Activated sludge wastewater treating process

An activated sludge process for treating wastewater containing ammonia as a contaminant and further other wastewater contaminants, if present, including cyanide, thiocyanate, sulfide and/or organic materials to achieve complete nitrification of said ammonia into nitrite and/or nitrate and less than complete denitrification of said nitrite and/or nitrate into free nitrogen, said process comprising

• microbially treating the wastewater in an activated sludge process in the presence of a microorganism population acclimated to the wastewater contaminants and their levels in the wastewater and including
• nitrifying microorganisms capable of converting ammonia to nitrite,
• optionally, nitrifying microorganisms capable of converting nitrite to nitrate, and
• facultative microorganisms capable of denitrifying nitrite and/or nitrate by oxidizing organic material and converting nitrite and/or nitrate to free nitrogen, under the following conditions:
• (1) controlling the sludge wastage rate to the extent that, for the wastewater fed during the treatment and at the conditions at which the treatment is operated, the sludge wastage rate
• (i) is low enough to provide and maintain a steady state population of microorganisms capable of converting ammonia to nitrite and/or nitrate, yet
• (ii) is high enough to prevent buildup of inert solids in the sludge;
• (2) controlling the hydraulic residence time of the wastewater in treatment such that the hydraulic residence time is
• (i) long enough to produce a sludge concentration that can be water/solid separated at the sludge wastage rate of (1) above,
• (ii) long enough to achieve substantially full sludge performance;
• (3) maintaining a dissolved oxygen level, on a continuous or weighted average basis, sufficiently high that microbial conversion of ammonia to nitrite and/or nitrate and of biological oxygen demand if present, to carbon dioxide and water occurs;
• (4) mixing the sludge
• (i) to the extent that the sludge mixing rate achieves utilization of sludge present during treatment so as to avoid causing a sludge growth rate which would result in exceeding the maximum allowable sludge wastage rate of (1) above,
• (ii) to the extent that the sludge mixing rate is large enough to reduce gradients in levels of bulk dissolved oxygen to a level consistent with the level of denitrification desired for the wastewater treatment, yet
• (iii) to the extent that the sludge mixing rate is below the rate at which microbial cell rupture occurs, irreversible breakup of agglomerates of sludge occurs and/or sludge/water settleability characteristics are not deteriorated;
• (5) controlling the biological oxygen demand during treatment such that
• (i) at least the stoichiometric amount of biological oxygen demand required to achieve a specified level of denitrification by microbial conversion of nitrite and/or nitrate to free nitrogen during treatment at a particular concentration of ammonia in the wastewater fed for treatment is present;
• and
• (ii) in the case of substantially no denitrification, controlling the treatment so as to simply provide a source of assimilable carbon for the microorganism population present;
• (6) controlling the pH of the treatment
• (i) in a range in which the level of free ammonia inhibitory to microorganism activity during the treatment is avoided, yet
• (ii) in a range in which the level of free nitrous acid inhibitory to microorganism activity, during treatment is avoided, yet
• (iii) in a hospitable range for microorganism growth and effective treatment of waste in the wastewater;
• and
• (7) controlling the temperature of the treatment
• (i) in a range in which the level of free ammonia inhibitory to microorganism activity during the treatment is avoided, and
• (ii) in a range in which the level of free nitrous acid inhibitory to microorganism activity during the treatment is avoided, yet
• (iii) in a hospitable range for microorganism action on and effective treatment of the waste in the wastewater.

A process for producing an acclimated population of microorganisms for treating wastewater containing ammonia as a contaminant, and further other contaminants, if present, including cyanide, thiocyanate, sulfide and/or organic materials, to achieve substantially complete nitrification of said ammonia into nitrite and/or nitrate and substantially complete denitrification of said nitrite and/or nitrate into free nitrogen, said process comprising introducing the wastewater into an activated sludge process containing a microorganism population including

• nitrifying microorganisms capable of converting ammonia to nitrite,
• optionally, nitrifying microorganisms capable of converting nitrite to nitrate, and
• facultative microorganisms capable of denitrifying nitrite and/or nitrate by oxidizing organic material and converting nitrite and/or nitrate to free nitrogen, and
• allowing the nitrifying microorganisms capable of converting ammonia to nitrite, nitrifying microorganisms capable of converting nitrite to nitrate, if present, and facultative microorganisms, each having a different growth rate, to grow and become acclimated to the level of ammonia, and other contaminants if present, by feeding the wastewater to the activated sludge system and microorganisms population at a rate sufficiently high to a stimulate microbial cell division but at a rate insufficiently high that an inhibitory level of ammonia, and other contaminants if present, in the wastewater is not reached, thereby causing the nitrifying microorganisms capable of converting ammonia to nitrite, nitrifying microorganisms capable of converting ammonia to nitrite to nitrate, if present, and facultative microorganisms to grow relatively such that the microorganism population becomes acclimated to the wastewater contaminants and their levels in the wastewater.

A process for producing an acclimated population of microorganisms for treating wastewater containing ammonia as a contaminant, and further other contaminants, if present, including cyanide, thiocyanate, sulfide and/or organic materials, to achieve substantially complete nitrification of said ammonia into nitrite and/or nitrate and less than complete denitrification of said nitrite and/or nitrate into free nitrogen, said process comprising introducing the wastewater into an activated sludge process containing a microorganism population including

• nitrifying microorganisms capable of converting ammonia to nitrite,
• optionally, nitrifying microorganisms capable of converting nitrite to nitrate, and
• facultative microorganisms capable of denitrifying nitrite and/or nitrate by oxidizing organic material and converting nitrite and/or nitrate to free nitrogen, and
• allowing the nitrifying microorganisms capable of converting ammonia to nitrite, nitrifying microorganisms capable of converting nitrite to nitrate, if present, and facultative microorganisms, each having a different growth rate, to grow and become acclimated to the level of ammonia, and other contaminants if present, by feeding the wastewater to the activated sluge system and microorganism population at a rate sufficiently high to stimulate microbial cell division but at a rate insufficiently high that an inhibitory level of ammonia, and other contaminants if present, in the wastewater is not reached, thereby causing the nitrifying microorganisms capable of converting ammonia to nitrite, nitrifying microorganisms capable of converting nitrite to nitrate, if present, and facultative microorganisms to grow relatively such that the microorganism population becomes acclimated to the wastewater contaminants and their levels in the wastewater.