Illinois Administrative Code
Title 35 - ENVIRONMENTAL PROTECTION
Part 370 - ILLINOIS RECOMMENDED STANDARDS FOR SEWAGE WORKS
Subpart L - NUTRIENT REMOVAL
Section 370.1210 - Ammonia Control
Current through Register Vol. 48, No. 38, September 20, 2024
a) General
Ammonia control can be accomplished by physical, chemical, biological and ion-exchange techniques. These criteria contain design standards for a limited number of biological types and configurations of ammonia control systems. Other types and configuration of systems will be evaluated in accordance with Section 370.520(b).
Biological utilization of ammonia to produce nitrates is consumptive of available alkalinity in the ratio of 7.14 pounds alkalinity (as CaCO3) per pound of ammonia nitrogen (as N) oxidized. The determination of the need for added alkalinity must be calculated and included in the basis of design to be submitted with the plan documents for Agency approval. The following factors shall be taken into account in determining the amount of alkalinity to be added:
Load equalization shall be considered to limit peak loadings of ammonia from plant sidestreams or slug sources on the sewer system. For the fixed growth biological nitrification processes, the ammonia loading peaks shall be limited to 150% of the design average ammonia loading value.
b) Intermittent Sand Filters
Intermittent sand filters, used in conjunction with various primary and secondary treatment systems, may be considered for use as a biological process to convert ammonia to nitrate.
The construction details are generally as described in Section 370.940(g).
The design loading criteria following primary treatment is described in Section 370.940(e), (f) and (h) except that reduced organic loadings should be considered to insure meeting effluent ammonia limitations.
The design loading criteria following secondary treatment is described in Section 370.1130(b)(4) and (d)(3).
c) Suspended Growth Systems
Suspended growth nitrifying systems may be designed as a single stage process with combined carboneous BOD removal and nitrogenous oxygen demand reductions or as the second stage of a two-stage process following a first stage activated sludge process or other types of biological treatment such as trickling filters.
For nitrification, the oxygen requirement for oxidizing ammonia must be added to the requirement for carbonaceous BOD removal. The nitrogen oxygen demand shall be taken as 4.6 times the peak hourly ammonia (as N) content of the influent. In addition, the oxygen demands due to sidestream flows (digestion and sludge handling facilities and the like) must be considered due to the high concentrations of BOD and ammonia associated with such flows. Sufficient aeration and mixing capability shall be provided to maintain a sludge age of up to 20 days and a dissolved oxygen concentration in the aeration tank of at least 2 mg/l.
Careful consideration should be given to maximizing oxygen utilization per unit of power input. Unless flow equalization is provided, the aeration system should be designed to match the peak hourly load variation while economizing on power input.
Careful consideration shall be given in the design and selection of aeration and mixing equipment to minimize heat losses and to maintain sewage temperatures of at least 50° F in cold weather.
Where the ratio of ammonia to available alkalinity in the wastewater requires its use, chemical feed equipment shall be provided to maintain adequate alkalinity and a pH level between 7.2 and 8.4.
In addition to the requirements of Section 370.920, the following criteria shall govern the design:
The hydraulic detention time shall be a minimum of 8 hours based on the plant design average flow as determined by Section 370.520(c).
The following subsections set out criteria in addition to the requirements of Section 370.920 for the activated sludge nitrifying stage following a first stage activated sludge or fixed growth process used for carbonaceous BOD removal.
BOD5 concentration shall be limited to 20-50 mg/1.
The hydraulic detention time shall be a minimum of 6 hours based on the plant design average flow as determined by Section 370.520(c).
The following requirements in addition to subsection (c)(3) above, shall be provided:
d) Fixed Growth Systems
Nitrifying fixed growth systems may be used following activated sludge and fixed growth systems used for carbonaceous BOD removal.
In addition to the requirements of Section 370.900, the design of fixed growth systems shall take into account the peak hourly ammonia content of the influent. The design shall provide for ammonia load equalization in accordance with subsection (a)(3) above.
Adequate cover or housing of the nitrification units shall be provided and preceding systems shall be designed or upgraded to minimize heat losses to maintain sewage temperatures of at least 50° F in cold weather.
Adequate ventilation shall be provided to satisfy the oxygen demand of the process. Refer to Section 370.900(e)(5).
Chemical feed equipment shall be provided to maintain adequate alkalinity concentrations and a pH level between 7.2 and 8.4 where the ratio of ammonia to available alkalinity in the wastewater requires its use.
Settling tanks following nitrifying fixed growth systems shall be provided and designed in accordance with Subpart G. A single unit will be allowed if the applicable BOD and suspended solids effluent limitations can be met and other serious operational problems will not occur when the clarifier is temporarily out of service.
