Well water with iron and manganese

Case 3 Well Water with Iron and Manganese 

This case is taken from an actual analysis conducted for an O M contract for a facility in Venezuela. The system is to take potable well water from the city and generate boiler make-up water. The water has 77 ppm (as calcium carbonate) total hardness, with 60 ppm calcium and 17 ppm magnesium. The water contains 0.5 ppm iron and 0.4 ppm manganese. The remainder of the analysis is listed below (all species listed as ppm ion)  

The softener is a 48-inch diameter unit with 35ft3 of resin. The softener will regenerate once per day with 151b/ft3 of salt. At a salt cost of 80 per ton, the sodium softener would require about 638 per month to operate. 

Projections indicate that about 3 ppm of antisealant is required to minimize scaling due to hardness. At a local cost of 4.50 per pound, the monthly cost for antisealant is 46. 

Concern With Sodium Softener Without Sodium Softener  

---

Aeration towers are often simply constructed wooden towers with or without the benefit of a forced-air draft, over which the well water is distributed. Typically, the tower holds 8 to 10 trays, each with a 3- to 4-inch (7.6-10.2 cm) bed depth of volcanic lava or coke media to provide the total 30 to 36" (76-91 cm) depth required. The lava or coke acts as a catalyst for the further precipitation of iron and manganese salts. These salts can be readily oxidized provided there is sufficient alkalinity present. If in doubt, ensure a minimum of 120 to 150 ppm total alkalinity (T Aik or M Aik) as CaC03. 

The following tables provide a detailed breakdown of the compliance of water well samples with health-based guidelines (Table 1) and aesthetic guidelines (Table 2). These results indicate that in general the water quality of domestic water wells in New Brunswick is very good. The most common water quality issues in New Brunswick are due to excessive iron and manganese in well water, which is attributable to the natural geology of the province. 

Little is known concerning the chemistry of nickel in the atmosphere. The probable species present in the atmosphere include soil minerals, nickel oxide, and nickel sulfate (Schmidt and Andren 1980). In aerobic waters at environmental pHs, the predominant form of nickel is the hexahydrate Ni(H20)g ion (Richter and Theis 1980). Complexes with naturally occurring anions, such as OH, SO/, and Cf, are formed to a small degree. Complexes with hydroxyl radicals are more stable than those with sulfate, which in turn are more stable than those with chloride. Ni(OH)2° becomes the dominant species above pH 9.5. In anaerobic systems, nickel sulfide forms if sulfur is present, and this limits the solubility of nickel. In soil, the most important sinks for nickel, other than soil minerals, are amorphous oxides of iron and manganese. The mobility of nickel in soil is site specific pH is the primary factor affecting leachability. Mobility increases at low pH. At one well-studied site, the sulfate concentration and the... 

Appropriate pretreatment techniques and/or technologies for a given RO application needs to be selected based on the quality of the influent water to be treated by RO. Some water, such as well water with low concentrations of iron and manganese, may require very little, if any, pretreatment, while other water, such as river or lake water, may require extensive pretreatment using sequenced techniques and technologies. 

Clear, unfiltered well water was used for the four tests. The absence of iron and manganese, as well as a degree of oxidizability not exceeding 5 mg. of permanganate per liter, classified it among waters responding to treatment with small quantities of ozone. The temperature of the water was 11° C. At this temperature, the coefficient of distribution of the ozone between the gaseous and aqueous phases is 0.37. 

Diatomaceous earth filtration is a well-established water treatment process. It performs well on groundwater with high concentration of iron and manganese, or on surface waters with low influent turbidity, acceptable color, and bacteria levels. Effective removals of viruses and Giardia range up to 99.95% and from 99% to 99.99%, respectively. 

---