TECHNOLOGIES TO MEET NUMERIC 

NUTRIENT CRITERIA AT FLORIDA’S 

DOMESTIC WATER RECLAMATION 

FACILITIES 

November 18, 2009
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Table of Contents

Executive Summary.........................................................................................................................2

Existing and Proposed Nutrient Standards......................................................................................4

Current Nutrient Removal Technology...........................................................................................5

Additional Technologies to Meet Proposed Numeric Nutrient Criteria..........................................5

Challenges Associated with Reverse Osmosis Systems..................................................................7

Costs to Meet the Numeric Nutrient Criteria

A Specific Case Study.........................................................................................................8

The Big Picture....................................................................................................................9

Sample of Utilities.............................................................................................................10

Conclusions....................................................................................................................................11
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TECHNOLOGIES TO MEET NUMERIC NUTRIENT

CRITERIA AT FLORIDA’S DOMESTIC WATER

RECLAMTION FACILITIES

EXECUTIVE SUMMARY

The consent decree between the US Environmental Protection Agency (EPA) and a coalition of 

environmental groups over the need to set numeric nutrient criteria (NNC) for surface waters in 

the State of Florida will have severe consequences for Florida’s wastewater utilities and the 

customers they serve. If the expected NNC to be proposed by EPA are implemented in the state’s 

water quality regulations, all Florida wastewater facilities that discharge reclaimed water to 

rivers, streams, lakes and estuaries will likely be required to meet new, very low limits on the 

discharge of total nitrogen (TN) and total phosphorus (TP). These new limits are anticipated to 

require a reduction in the current discharge of TN by 40 to 80% and TP by 90 to 95%. 

 Should the proposed numeric nutrient criteria become incorporated in the discharge permits for 

these treatment plants, Florida utilities will spend an estimated $24.4 to $50.7 billion in capital

costs for additional treatment facilities, and will incur an estimated $0.4 to $1.3 billion dollars 

per year more in increased operating costs. This corresponds to tens of billions of dollars in costs 

passed down to approximately three quarters of the individual citizens and businesses in the State 

of Florida. In addition, the treatment technologies needed to achieve these limits will potentially 

use almost 5 percent of the total electric power generating capacity in the State of Florida and 

contribute over 17.4 million tons of carbon dioxide (CO2) emissions per year.

According to the Florida Department of Environmental Protection (FDEP), there are 

approximately 2,100 permitted domestic wastewater facilities in the State with a total treatment 

capacity of about 2.4 billion gallons per day, approximately half of which discharge effluent to 

surface waters. FDEP reported in 2005 that approximately 64% of Florida’s population is served 

by central sewer systems that feed these treatment facilities. Florida’s total population is in 

excess of 18 million residents according to the US Census Bureau. Based on these figures, 

approximately 12 million citizens of Florida are served by permitted wastewater treatment 

facilities that will be impacted by the proposed NNC. 

Required facility upgrades to treat the 2.4 billion gallons of wastewater per day to the new 

standards would result in a cost of approximately $1.6 to $3.3 billion dollars per year over the 

next 30 years in addition to current treatment costs. Considering the interest paid on bonds 

required to fund these improvements, the State’s wastewater utilities are facing a $47.6 to $98.7 

billion dollar price tag to meet the proposed nutrient criteria over the next 30 years. These figures 

do not account for the corresponding increase in operating costs. We estimate that annual user 

fees for customers served by the impacted facilities will increase by an average of $673 to $726 
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per year in total. Table 1 summarizes the potential cost to Florida and the average individual 

household.

This paper addresses the anticipated costs for Florida utilities to be in compliance with EPApromulgated numeric nutrient criteria; the treatment technologies available to achieve the 

proposed criteria; and lastly, the additional $673 to $726 in yearly costs to customers should 

these regulations be adopted. 

Table 1 Summary of Estimated Project Costs and the Estimated Average Increase in 

Annual Sewer Rates for the State of Florida to Implement Numeric Nutrient 

Criteria.

Project Cost1 Annual Debt 

Service2

Increase in 

Annual 

Operating 

Costs3

Yearly Sewer 

Rate Increase 

per Customer4

Florida Facilities 

with NPDES 

Permits5

$24,400,000,000 $1,600,000,000 $433,000,000 $673

All Florida 

Facilities5 $50,700,000,000 $3,300,000,000 $1,330,000,000 $726

Notes:

1. Project costs include estimated construction costs plus contingencies, administrative, legal, engineering and financing costs. Estimates also 

assume all private facilities must be upgraded to provide advanced wastewater treatment, microfiltration, and reverse osmosis with concentrate 

drying with landfill disposal. Assumes public facilities with deep wells will construct new deep wells for concentrate disposal. All other public 

facilities assumed to construct facilities for concentrate drying.

2. Annual debt service based on 30-year amortization schedule and 5% interest. 

3. Assumes current flow is 50% of design flow, and that this is representative of "actual" usage of the plant. Capital upgrades will be required for 

the entire design flow, while operating costs are based on actual usage.

4. Average cost for public and private systems. Customer size estimated at 2.1 persons per household based on US Census information.

5. The range of project costs was based on two scenarios. The lower project cost assumes that only surface water dischargers (e.g. assumed to be 

plants with NPDES permits) would be required to comply with the proposed nutrient criteria. The higher project cost assumes that all Florida 

plants will be required to comply with the proposed nutrient criteria.
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EXISTING AND PROPOSED NUTRIENT STANDARDS

Florida’s water reclamation plants already operate within a complex system of water quality 

regulations that are among the most stringent in the world. Currently, the highest level of 

treatment provided by Florida wastewater treatment plants is Advanced Wastewater Treatment 

(AWT). In Florida, the term “AWT” is often used to refer to wastewater treatment that produces 

a reclaimed water achieving standards set out in section 403.086(4), Florida Statutes, i.e. 

reclaimed water containing no more than 5 mg/ L of carbonaceous five-day biochemical oxygen 

demand (cBOD5), 5 mg/L total suspended solids (TSS), 3 mg/L TN, and 1 mg/L TP. 

According to the proposed consent decree between EPA and a coalition of environmental groups, 

EPA is to propose NNC for fresh waters in Florida in January 2010 and marine waters by

January 2011. NNC proposed by FDEP in June 2008 would drop the TN limit from 3.0 mg/L to 

0.82 – 1.73 mg/L and TP limits from 1.0 mg/L down to 0.069 – 0.415 mg/L. Based on review 

comments from EPA on the FDEP NNC, the actual values for EPA's NNC are expected to be 

lower than the NNC proposed by the FDEP. While these proposed changes might seem small, 

the new NNC are at (for TP) or below (for TN) the concentrations achievable with proven 

nutrient removal technologies now in full-scale use at municipal wastewater plants. Table 2 

allows a comparison of the current standards for secondary and AWT standards with the 

proposed NNC standards.

The very low concentration criteria on TN and TP being proposed can be met, although at 

significant cost, by adding additional treatment processes at the end of a Florida advanced 

wastewater treatment (AWT) plant. AWT as currently practiced will not provide consistent 

compliance with the proposed NNC, and additional technologies must be employed. 

Table 2 Comparison of Maximum Pollutant Concentrations Allowed by Water 

Reclamation Standards

Pollutant Secondary Limits1 AWT Limits2 Proposed Numeric 

Nutrient Limits3

cBOD5, mg/L 20-30 5 -

TSS, mg/L 20-30 5 -

TN, mg/L No limit 3 0.82 – 1.73

TP, mg/L No limit 1 0.069 – 0.415

Notes:

1. Nationwide technology based standards required by the Clean Water Act for all wastewater treatment plants.

2. Florida standards required by state law for discharge to specific nutrient sensitive water bodies.

3. Proposed in-stream water quality standards that would become end-of-pipe limits unless a facility obtains a mixing zone or sitespecific alternative criteria.
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CURRENT NUTRIENT REMOVAL TECHNOLOGY 

Today more than 65 Florida plants with a total treatment capacity of over 500 million gallons per 

day (mgd) use various AWT technologies to produce high quality reclaimed water. However, 

these plants represent only a relatively small fraction of the plants in Florida. In order to achieve 

current AWT water quality limits, a plant generally must remove about 96% to 98% of TN and 

85 to 88% of TP from raw sewage. At nearly all AWT plants in Florida, reclaimed water meeting 

AWT limits is achieved using a combination of a biological nutrient removal (BNR) treatment 

technology plus some form of filtration. BNR processes grow naturally occurring bacteria to

remove the oxygen demanding organic pollutants, nitrogen, and phosphorus from raw sewage. 

Most of the nitrogen is released to the atmosphere as nitrogen gas while the phosphorus is 

removed with biosolids wasted from the plant.

The TN in reclaimed water consists of inorganic nitrogen (ammonia and nitrates) and organic 

nitrogen. The ammonia and nitrates can be removed down to low levels by conventional BNR 

processes – nitrification and denitrification with supplemental carbon (e.g. methanol) if 

necessary. The presence in reclaimed water of soluble nitrogen and phosphorus compounds that 

are not biodegradable (also known as refractory compounds) ultimately sets the lowest 

concentrations possible at treatment plants that rely on biological treatment methods. 

Researchers call the refractory dissolved organic nitrogen (RDON). RDON is present in many 

raw water supplies and thus is present in the influent to water reclamation facilities. RDON is 

also a byproduct of biological treatment and will be found in reclaimed water even if not found 

in raw sewage.

The effluent TN and TP concentrations reported by Florida AWT plants are generally consistent 

with the lowest effluent concentrations of TN and TP typically reported by researchers as 

achievable with current BNR technologies. In other words, Florida AWT plants are already 

removing nutrients as well or better than most BNR plants.

ADDITIONAL TECHNOLOGIES TO MEET PROPOSED NUMERIC 

NUTRIENT CRITERIA

Water treatment technologies do exist to produce reclaimed water with any desired water quality 

such as the ultra pure water required for electronics manufacturing and high-pressure boiler feed 

water. Since most technologies that can achieve these limits are typically used for applications 

other than removing nutrients from reclaimed water, little data exists on their performance in 

removing nitrogen and phosphorus to meet NNC.

The additional treatment technologies that might be used to meet numeric nutrient criteria

include high-pressure membranes (reverse osmosis and nanofiltration), adsorption (activated 
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carbon and reactive filtration), oxidation (ozone, UV, peroxide), chemical coagulation and 

precipitation, and ion exchange. 

Of the aforementioned additional treatment technologies, reverse osmosis (RO) is a leading 

candidate technology when considering very low nutrient limits because of its ability remove 

nearly all constituents in the water to very low concentrations. In simple terms, RO is a 

selectively permeable barrier that rejects nearly all contaminants larger than a specific size, while 

letting water molecules through. A number of large water reclamation plants currently use RO to 

produce very high quality reclaimed water. These include the West Basin plant in El Segundo, 

California (22.5 mgd), the Scottsdale, Arizona Water Campus (14 mgd), the GWRS (70 mgd) 

plant in Orange County California, and four NEWater plants in Singapore (Bedok, 8.4 mgd; 

Kranji, 10.6 mgd; Seletar, 5.0 mgd; and Ulu Pandan, 39.1 mgd) among others. All of these 

facilities have successfully used membrane technologies to produce exceptionally high quality 

water for other purposes than to remove nutrients. Specifically, the West Basin plant in El 

Segundo and the GWRS plant use MF/RO treated reclaimed water to create saltwater intrusion 

barriers and for indirect potable reuse. The Scottsdale plant treats to drinking water standards and 

then injects MF/RO treated water into an aquifer to supplement drinking water supplies, and the 

four NEWater plants in Singapore use MF/RO or UF/RO to create high quality industrial water 

supplies for electronics manufacturing and to provide supplemental water to a reservoir used as a 

drinking water supply.

Figure 1 provides a schematic representation of the sequence of treatment zones in the typical 

Florida water reclamation plant designed to meet AWT limits using BNR along with the selected 

additional technology of reverse osmosis membranes and associated concentrate disposal. 
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Crystallizer

Product Water

Brine

Concentrator

Microfiltration

(MF)

Reverse 

Osmosis (RO)

Solids to 

Disposal

To AOP/ 

Stabilization

Disinfection

Anoxic

Anoxic Clarifier

Aeration Aeration

Anaerobic

Filters

Advanced Wastewater Treatment (AWT)

MF/RO Concentrate Treatment

Figure 1. Schematic illustration of the type of processes likely required for Florida wastewater plants to 

comply with the proposed numeric nutrient criteria.

CHALLENGES ASSOCIATED WITH REVERSE OSMOSIS SYSTEMS

RO systems create several significant challenges. First, since membranes simply separate various 

constituents from water, RO creates a “concentrate” stream, typically 15 to 20% of the feed 

water, that contains concentrated levels of the rejected constituents. For example, if the mineral 

calcium was in the untreated water at 100 mg/L, it would be treated to nearly 0 mg/L in the 

treated stream with a concentration of about 500 mg/L in the concentrate stream that then needs 

to be disposed of. Finding economical methods that will comply with regulatory and public 

perception requirements for reuse or dispose of concentrate can be a challenge. In areas with 

suitable geology, deep well disposal is an option. Concentrate cannot be recycled upstream of an 

RO system as the salt concentration very quickly builds to intolerable levels. Concentrate can 

also be evaporated, dried, and landfilled; however, both the capital and operating costs of drying 

concentrate are on the order of $3.00 per 1000 gallons treated more expensive than other disposal 

methods. 

Another significant drawback to RO treatment is the high power cost required to operate an RO 

system. Adding RO to the typical water reclamation plant will increase power consumption for 

an already energy-intensive system by at least 90%. Power requirements for RO systems treating 

reclaimed water range from about 1,400 to 2,400 kWh per mgal treated, compared with the 
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average power consumption for existing water reclamation facilities of about 1,500 kWh/mgal. 

RO membranes also tend to foul quickly in reclaimed water applications, requiring pretreatment 

of feed water and regular chemical cleaning of the membranes, both of which increase the cost 

and complexity of building and operating an RO system. At present most reclaimed water RO 

systems use microfiltration (MF) for pretreatment.

Finally, RO treatment still needs to be preceded by a BNR process. RO alone will not remove 

ammonia and nitrate to the degree required due to their similar size and molecular characteristics 

to water. A typical RO membrane will reject about 90% of the nitrate and 95% of the ammonia 

in the feedwater. While phosphates are better removed by RO membranes (rejection ≥ 99.8%), 

too much phosphorus going to an RO system will also foul membranes as a result of the 

precipitation of insoluble phosphate compounds.

COSTS TO MEET THE NUMERIC NUTRIENT CRITERIA

A Specific Case Study

To illustrate the costs to implement additional treatment to meet the proposed numerical nutrient 

criteria, consider an existing 10 mgd Florida water reclamation plant that meets advanced 

secondary water quality standards for public access reuse. To meet the numeric nutrient criteria,

the biological portion of this plant must be upgraded to meet AWT limits, and then additional 

tertiary physical-chemical treatment processes must be added. For this example, assume that 

conventional BNR and MF/RO processes will be used.

Based on a study of 50 BNR upgrade projects, the expected cost to upgrade a 10 mgd plant from 

secondary to AWT standards is on average about $82 million. Based on bid-data available from 

eleven wastewater treatment plants using MF-RO, adding MF-RO treatment to an existing water 

reclamation plant is estimated to cost between $54 million to $81 million depending on the 

concentrate disposal method. These costs could be significantly higher at existing sites because 

of site constraints. The total capital cost to upgrade a 10-mgd water reclamation facility not 

already meeting AWT limits could be in the range of $140 – $160 million, and operating costs 

would increase by at least $1.00 per thousand gallons treated (about $3.6 million per year), not 

including concentrate disposal costs which can range from an additional $1.10 per thousand 

gallons for a deep well up to $3.00 per thousand gallons for a brine concentrator system (these 

numbers have been normalized to reflect design flow and not concentrate flow). These additional

operating costs are in addition to the estimated $1.00 to $1.50 per thousand gallons being treated 

already being spent for typical Florida treatment facilities producing water for reuse. Table 3 

summarizes the incremental capital costs required to meet the proposed NNC. 
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Further, meeting low yearly average nutrient limits requires highly consistent performance by the 

treatment process, which will likely result in significant conservatism in the sizing of treatment 

facilities, provision of redundant systems, and other provisions to increase reliability that 

ultimately add additional costs. These additional costs are not accounted for in the estimates 

provided here. 

Table 3 Summary of Incremental Capital Costs ($M) for BNR and MF/RO 

Treatment to Upgrade a 10-mgd Water Reclamation Facility for Three 

Different Concentrate Disposal Options.

Deep Well 

(10,000 ft)3

Deep Well 

(2,500 ft)3

Zero Liquid 

Discharge4

BNR Upgrade 80 80 80

MF-RO Systems150 50 50

Concentrate Disposal211 4 31

Total 141 134 161

Notes:

1. Assumed recoveries: MF = 95%; RO = 85%.

2. Concentrate disposal costs are estimated from a combination of bid-data, vendor quotes, and a report published by the 

AWWA Membrane Residuals Management Subcommittee.

3. Excluding any pretreatment and standby disposal system.

4. With a brine concentrator and brine crystallizer; excluding cost for solids disposal; brine concentrator recovery assumed = 

95%.

The Big Picture

In order to further quantify the effect of the proposed NNC on the State, the case study variables 

described above were applied to all publicly owned wastewater treatment plants documented by 

FDEP. The plants were broken down into plants that already have AWT and ones that do not. 

AWT technology upgrades were assumed and projected to cost $8.20 per design gallon to 

upgrade. Subsequently, all plants would be required to be upgraded by the addition of an 

advanced tertiary technology following AWT. Reverse osmosis was assumed at an average cost 

of $5.00 per gallon per day of design treatment capacity. An additional cost of $1.10 per gallon 

of design treatment capacity was applied for concentrate disposal for facilities that have an 

existing deep injection well, as they were assumed to be able to construct an additional deep 

injection well for RO concentrate disposal. All other facilities included a $3.10 per gallon capital 

cost for a brine concentrator, as these facilities were assumed to not have access to a deep 

injection well. Lastly, the estimated increase in annual operating costs was calculated as follows: 

$1.00 per 1,000-gallons treated for AWT and MF/RO treatment, and $3.00 per 1,000 gallons for 

facilities that must treat RO concentrate with a brine concentrator. Applying the “dollar” per 

gallon unit capital costs to the FDEP database provided a lump sum capital expenditure for the 

state of $24.4 to $50.7 billion dollars. This cost was converted to an annual debt payment over an 
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assumed 30 years with 5% interest, which amounts $1.6 to $3.3 billion dollars plus an additional 

$0.4 to $1.3 billion dollars per year in increased operating costs. 

Much of the increase in operating costs can be attributed to power consumption. We anticipate 

that the addition of these facilities will increase overall power demand by almost 26 million 

megawatt-hours/year. The estimated increase in connected electrical load requires about 5 

percent of the total power generation capacity in Florida. Moreover, based on data published by 

the Department of Energy on CO2 emissions by power plants, the additional power consumption 

will increase CO2 emissions in Florida by over 17.4 million tons per year. 

These costs would be passed along to customers through increased wastewater rates. To estimate 

the increase in rates, facility upgrade costs and population information were used to calculate the 

average monthly cost per household. On average, rates would increase by an average of $673 to 

$726 per year per household.

Sample of Utilities

A sampling of utilities was conducted to support the general effort of analyzing the cost impacts 

to all of the Florida utilities described in the “Big Picture” approach. These utilities have based 

their estimated capital costs on various technical alternatives to meet the NNC rule that range 

from the addition of RO, to implementing 100% reuse via infrastructure improvements, to deep 

well injection of effluent for aquifer recharge. The utilities sampled have wastewater treatment 

facilities that range in size from 6 to 42 mgd, and are located in various areas of the state. Each 

utility reported their present average monthly residential customer wastewater charge and a 

preliminary estimate of the anticipated increase in rates to meet the proposed NNC. These 

percentages were translated to approximate rate increases. Table 4 summarizes the results of this 

analysis. The average rate increase reported across these 8 utilities ($618/yr) compares well with 

the independent conceptual statewide estimate prepared by the independent engineer 

($673/month to $726/month).
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Table 4 Summary of Estimated Capital Costs and Increases in Sewer Rates for 

Eight Florida Utilities to Construct Facilities to Meet Proposed Numeric 

Nutrient Criteria.

Capital Cost Yearly Sewer Rate Increase 

per Household

STATE OF FLORIDA1$24,400,000,000-

$50,700,000,0002

$673-$726

Bay County $42,000,000 $684.44

Broward County $425,000,000 $793.32

Destin Water $34,000,000 $581.16

Escambia County $275,000,000 $590.88

Hollywood $370,000,000 $995.88

Jacksonville $2,000,000,000 $815.04

Cross City3$5,800,000 $336.48

South Walton3$16,000,000 $147.00

Notes:

1. Estimated average costs for the State of Florida including annual O&M expenses and are shown for comparative 

purposes.

2. The low end of the range provides the probable opinion of cost assuming only plants with surface water discharges will 

be required to meet numeric nutrient criteria while the high end of the range assume that all plants will need to meet 

numeric nutrient criteria.

3. Assumes 2.5 persons per connection and 150 gpcd.

CONCLUSIONS

Implementation of the proposed numeric nutrient criteria will initiate widespread and dramatic 

changes in the way Florida wastewater utilities treat and reuse reclaimed water. The necessary

changes will likely require decades to fully implement. The major impacts expected for Florida 

consumers include the following:

1. Wastewater utility rates can be expected to at least double for those utilities required to meet 

the proposed NNC criteria. 

2. The total municipal wastewater treatment cost to the people of the State of Florida will range 

from $47.6 to $98.7 billion dollars over the next 30 years. The actual cost within this 

anticipated range will depend upon how many utilities would be required -- besides those 

discharging directly to surface water streams -- to meet these criteria.

3. Energy requirements for treatment could increase by almost 26 million megawatt-hours/year.

4. Emission of CO2 and other greenhouse gases could increase by over 17.4 million tons per 

year of CO2.