لخّصلي

Chlorides Chloride is a constituent of concern in wastewater as it can affect the final reuse applications of treated wastewater.The oxidation states of nitrogen tire summarized (Sawyer et al., 2003)Chlorides in natural water result from the leaching of chloride containing rocks and soils with which the water comes in contact, and in coastal areas from saltwater intrusion.In addition,agricultural, industrial, and domestic wastewaters discharged to surface waters are a source of chlorides.The production of nitrogen from the atmosphere is termed nitrogen fixation.Because fixation is a biologically mediated process and because NaN03deposits are relatively scarce, most sources of nitrogen in soil/groundwater are of biological origin.Alkalinity Alkalinity in wastewater results from the presence of the hydroxides [OH ], carbonates [C03 1, and bicarbonates [HCOf ] of elements such as calcium, magnesium, sodium, potassium, and ammonia.7 and 8.Where control of algal growths in the receiving water is necessary, removal or reduction of nitrogen in wastewater prior to discharge may be desirable.Borates, silicates, phosphates, and similar compounds can also contribute to the alkalinity.The alkalinity in wastewater helps to resist changes in pH caused by the addition of acids.Sodium nitrate (NaNO,) is found principally in mineral deposits in Chile and in the manure found in sea birds' rookeries.Because conventional methods of waste treatment do not remove chloride to any significant extent, higher than usual chloride concentrations can be taken as an indication that a body of water is being used for waste disposal.Nitrogen The elements nitrogen and phosphorus, essential to the growth of microorganisms, plants, and animals, are known as nutrients or biostimulants. 6 and 7, respectively), in biological nutrient removal (see Chap.Of these, calcium and magnesium bicarbonates are most common.

Chlorides
Chloride is a constituent of concern in wastewater as it can affect the final reuse applications
of treated wastewater. Chlorides in natural water result from the leaching of chloride containing rocks and soils with which the water comes in contact, and in coastal areas from
saltwater intrusion.In addition,agricultural, industrial, and domestic wastewaters discharged
to surface waters are a source of chlorides.
Human excreta, for example, contain about 6 g of chlorides per person per day. In areas
where the hardness of water is high, home regeneration-type water softeners will also add
large quantities of chlorides. Because conventional methods of waste treatment do not remove
chloride to any significant extent, higher than usual chloride concentrations can be taken as an indication that a body of water is being used for waste disposal. Infiltration of groundwater
into sewers adjacent to saltwater is also a potential source of high chlorides as well as sulfates.
Alkalinity
Alkalinity in wastewater results from the presence of the hydroxides [OH ], carbonates
[C03 1, and bicarbonates [HCOf ] of elements such as calcium, magnesium, sodium,
potassium, and ammonia. Of these, calcium and magnesium bicarbonates are most common. Borates, silicates, phosphates, and similar compounds can also contribute to the alkalinity.The alkalinity in wastewater helps to resist changes in pH caused by the addition of acids. Wastewater is normally alkaline, receiving its alkalinity from the water supply,
the groundwater, and the materials added during domestic use. The concentration of alkalinity in wastewater is important where chemical and biological treatment is to be used (see Chaps. 6 and 7, respectively), in biological nutrient removal (see Chap. 8), and where ammonia is to be removed by air stripping (see Chap. 11 and 15).
Nitrogen
The elements nitrogen and phosphorus, essential to the growth of microorganisms, plants, and animals, are known as nutrients or biostimulants.
Trace quantities of other elements, such as iron, are also needed for biological growth, but nitrogen and phosphorus are, in most
cases, the major nutrients of importance. Because nitrogen is an essential building block in the synthesis of protein, nitrogen data will be required to evaluate the treatability of wastewater by biological processes.
Insufficient nitrogen can necessitate the addition of nitrogen to make the waste treatable. Nutrient requirements for biological waste treatment are discussed in Chaps. 7 and 8.Where control of algal growths in the receiving water is necessary,
removal or reduction of nitrogen in wastewater prior to discharge may be desirable.
Sources of Nitrogen. The principal sources of nitrogen compounds are ( 1 ) the nitrogenous compounds of plant and animal origin, (2) sodium nitrate, and (3) atmospheric nitrogen. Ammonia derived from the distillation of bituminous coal is an example of nitrogen obtained from decayed plant material. Sodium nitrate (NaNO,) is found principally in mineral deposits in Chile and in the manure found in sea birds' rookeries.
The production of nitrogen from the atmosphere is termed nitrogen fixation.Because fixation is a biologically mediated process and because NaN03deposits are relatively scarce, most sources of nitrogen in soil/groundwater are of biological origin.
Forms of Nitrogen.
The chemistry of nitrogen is complex because of the several oxidation states that nitrogen can assume and the fact that changes in the oxidation state can be brought about by living organisms.
To complicate matters further, the oxidation state changes brought about by bacteria can be either positive or negative depending upon whether aerobic or anaerobic conditions prevail.
The oxidation states of nitrogen tire summarized (Sawyer et al., 2003)