Sewage Restores Wetlands

Dr. Gary Shaffer, an environmental scientist at Southeastern Louisiana University, is working toward restoring Louisiana's wetlands...using sewage. Sewage from the city of Hammond is treated and then piped seven miles to an area known as 4-Mile Marsh. The sewage effluent is clean, but still high in nutrients such as phosphorus and nitrogen. The wastewater is released into the marsh where cypress trees, tupelo trees, grasses and other plants absorb the nutrients. Approximately one month after wastewater is released from the pipline, it leaves the marsh system cleaner than it used to leave the treatment plant.

The Hammond pipeline cost $7 million, but saves the city $2 million a year by eliminating the final stage of sewage treatment. 4 million gallons per day of sewage effluent are pumped into 4-Mile Marsh. The nutrients feed the wetland plants and the plants clean the water. It's a perfect symbiotic relationship.

Numerous experiments are being conducted at 4-Mile Marsh to determine the most effective techniques for restoring the coastal wetlands. Plant species, growth techniques and plant spacing are all being tested. EMIP® cypress trees were planted alongside bare root and container grown trees in the spring of 2007 and growth and survival rates were measured after the first growing season. EMIP® cypress trees out performed the bare root and container grown trees by leaps and bounds. EMIP® cypress trees had almost 100% survival and increased in basal diameter four times more than other trees. Some EMIP® trees grew so much that they became top heavy and fell over in the wet soils; however, the ones that were righted before nutria could eat the roots seem to be recovering well. EMIP delivered 600 additional cypress trees to 4-Mile Marsh this month to be used in experiments testing the most effective tree spacing for maximum nutrient absorption.

Sewage Effluent Released into 4-Mile Marsh