PERMIT RATIONALE FOR REISSUANCE
Tronox LLC, Hamilton Facility
Monroe County
Hamilton, Mississippi
Water NPDES No. MS0002232
October 2024

I.	FACILITY INFORMATION

Facility Name:  Tronox LLC, Hamilton Facility
Facility Address:  40034 Tronox Road 
Hamilton, MS  39746    
Hamilton, 
Permit No.:  MS0002232
SIC:  2816
Permit Writer:  Samar Patel
EPD Branch:  Chemical Branch

II.	NATURE OF BUSINESS

Tronox manufactures Titanium Dioxide from titanium-bearing ore. The impure ore is chlorinated and the resulting titanium tetrachloride is separated from the ore while in a vapor phase and then oxidized to form titanium dioxide.

III.	EFFLUENT AND RECEIVING STREAM FLOW DATA

A.	Outfall 101 – Cooling water and storm water runoff from non-process areas that include old manganese facility, old Chlorate plant, parking areas, and wooded area south of Tronox road between the road and the ditch that leads to Ponds No.3.  Long term average flow is 0.355 MGD and the maximum 30-day average flow is 1.55 MGD.  The receiving stream for this outfall is Dose Maie Creek, which has a 7Q10 of zero.

B.	Outfall 201 – Process wastewater from titanium dioxide plant, storm water runoff from process areas, sanitary and laundry wastewater (from Internal Outfall 301), and contaminated wastewater (i.e., leachate) and storm water runoff from the existing Landfill No.1 and Landfill No.2.  The long-term average flow is 6.7 MGD and the maximum 30-day average flow is 8.8 MGD.  The receiving stream for this outfall is the Tennessee-Tombigbee Waterway, which has a 7Q10 of 200 cfs (129.26 MGD).

C.	Outfall 301 – Internal outfall going into Outfall 201 made up of sanitary and laundry wastewater.

Both outfalls are in the Tombigbee River Basin 

IV.	303(d) ISSUES

	Outfall 201 – Tennessee-Tombigbee Waterway
           7Q10 of Tennessee-Tombigbee Waterway = 129.26 MGD (200 cfs)
            Mean Annual Flow of Tennessee-Tombigbee Waterway = 2,275 MGD                  (3,520 cfs) 

There are no 303(d) issues for the site.  In October 2008, a TMDL for organic enrichment and dissolved oxygen was finalized by EPA for Tombigbee River (Aliceville Reservoir). Tronox is not subject to this TMDL. 

V.	TYPE OF WASTEWATER TREATMENT:

A.	Outfall 101 – A settling/equalization pond, identified as pond 3.

B.	Outfall 201 – Process wastewater that is not recycled or reused undergo neutralization prior to treatment in a series of settling ponds (Ponds 16, 14, 11, and 7 in order). Leachate and storm water runoff from Landfill No.1 is first routed into Pond 9 (or Ponds 11 or 14 as alternatives). No matter its entry point into the system, this wastewater will be treated with the facility’s process wastewater then be routed ultimately to Pond 7 before discharging through Outfall 201. 

The discharge of leachate and storm water collected from Landfill No.2 is routed to a 20,000-gallon storage tank. From the storage tank, the leachate will be routed to either Pond 14 or to Pond 16 to be treated with the facility’s process wastewater before discharging through Outfall 201. Storm water from the two permanently installed sedimentation basins located adjacent to the landfill is routed to either Pond 14 or to Pond 16 to be treated with the facility’s process wastewater before discharging through Outfall 201. 

C.	Outfall 301 – Sanitary and laundry waste is treated in a conventional lagoon (Pond 8)

VI.	EPA APPLICABLE CATEGORICAL GUIDELINES

The facility is classified under the Standard Industrial Classification (SIC) Code 2816 which is identified as “Inorganic Pigments”. The process waste streams generated by this facility are regulated by 40 CFR §415.223(b), “Titanium Dioxide-Chloride Process.

VII.	DATA FROM APPLICATION FORM 2C and 2F

Outfall 101:

Parameter	Unit	Maximum Daily Concentration	
Oil & Grease	mg/l	<5.0	
Chemical Oxygen Demand (COD)	mg/l	27.0	
Total Suspended Solids (TSS)	mg/l	10	
Total Phosphorous (TP)	mg/l	<0.10	
Total Kjeldahl Nitrogen (TKN)	mg/l	0.58	
Total Nitrogen (TN)	mg/l	0.70	
Nitrate + Nitrite	mg/l	0.12	
Chromium	mg/l	0.10	
Iron	mg/l	9.77	
Manganese	mg/l	4.06	
Titanium	mg/l	0.246	
pH	SU	6.54 (min) – 
9.0 (max.	
Total Residual Chlorine (TRC)	mg/l	0.38	
Cadmium	mg/l	<0.002	
Copper	mg/l	<0.006	
Lead	mg/l	<0.015	
Selemium	mg/l	<0.010	
Thallium	mg/l	<0.020	

Outfall 201:

Parameter	Unit	Maximum Daily Concentration	
Aluminum	mg/l	0.60	
Ammonia	mg/l	<0.10	
Antimony	mg/l	<0.3	
Arsenic	mg/l	<0.05	
Barium	mg/l	<1.0	
Beryllium	mg/l	<0.025	
Bis(2-ethylhexyl) phthalate	mg/l	<0.0099 	
Bis(chloromethyl) ether	mg/l	<0.0099 	
Bromide	mg/l	<1.0	
Cadmium	mg/l	<0.025	
Chemical Oxygen Demand (COD)	mg/l	100	
Chlorine, Total Residual	mg/l	0.40	
Chromium	mg/l	<0.05	
Cobalt	mg/l	<0.05	
Copper	mg/l	0.025	
Cyanide	ug/l	<0.02	
Iron	mg/l	1.9	
Lead	mg/l	<0.025	
Magnesium	mg/l	24.9	
Manganese	mg/l	22.1	
Mercury	ng/l	<0.0002	
Molybdenum	mg/l	0.084	
Nickel	mg/l	<0.2	
Nitrate+Nitrite	mg/l	0.17	
Oil & Grease	mg/l	<5.0	
pH	SU	6.55-8.98	
Phenols	mg/l	<0.02	
Phosphorous	mg/l	<0.10	
Selenium	mg/l	0.055	
Silver	mg/l	<0. 05	
Sulfate	mg/l	700	
Thallium	mg/l	<0.05	
Tin	mg/l	<0.25	
Titanium	mg/l	0.039	
Total Organic Carbon (TOC)	mg/l	2.4	
Total Organic Nitrogen 	mg/l	0.17	
Total Suspended Solids (TSS)	mg/l	34	
2,3,7,8-Tetrachlorodibenzo-P-Dioxin (TCDD)	pg/l	ND
(RL = 10 pg/l)	
Zinc	mg/l	<0.02	
Vanadium	       mg/l	0.023	

Outfall 301:

Parameter	Unit	Maximum Daily Concentration	
BOD	mg/l	<6.0	
Chemical Oxygen Demand (COD)	mg/l	16.0	
Total Organic Carbon (TOC)	mg/l	3.8	
Total Suspended Solids (TSS)	mg/l	<4.0	
Ammonia	mg/l	7.4	
Oil & Grease	mg/l	<5.0	
Fecal Coliform	Col/100 mL	400	
Color	CP units	20.0	
Bromide	mg/l	<1.0	
Phosphorous	mg/l	1.0	
Nitrate+Nitrite	mg/l	0.054	
Total Organic Nitrogen 	mg/l	0.52	
      	ND = Non-Detect, RL = Reporting Limit
	
VIII. 	WATER QUALITY LIMITATIONS BASED ON WASTELOAD ALLOCATION 

	None.

IX.	CATEGORICAL GUIDELINE LIMITATIONS CALCULATIONS

See Attachment A

X.	TOXICITY SCREENING

See Attachment B

XI.	PROPOSED FINAL LIMITATIONS 

1.	Average Permit Limitations

Outfall	Parameter	Categorical Limitation	Water Quality Limitation	Present Permit Limitation	Proposed Permit Limitation	Basis	
Outfall 101 MS002232-101	Flow1	-	-	Report (MGD)	Report
(MGD)	EJ	
	Manganese1*	-	-	1.5 mg/L
(R lbs/day)	1.5 mg/L
(R lbs/day)	PPR/ABS	
	Iron1,3			1.0 mg/l
 (66.8 lbs/day)	1.0 mg/l
(2.96 lbs/day)	NRWQS 	
	Chromium1,4	-	-	-	R mg/l
(R lbs/day)	EJ	
	Titanium1,4	-	-	-	R mg/l
(R lbs/day)	EJ	
	pH1,2
(continuous)	6.0 
(min.)	6.0 
(min.)	6.0 
(min.)	6.0 
(min.)	PPR / MSWQS 	
Outfall 201 MS002232-201	Flow1	-	-	Report (MGD)	Report
(MGD)	EJ	
	Chromium1*	48.84 lbs/day	0.042 mg/l
(2.35 lbs/day)	0.042 mg/l (2.25 lbs/day)	0.042 mg/l
(2.25 lbs/day)	PPR / ABS / MSWQS	
	Iron1,4	-	-	-	R mg/l
(R lbs/day)	EJ	
	Aluminum1,4	-	-	-	R mg/l
(R lbs/day)	EJ	
	Titanium1,4	-	-	-	R mg/l 
(R lbs/day)	EJ	
	Manganese1,4	-	-	-	R mg/l 
(R lbs/day)	EJ	
	TSS1*	186.35 mg/l
10,419.2 lbs/day		30.0 mg/l
1346 lbs/day	30.0 mg/l
1346 lbs/day	ABS / PPR	
	Chlorine1*	-	0.011 mg/l
(0.61 lbs/day)	0.011 mg/l
(0.59 lbs/day)	0.011 mg/l
(0.59 lbs/day)	PPR / ABS / MSWQS	
	pH1,2
(continuous)	6.0 
(min.)	6.0 
(min.)	6.0 
(min.)	6.0 
(min.)	PPR / MSWQS 	
Outfall (301)
MS002232-301	E.coli1,5		126 col/100ml	200 col/100 ml	126 col/100 ml	MSWQS	

2.	Maximum Permit Limitations

Outfall	Parameter	Categorical Limitation	Water Quality Limitation	Present Permit Limitation	Proposed Permit Limitation	Basis	
Outfall 101
MS002232-101	Flow1	-	-	Report (MGD)	Report
(MGD)	EJ	
	Manganese1*	-	-	3.0 mg/L
(R lbs/day)	3.0 mg/L
(R lbs/day)	PPR/ABS	
	Iron1,3			2.0 mg/l
(133.6 lbs/day)	2.0 mg/l
(5.92 lbs/day)	EJ/
NRWQS	
	Chromium1,4	-	-	-	R mg/l
(R lbs/day)	EJ	
	Titanium1,4	-	-	-	R mg/l
(R lbs/day)	EJ	
	pH1,2 (continuous)	9.0
(max.)	9.0
(max.)	9.0
(max.)	9.0
(max.)	PPR / MSWQS	
	Temperature1			90ºF	90ºF	ABS / MSWQS	
Outfall 201
MS002232-201	Flow1	-	-	Report (MGD)	Report
(MGD)	EJ	
	Chromium1*	1.66 mg/l
92.80  lbs/day	0.323 mg/l
18.06 lbs/day	0.323 mg/l
17.3 lbs/day	0.323 mg/l
17.3 lbs/day	PPR / ABS	
	Iron1,4	-	-	-	R mg/l
(R lbs/day)	EJ	
	Aluminum1,4	-	-	-	R mg/l
(R lbs/day)	EJ	
	Titanium1,4	-	-	-	R mg/l
(R lbs/day)	EJ	
	Manganese1,4	-	-	-	R mg/l 
(R lbs/day)	EJ	
	TSS1*	669.70 mg/l
33,444 lbs/day	-	45.0 mg/l
2019 lbs/day	45.0 mg/l
2019 lbs/day	PPR / ABS	
	Chlorine1*	-	0.019 mg/l
1.06 lbs/day	0.019 mg/l
1.02 lbs/day	0.019 mg/l
1.02 lbs/day	PPR / ABS / MSWQS	
	pH1,2 (continuous)	9.0
(max.)	9.0
(max.)	9.0
(max.)	9.0
(max.)	PPR / MSWQS	
MS002232-301	E.coli 1,5			400 col/100 ml	410 col/100 ml	PPR / ABS/
MSWQS	
R = Report Only, PPR = Previous Permit Requirement, EJ = Engineering Judgment, ABS = Anti-backsliding Provisions (40 CFR §122.44(l)), RPA = Reasonable Potential Analysis, NRWQS = Environmental Protection Agency (EPA) - National Recommended Water Quality Criteria, MSWQS = State of Mississippi Water Quality Criteria for Intrastate, Interstate and Coastal Waters

* Water quality-based limitations, existing permit-based limitations and categorical limitations were evaluated as shown in the table above to determine the limits, but a most stringent of all three limits was proposed since it will be more protective of water quality and therefore placed in the permit. The proposed limits are considerably lower than the categorical and water-quality based limitations, but the permittee has demonstrated the ability to comply with these limits. Therefore, the limits originally set in the permit will not be changed during this renewal for the aforementioned parameters based on the Anti-Backsliding provisions of 11 Miss. Admin. Code Pt. 6, R. 1.1.4.A(4)(e). of Wastewater Regulations for NPDES Permits. 

1  Flow, pH, and temperature shall be monitored with a continuous recorder. All other parameters, with the   exception of fecal coliform, chlorine, and titanium shall be monitored weekly with a 24-hour composite sampling of the effluent. Fecal Coliform shall be monitored once every three months with a grab sample of the effluent. Chlorine shall be monitored annually with a 24-hour composite sampling. Titanium shall be monitored quarterly with a 24-hour composite sampling. 

2  pH limits are based on the State of Mississippi Water Quality Criteria. Since pH shall be monitored continuously at both permitted outfalls, language is also found in the permit which allows for short term unintentional excursions outside the permitted pH range as allowed by 40 CFR §401.17.

3  The chronic water quality criteria for iron at Outfall 101 is 1.0 mg/l. Water high in iron can have an unpleasant taste, and materials washed in water with high iron concentrations could stain. Therefore, the water quality-based effluent limits for iron are carried forward in the proposed permit. The maximum concentration limit is determined (using engineering judgment) by multiplying the 1.0 mg/l average limit by factor of 2 to obtain the 2.0 mg/l maximum limit. 

		The effluent shall be sampled once per week to demonstrate compliance with the monthly average and daily maximum limitations of 1.0 mg/l (2.96 lbs./day) and 2.0 mg/l (5.92 lbs./day). Mass loadings for iron are calculated using long-term average flow of 0.355 MGD reported in the application.  

4  The monitoring for chromium and titanium at Outfall 101 and iron, manganese, chromium, aluminum, and titanium at Outfall 201 is necessary to document any releases of these parameters into surface water since they are commonly found in waste streams at this type of industry. Iron and aluminum were detected consistently in the plant’s effluent. As such, the monitoring is proposed to document that iron and aluminum continue to remain at low levels.  

		Titanium has neither water quality criterion nor Preliminary Remediation Goal (PRG) set by ATSDR. The Mississippi Tier 1 Target Remediation Goal (TRG) for titanium in groundwater is 146 mg/l. Because TRGs are calculated using a similar method as the PRGs, they also represent safe levels for chronic lifetime exposures. In the application, titanium is reported 1.138 mg/l at Outfall 101 and 0.380 mg/l at Outfall 201. Since it would not be expected to cause any adverse health effects at these levels, we are relaxing the monitoring frequency of Titanium from once per month to once every three months. 

5  E.coli limitations were placed in the permit based on our State water quality standards.  Monitoring should be done at the point of discharge of the conventional lagoon and before mixing with the waste water from the settling ponds.  Monitoring frequency was based on regulations for municipal facilities with the same type of treatment and similar flow.

XII	Effluent Monitoring Requirements:

In addition to providing effluent limits as summarized above, monitoring requirements are included in the permit to determine compliance with these effluent limitations (Section 308 of the CWA and §122.44(i)). The permittee is responsible for conducting the monitoring and reporting these results to MDEQ as a means to ensure that the effluent wastewater treatment system (WTS) is functioning correctly and that the discharge complies with the effluent limits. 

Monitoring frequencies are based on the nature and effect of the pollutant, as well as a determination of the minimum sampling necessary to adequately monitor the facility’s performance. Based on engineering judgment, MDEQ elected to maintain the current monitoring frequencies for all evaluated pollutants in this permit since the applicant’s monitoring history has demonstrated the ability to consistently comply with regulatory limits of the permit.

XIII	Other Monitoring Basis

Outfall 101

Based on the effluent data provided in the application for Outfall 101, the facility failed the toxicity screening for cadmium, copper, selenium, lead, and thallium. For these parameters including those found non-detect in the effluent, the detection limit used was too high that they do exceed the water quality standards (i.e., screening levels of health based and human health (organisms only)). To determine with certainty whether water quality standards for these parameters are being violated, the facility shall perform additional monitoring using most sensitive method with lower detection limit twice per month for twelve months with 24-hour composite samples of the effluent beginning the month following the effective issuance date of the permit or until 24 samples are received. All monitoring results shall be submitted to the Mississippi Environmental Quality Permit Board no later than the 28th day of the month following the completed collection of all samples.  The NPDES permit may be modified to include cadmium, copper, selenium, lead, and thallium limits after screening is accomplished with the additional data, if justified. 
Outfall 201
1.	The facility was previously required to perform analyses for Antimony, Cadmium, Copper, Molybdenum, Nickel, Lead, Selenium, Thallium, and Vanadium at Outfall 201. Using data along with the application, the facility passed toxicity screening as determined in Attachment B of this rationale. Thus, the monitoring for these parameters has been removed from the proposed permit. 
Vanadium and Molybdenum have neither water quality criteria nor Preliminary Remediation Goal (PRG) set by ATSDR. The Mississippi Tier 1 Target Remediation Goals (TRG) for Vanadium and Molybdenum in groundwater are 256 mg/l and 183 mg/l, respectively. Because TRGs are calculated using a similar method to the PRGs, they also represent safe levels for chronic lifetime exposures. In the application, maximum values reported for Vanadium and Molybdenum are 0.023 mg/l and 0.084 mg/l at Outfall 201. It would not be expected to cause any adverse health effects at these levels.
2.	Whole Effluent Toxicity (WET): The permittee shall be required to test their effluent discharge for chronic toxicity during the permit term and shall submit those test results to the MDEQ semiannually following the completion of WET tests data collection. The chronic testing shall be conducted in accordance with Short-Term Methods for Estimating the Chronic Toxicity of Effluents and Receiving Waters to Freshwater Organisms, (EPA/600/4-89/001) or the most recent edition. The sampling frequency during effluent characterization shall be at least twice per year and sampling shall be timed to cover the seasonal extremes of the year such as hot-dry and cold-wet. The monitoring frequency shall be reevaluated at the next permit renewal, if provided the IC25 is greater and equal to 6.37%.
XIII	ADDITIONAL SUBMITTAL REQUIREMENT:

-	An updated facility-wide Storm Water Pollution Prevention Plan (SWPPP will be required within 180 days from permit issuance date. The revised SWPPP must identify all activities including the landfills and significant materials which may potentially pollute storm water discharges. The SWPPP shall describe and ensure implementation of Best Management Practices (BMPs), which will help minimize pollutants in storm water discharges and assure compliance with the terms and conditions of the proposed permit. The SWPPP shall, at a minimum, contain the requirements of 40 CFR 122.26(c)(1)(i)(A)-(D).

ATTACHMENT A

CATEGORICAL GUIDELINE LIMITATIONS CALCULATIONS

Federal Effluent Guidelines Calculations
Outfall 201

BAT - Maximum Daily Limitation
				
	Titanium Dioxide Production by the Chloride Process	
	[40 CFR 415.223(b)] 740 tons per day	= 1,628 (1000 lb./day)	
	 		 	
Parameter
 	Production Rate
(1000 lb./day)	Daily*	BAT Effluent Limit	
TSS	1,628	23	33,444
(669.70 mg/l)**	
Total Chromium	1,628	0.057	92.80
(1.66 mg/l)**	
pH	Minimum 6.0 S.U - Maximum 9.0 S.U. from all sources	
				
*  Pounds of constituent per 1000 pounds of product		
** Based on LTA – 6.70 MGD				

BAT - Average Monthly Limitation			
				
	Titanium Dioxide Production by the Chloride Process	
	[40 CFR 415.223(b)]740 tons per day	= 1,628 (1000 lb./day)	
	Production Rate
(1000 lb./day)	Daily*	BAT Effluent Limit	
Parameter
 				
TSS	1,628	6.4	10,419.20 lb./day 
(186.35 mg/l)**	
Total Chromium	1,628	0.03	48.84
(0.87 mg/l)**	
pH	Mininum 6.0 S.U - Maxiumum 9.0 S.U. from all sources	
				
* Pounds of constituent per 1000 pounds of product
** Based on LTA – 6.70 MGD		

CFR = Code of Federal Regulations
MGD = millions gallons per day
TSS = total suspended solids
LTA = long-term average flow

ATTACHMENT B

TOXICITY SCREENING