Water supply Chemical and Biological Characteristics of Water

Water supply Chemical and Biological Characteristics of Water Ghada Kassab, Ph. D Civil Engineering Department Faculty of Engineering and Technology

Water quality Drinking water is expected to be clear, colorless, odorless, and free of harmful chemicals and pathogenic microorganisms.

Quality is described with four categories; • Physical characteristics • Inorganic chemical characteristics • Organic chemical characteristics • Biological characteristics

Inorganic and organic chemical characteristics General classification Specific constituents Inorganic chemical characteristic: PH Alkalinity Typical concentration range p. H of natural water 5 -8. 5 Alkalinity in (mg Ca. CO 3 /L) Surface water: 20 -200 Groundwater 50 -1000 Major inorganic constituents Calcium, chloride, fluoride, iron, manganese, nitrate, sodium, sulfur 1 - 1000 mg/l Minorganic constituents Cadmium, chromium, copper, lead, mercury, nickel, zinc, arsenic 0. 1 -10 g/l Naturally occurring organic compounds Naturally occurring organic matter that is measured as total organic carbon (TOC) 0. 1 -20 mg/l(SW) 0. 1 -2 mg/l (GW) Anthropogenic organic constituents Synthetic organic chemicals and Below 1 g/l up to tens of mg/l emerging chemicals of concern in industry, households, and agriculture

Chemical characteristics p. H

Acidity of water is a quantitative representation of the; • Amount of acid present in water. • Ability to neutralize strong bases.

i. It is one of the end products during the biological decomposition of organic matter available in waters- especially in wastewater. iii. Some times groundwater contains 30 -50 mg/L CO 2, 2. Acidity due to mineral acids (inorganic acids) When the effluent of some industries involved in metal processes is discharges to water streams, mineral acidity can be imparted. For example HCL HNO 3 H 2 SO 4, , etc.

Significance: 1. Corrosion water containing acidity is of great concern because of it corrosive nature, which can cause the destruction of water mains and related equipment. 2. Water Treatment In water treatment, acidity has influence on chemical treatments of water. Excess CO 2 interferes with the water softening process.

Alkalinity of water is its ability to neutralize an acid due to its CO 3, -2 HCO 3 - and OH- content of elements such as calcium, magnesium, sodium, potassium and ammonia. Total alkalinity helps to resist changes in p. H. Alkalinity is determined by titrating against a standard acid, the result is expressed in terms of calcium carbonate, mg Ca. CO 3/L. Alkalinity of terms of molar quantities equals: Where refers to concentration in moles/L

Alkalinity in terms of equivalents equals where refers to concentrations in terms of equivalents/L Equivalent is a measure of reactive capacity of a given chemical species. For example 1 M H 2 SO 4 is 2 N for acid base reactions and 1 N for sulfate precipitation. For alkalinity determination Ion Concentration (mg/l) MW (mg/mmol) n Eq. Wt (mg/ m. Eq) Concentration (m. Eq/l) Concentration (mg Ca. CO 3/l) CO 3 -2 100 60 2 30 3. 33 166. 66 (3. 33*50) HCO 3 - 110 61 1. 8 90. 2 H+ 1 1 1 OH- 1. 7 1 1. 7 Where n is the number of equivalents per mole. Which in most cases will be the oxidation state.

To convert from m. Eq/l to mg/l as Ca. CO 3, we use the conversion factor: For most natural waters with p. H from 5 -8. 5, the HCO 3 - content represent the major portion of alkalinity.

Inorganic constituents Major dissolved constituents found in water constituent source Problem in water supply Range in natural water Calcium and Surface and magnesium groundwater Above 60 mg/l can be considered nuisance as hardness Ca+ 1 -500 mg/l Mg 10 -20 mg/l (SW) 30 -40 mg/l (GW) Chloride Surface and ground water; saltwater intrusion Above 250 mg/l can impart Typical surface water salty taste. Below 50 mg/l is usually less than can be corrosive to some 10 mg/l metals. Fluoride Surface water and groundwater Toxic to humans at concentrations of 250 -450 mg; fatal at concentrations above 4 g/l For surface water with TDS concentration less than 1000 mg/l, fluoride is usually less than 1 mg/l

Major dissolved constituents found in water constituent source Problem in water supply Iron and manganese Surface water Taste threshold of iron for and many consumers is around groundwater 0. 01 mg/l. iron can impart a brownish color to laundry and bathroom fixtures. Range in natural water In oxygenated surface water, the concentration of total iron is usually less than 0. 5 mg/l in groundwater that has low bicarbonate Manganese ion can impart and dissolved oxygen, a dark brown color. At iron concentrations can concentrations around 0. 4 range from 1 -10. mg/l, manganese can impart an unpleasant taste The concentration of to the water and can stain manganese ion in laundry and fixtures. surface water and groundwater may be less than 1 mg/l

Major dissolved constituents found in water constituent source Problem in water supply nitrate Surface and groundwater can contain high concentrations for nitrate from runoff from fertilizers found in urban agricultural watersheds Very high nitrate concentrations may produce blue baby syndrome Sulfur Surface and groundwater Groundwater low in dissolved oxygen can contain reduced sulfur compounds which impart objectionable odors such as that of rotten eggs. Sulfates are also corrosive in concrete structures and pipes Range in natural water Sulfate concentrations in fresh water can approach 10 mg/l.

Biological characteristics Potable water must be free from pathogenic microorganisms, which are disease causing organisms. That include • Bacteria (basic plant unit, single cell organisms that utilize soluble food) • Viruses • Protozoan parasites (single cell animal and it is scavengers for excess bacteria) • Other organisms

Biological characteristics Because there are many different water based pathogens, monitoring and detecting all of them would require a prohibitive amount of resources. Consequently, indicator organism have been identified and are used to monitor the microbial quality. Pathogens regulated in drinking water include: 1. For protozoa • Cryptosporidium: single cell protozoan parasite commonly found in lakes and rivers. Cause gastrointestinal illness (diarrhea, vomiting and cramps). • Giaridia Lamblia: single cell protozoan parasite, lives in intestines of infected human and animals.

2. For Bacteria • Escherichia coli (e-coli) of the coliform group. E-coli was selected as indicator for the following reasons: 1. E. Coli usually inhabits the intestinal tracts of humans and other mammals. Thus the presence of e-coli is an indication of fecal contamination of the water. 2. Even in acutely ill individuals, the number of E. coli excreted in the feces outnumbers the disease producing organisms by several orders of magnitude. The large number make them easier to culture 3. The coliform group of organisms survives in natural water but does not reproduce effectively in this environment. Thus, the presence of coliforms in water implies fecal contamination rather than growth of the organisms. These organisms also survive in water better than most of the bacterial pathogens. This means that the absence of coliforms is a reasonably safe indication that pathogens are not present. 4. The coliform group of organisms is relatively easy to culture. E-coli cause diarrhea, cramps, nausea and headache.

• legionella: bacteria found naturally in the environment, usually in water. Grow best in warm wter, hot tubes, plumbing systems, cooling towers or conditioning systems. If transferred in form of aerosols and inhaled it can cause pneumonia. 3. For viruses: Enteroviruses which are group of viruses that live in intestines of infected human or animal.

Water quality standards • Designated uses • Water quality criteria • Antidegradation policy • General policies