluoride (F), Hydrogen (H), Hydrogen Sulfide (H2s), Calcium (Ca), Carbonate (CO3), Carbon Dioxide (CO2), Chloride (Cl), Lead (Pb), Lithium (Li), Magnesium (Mg), Manganese (Mn), Methane (CH4), Nickel (Ni), Potassium (K), Radon (Rn), Silicon (SiO2), Sodium (Na), and Sulfate (SO4). Effects of Geothermal Water The untreated release of heavy metals such as boron, arsenic, mercury, lead, and chromium contained in geothermal fluids negatively impacts human health, plant growth and development, and soil. Heavy metals gradually contaminate surrounding streams, groundwater resources, and soil, rendering them unusable. 

Photosynthesis and respiration, crucial for life, are disrupted in polluted waters, and the ionic balances that maintain soil dynamism are disrupted. Hot waters initially cause deoxygenation, or eutrophication, in rivers, streams, and lakes, threatening aquatic life and disrupting the ecological balance. Some geothermal resources used for energy, heat, industrial, and chemical purposes can contain high concentrations of carbon dioxide, methane, hydrogen sulfide, and radon, as well as silicon, arsenic, fluoride, and boron. Boron in Geothermal Resources Hot water resources are also a source of boron. Boron concentrations in some geothermal springs have been found to range between 275 and 284 mg/l. Boron-containing waters: Water with a very good boron content of 0.33 mg/l Water with a good boron content of 0.33-0.67 mg/l Water with a usable boron content of 0.67-1.00 mg/l Water with a questionable boron content of 1.00-1.25 mg/l (at risk) Water with a boron content of 1.25 mg/l and above is considered unsuitable. 

Concentration limits are exceeded in groundwater contaminated with geothermal water. 

Effects of Boron on Humans The limit value for boron in drinking water is 1 mg/liter. This limit is exceeded in drinking water contaminated with geothermal water. Boron enters the human body naturally through food and beverages, inhalation, and skin. Approximately 90-95% of the boron that enters the body is excreted unchanged in urine within the first 24 hours, while a very small portion accumulates in organs such as bones, nails, hair, teeth, and the liver and spleen. High doses of boron can cause symptoms of poisoning such as vomiting, diarrhea, dizziness, and tremors. Skin rashes, liver, kidney, and central nervous system abnormalities can also occur. 

Effects of Boron on Plants Plants are classified as boron-sensitive, less tolerant, and more resistant based on boron concentrations in irrigation water. Boron levels above 1.25 milligrams per liter are harmful for boron-sensitive plants, 2.50 milligrams per liter for less tolerant plants, and 3.75 milligrams per liter for tolerant plants. 

Products used in agricultural irrigation water are classified as sensitive, moderately tolerant, and tolerant based on their boron content. Sensitive products are affected by boron content between 0.33 and 1 milligram per liter. These include walnuts, black walnuts, English walnuts, Palestinian artichokes, beans, elms, plums, pears, grapevines, figs, cherries, peaches, apricots, mulberries, oranges, lemons, and grapefruits. 

Medium-tolerant crops, affected by boron content between 1 and 2 milligrams per liter, include sunflowers, potatoes, cotton, tomatoes, radishes, peas, olives, barley, wheat, corn, millet, oats, squash, bell peppers, sweet potatoes, and lima beans. Tolerant crops, affected by boron content between 2 and 4 milligrams per liter, include tamarisk, asparagus, palm trees, dates, sugar beets, beets, cooking beets, alfalfa, broad beans, onions, turnips, cabbage, lettuce, and carrots. 

The use of geothermal waters for irrigation has a negative impact on the environment due to their high boron content. If boron concentration limits are exceeded in irrigation water, the plant will die. Boron-containing soils are toxic to tree roots, preventing tree growth. Excessive amounts of boron accumulate in the soil, rendering it barren. 

Boron compacts the soil and, over time, congeals it, even rendering it unusable. The leaching of boron, along with magnesium, sodium, and potassium salts into the soil and water, disrupts the balance of flora and fauna, rendering the soil inhospitable to plant growth, reducing agricultural production. 

Arsenic in Geothermal Springs Arsenic concentrations in some geothermal springs worldwide have been detected between 8,900 and 10,700 micrograms per liter. Arsenic, found in the form of arsenoic acid or arsenic acid, readily migrates into hot springs through the oxidation of pyrite, arsenopyrite, iron, copper shale, and phosphate rocks. 

Arsenic contamination of drinking water occurs from geothermal operation wastewater. Arsenic content above the standards in drinking and utility water has a toxic effect on living organisms in the ecosystem. The arsenic concentration limit in drinking water is 10 micrograms/liter. 

What are the effects of arsenic compounds ingested above this limit for a certain period of time? Inhalation of arsenic compounds: Lung cancer. Ingestion through medications, food, and especially drinking water: Skin pigmentation changes, keratosis of fingernails and toenails, and skin cancer. 

Fluoride in Geothermal Springs In some geothermal springs, fluoride concentrations have been found to range from 50 to 430 milligrams/liter. In deep groundwater that comes into contact with fluoride-rich minerals or fluoride-containing gases under pressure, fluoride levels rise to 20-53 milligrams/liter. 

Surface water in geothermal areas can have much higher fluoride content. In drinking water: No fluoride (zero): Limited improvement occurs. Between 0 and 0.5 milligrams/liter: Tooth decay occurs. Between 0.5 and 1.5 milligrams/liter: Improves dental health and prevents tooth decay. 

Between 1.5 and 4.0 milligrams/liter: Causes dental fluorosis; mottled teeth develop. Between 4 and 10 milligrams/liter: Causes dental fluorosis and skeletal fluorosis. Above 10 milligrams/liter: Disabling fluorosis develops.