Nitrogenous Compounds

Because of the many oxidation states of nitrogen, many nitrogenous compounds enter activated sludge processes in domestic wastewater. The diversity of compounds may vary greatly depending on the industrial discharges that contain nitrogenous waste. Examples of nitrogenous compounds that are found in industrial wastewater include analine, chelating agents, corrosion inhibitors, dairy waste, and slaughterhouse waste.

Analine is used in the manufacturing of dyes, photographic chemicals, and drugs. Some chelating agents are organic-nitrogen compounds that are used to hold metals such as copper and iron in solution. Nitrites are used in corrosion inhibitors in industrial process water. Dairy waste contains nitrogen-containing proteins, including casein, and many proteins are present in the meat and blood from slaughterhouse waste.

Domestic wastewater contains organic-nitrogen compounds and ammonium ions. Nitrogen in domestic wastewater originates from protein metabolism in the human body. In fresh domestic wastewater, approximately 60% of the nitrogen is in the organic form, such as pro-teinaceous wastes, and 40% of the nitrogen is in the inorganic form, such as ammonium ions. Organic compounds such as amino acids, proteins, and urea are the principle organic-nitrogen compounds in domestic wastewater, while ammonium ions are the principle inorganic compound in domestic wastewater.

H H NH2 cysteine

Figure 3.1 Structure of an amino acid. Regardless of the structure or size of an amino acid, all amino acids contain a carboxyl group (-COOH) and an amino group (-NH2). In an amino acid such as cyteine, an amino group can be found on the carbon (C) that is bonded to the carboxyl group.

Unless discharged by specific industries, nitrite ions and nitrate ions are not found in municipal sewer systems. Conditions within the sewer systems are not favorable for the oxidation of ammonium ions or nitrite ions; that is, nitrification does not occur.

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