Treatment of Municipal Effluent in the Coastal of

Dr. John W. Day1,2, Dr. Robert R. Lane1,2, Jason N. Day1,2, Joel Lindsey1 1Comite Resources, Inc., Zachary, LA 2Coastal Ecology Institute, LSU, Baton Rouge, LA Over the last 5,000 years, switching of the River channel formed the present day delta Over the last 5,000 years:

Delta lobes were nourished yearly by spring overbank flooding of the Mississippi & its distributaries

Welder 1959 During the last 100 years: Flood Control & Urbanization

Levees have been built on all major rivers, halting spring overbank flooding of the Mississippi & its distributaries

In addition, roads, , spoil banks & development have further isolated and impounded many wetlands These changes have hydrologically isolated many wetlands from spring flooding, creating nutrient poor systems from what were naturally nutrient rich Results of recent landscape changes • 1,700 square miles of wetlands lost by 2000 • Most of the remaining areas are sinking at 2 - 10 mm yr-1 – Excessive or permanent flooding – Decreased productivity – Lack of new seedling recruitment – Susceptibility to saltwater intrusion How can treated municipal effluent help LA’s degraded wetlands? Usually, secondarily treated municipal effluent is simply discharged into nearby rivers and streams, causing water quality problems.

When effluent is discharged into wetlands instead, vegetative productivity is stimulated, leading to increased organic matter production, deposition, and increases in vertical accretion.

In addition, the freshwater component creates a buffer to saltwater intrusion events, which are very prevalent in today’s coastal environment. Wetlands also reduce storm surge. There is a long history of wetland wastewater treatment

• Wetlands have been used to treat wastewater for centuries • Wetlands chemically, physically, and biologically remove pollutants, sediments and nutrients from water flowing through them • Using wetlands for tertiary treatment of municipal effluent is more energy- and cost-efficient than conventional treatment Primary Removal Mechanisms • physical settling and filtration • chemical precipitation and adsorption • biological metabolic processes resulting in eventual burial, storage in vegetation, and denitrification Rate of application must balance rate of decay & immobilization

Nutrient Loading Rate - one of the most important controls in wetland systems Nutrient Loading vs. % Nutrient Removal

N

In LA’s wetlands receiving treated municipal effluent, nutrient loading is kept below 15 and 3 for N & P, respectively, providing very high nutrient removal rates.

Richardson & Nichols ‘85 Municipalities using Wetland Wastewater Assimilation in LA

Red: currently active Orange: in development Gust Island Hammond Tchfuncta Estates Breaux Bridge Mandeville

Broussard St. Martinville Iberia Parish Luling St Bernard Franklin Thibodaux Amelia Thibodaux

Thibodaux • city of 17,000 people • Discharge 4-6 MGD • 231 ha forested Distribution wetland System • Loading: – N 3.1 g m-2 yr-1 Control – P 0.6 g m-2 yr-1 • Discharging since 1992

Receiving Wetlands Outlet City constructed a distribution system to disperse the effluent over the

Close up view of an effluent discharge pipe (4 mgd) Monitoring Results • 9 years of monitoring indicate effluent is processed by the wetland system, with no harmful effects to the soils or water of the swamp. • Nutrient Reduction: (Zhang et al. 2000) – Nitrate 100% – Total nitrogen 69% – Total phosphorus 70%

• Increases in leaf growth: -N (mg/L) 3 -2 -1

Stem: 228.0 vs. 829.1 g m yr NO Leaf: 165.4 vs. 141.3 g m-2 yr-1 Distance from pipe (m) Enhanced Accretion Accretion (mm)

Year (Rybczyk et al. 2002) Wetland Restoration at Thibodaux

1992

2003

2000 Savings to Communities

Thibodaux $1.5 million

Breaux Bridge $2.6 million

Mandeville $5 million THANK YOU Major savings

Estimated Total Annual Costs for City of Thibodaux Wastewater Management: Wetland and Sand Filtration Options

Inputs for Wetland Estimated Total Cost at Total Annual Cost at Systems Cost Present Value Present Value THIBODAUX Lifetime: 30 yrs Lifetime: 30 yrs

WETLAND SYSTEM Capital Costs $820,100 $820,100 Recurrent Costs $20,500/yr $210,609 Total Cost ------$1,030,709 $34,357/yr

SAND FILTRATION Capital Costs $1,143,000 $1,143,000 Recurrent Costs $46,900/yr $481,834 Total ------$1,624,834 $54,161/yr Breaux Bridge

Breaux • city of 6,000 people Bridge • Discharge 1 MGD Oxidation Pond • 1475 ha forested wetland Receiving • Loading: -2 -1 Wetlands – N 1.87 g m yr – P 0.94 g m-2 yr-1 • Discharging since 1950

Outlet Monitoring Results

• No harmful effects to the soils or water of the swamp

• Nutrient Reduction: – Nitrate 100% – Total nitrogen 80% – Total phosphorus 87% • Increases in tree stem & leaf growth: Stem: 1392.8 vs. 745.2 g m-2 yr-1 Leaf: 981.3 vs. 813.9 g m-2 yr-1 Long term increase in tree growth

Tree Ring Analysis Treatment/Control Ratio Treatment/Control

(Hesse 1994) Conclusions

Using wetlands is a cost-effective and proven method of tertiary treatment of municipal effluent. Wastewater effluent positively effects LA’s wetlands by: • Increasing vegetative productivity • Increasing organic matter deposition • Increasing wetland surface elevation, counteracting high regional Conclusions

The addition of nutrient rich secondarily treated wastewater to LA’s hydrologically isolated and subsiding wetlands should be viewed as not only an economic alternative to conventional wastewater treatment, but as an ecological restoration technique for the effected wetland HammondHammond (6.8(6.8 mgd)mgd) AmeliaAmelia (1(1 mgd)mgd)

Discharge flow through Ramos forested wetland Ramos forested wetland, into Lake Palourde

Existing Chlorine Contact Chamber

New Pumping Station

4" Lateral

6" Distribution Line Existing Oxidation Pond N MandevilleMandeville (1.9(1.9 mgd)mgd) St.St. Martinville Martinville (1.5(1.5 mgd)mgd) Broussard (1.5 mgd) Luling (2.2 mgd) St. Bernard (1.4 mgd)