Project Title: Application of the Marshland Upwelling System (MUS) to Treat Domestic Wastewater in Sensitive Coastal Areas
Principal Investigator(s): Kelly A. Rusch, Ronald F. Malone.

Accomplishments
Scheduled Tasks and Progress
Task 3: Fabrication and installation of the MUS
Fabrication and construction of the MUS at the Moss Point site was completed by March 2001. The observation and injection wells were installed by hydraulic jetting, where high-pressure water was used to insert the well casing into the subsurface. The injection well was installed to a depth of 12.5 ft. The wells were constructed of schedule 40 PVC, with a _" diameter pipe surrounded by a 2" diameter casing. The bottom of each observation well contained a one-foot section of wellscreen surrounded by gravel to prevent clogging and to facilitate sample collection of the water immediately surrounding the well. Each well was equipped with its own neoprene tubing to prevent cross-contamination during sampling. The original plan was to install two injection wells with one serving as a back-up in case of system failure. However, current operation of the system relies on only one main well. Previous studies of the MUS at Port Fourchon, Louisiana, have shown limited pressure build-up at the point of injection at a depth of 15 ft. In addition, due to the close vicinity of the wells, it was decided that an additional injection well may disturb the natural compaction of the soil and create a conduit for wastewater to short-circuit to the surface.

A total of 24 observation wells were installed at depths of 5, 7.5, and 10 ft below ground surface (BGS). The wells were arranged radially from the point of injection.

Three sets of background wells at each corresponding depth were also installed. The wells were placed upstream from the MUS in areas not influenced by the wastewater plume.

Wastewater collection for the MUS is housed in two polyethylene holding tanks located at the rear of camps A and B. The smaller tank (55 gallons) serves as temporary wastewater storage for camp A and the nearby public restroom. This tank was buried approximately 1 ft BGS in order to ensure a gravity-fed, influent wastestream. Collected water from tank A is routed to the main holding tank (300 gallons) adjacent to camp B via a sump pump and buried PVC piping. The main holding tank also collects gravity-fed wastewater from camp B.

Wastewater is sent to the injection well from the main holding tank by a motorized injection pump controlled by a timer and float switch. The injection pump has a maximum delivery of 1.5 gpm. To adjust the injected flow rate to desired levels, a by-pass line was incorporated into the injection line which routes a portion of the flow back to the tank. A volumetric flow meter was installed to measure the cumulative volume of wastewater injected into the system. A pressure transducer and data logger were installed along the injection line in order to monitor changes in subsurface permeability within the injection zone.

Task 4: Determination of influent wastewater characteristics
Initialization of the MUS took place on June 15, 2001. To determine the influent water quality, samples were drawn from the main holding tank and analyzed for total kjeldahl nitrogen, total ammonia nitrogen, total suspended solids, volatile suspended solids, biochemical oxygen demand, total phosphorus, ortho-phosphate, fecal coliforms, nitrate, nitrite, pH, dissolved oxygen, and temperature.

All samples were stored on ice following collection and immediately transported to the Louisiana State University (LSU) Water Quality laboratory for analysis. Analyses were performed on filtered samples.

Task 5: Determination of hydraulic conductivity of the experimental area.
Migration of the injected wastewater is largely dictated by the characteristics of the natural soil matrix. The LSU cone penetrometer truck performed several ground penetrations to obtain a soil profile. Background hydraulic conductivities were determined on May 16, 2001 using the piezometer or slug test procedure outlined in Freeze and Cherry, 1979. The recovery of the well to the added slug of water was estimated based on the time required for the water level to drop approximately 2 ft. The mean hydraulic conductivities for the 10, 7.5, and 5-ft wells are 687.14, 361.94, and 918 gpd/ft2 respectively.

Task 6: Determination of baseline salinity levels in the experimental area.
Salinity levels were recorded on wells a total of six times to determine the background salinity levels. These levels were recorded using a refractometer. Wells were first evacuated, and the levels were then recorded.

Task 7: Determination of dispersion patterns of the freshwater plume.
A dye study (Rhodamine WT dye) was initiated on 7/11/01. The concentrate dye was diluted from 630mL to 19 L using tap water. The flowrate of the injection pump was 1.5 gal/min. The pump was scheduled to begin injecting every 3 hours for a period of thirty minutes. Dye levels in each well were recorded using a calibrated flourometer. For the first fifteen days, someone was continuously taking samples from each well. Samples were drawn every 4 hours beginning at 6:00am and ending at 10:00pm. Dye has shown up in each of the 4-10 foot monitoring wells (A10, B10, C10, and D10) that are closest to the injection well. Elevated levels of dye have also shown up in two of the four 7.5 foot monitoring wells (B7.5 and D7.5). The average vertical and horizontal velocities were calculated based on the distance traveled by the dye and the time it took for the dye to reach the wells. From the average vertical velocity, a worst case retention time was calculated. The retention time is 35 days if the dye is to travel straight up. This retention time would yield the least treatment of the wastewater.

Task 8: System evaluation.
We are currently collecting data at the first experimental regime, which is a flowrate of .5 gpm for thirty minutes every three hours. This data gives us the ability to draw a conclusion about what injection frequency and flowrate allows proper pressure dissipation within the subsurface. Once other flowrates have been evaluated, we will compare data to select the most efficient flow and injection frequency for the MUS system.

Task 9: Sample/data collection.
Salinity samples were collected on twelve different occasions. However, the first six events are considered background while the final five were collected after the system was in operation.

In-situ measurements were recorded for pH, Dissolved Oxygen, and temperature on seven occasions (3 background, 4 system was under operation). Samples were also refrigerated and transported to the LSU Water Quality Laboratory for analyses of nutrients, BOD5 (n=7), and fecal coliforms (n=3). The nutrient analyses included TKN (n=6), TAN (n=4), NO3 (n=7), NO2 (n=3), OP (n=4), and TP (n=6).

All wet chemistry analyses are being conducted in triplicate and in accordance with Standard Methods (APHA, 1998). Analyses are being conducted in the LSU Water Quality Laboratory. QA/QC protocols, in accordance with EPA guidelines, are established for each parameter analyzed.

Difficulties Encountered
While jetting the monitoring wells into the ground, we experienced some difficulties. In order to produce enough water pressure to dismantle the ground, we had to place a nozzle on the opening of the PVC pipe.

When the 55-gallon holding tank was first buried, the ground water pressure forced the tank out of the ground. As a solution, a concrete ring was formed around the tank to hold the tank in the ground.

We also encountered difficulties running nitrate analyses using the cadmium reduction method. There is an interfering compound in the samples. Samples have been submitted for ICP analysis to identify this interference.

Anticipated Success in Meeting Project Objectives in Scheduled Project Period

1. We expect to meet all of our project objectives with respect to laboratory studies during year one. Although we continue to have some difficulties with our field transplants, we envision completing the work during year two of this project. Modification of the Sea grass Model will be performed as part of a Master's thesis project under Richard Wetzel's direction. The project is currently under way, and we anticipate completion during year two of this project.

Preliminary Results
As of now, the MUS system is running properly and everything is on schedule.

Tasks and activities for next reporting period

Tasks and workplan for the next reporting period
Task 4: Determination of influent wastewater characteristics - This will continue with sampling

Task 8: System Evaluation - A number of flow rate/injection frequency treatments will be investigated to determine the best injection strategy.

Task 9: Sample/data collection

Task 10: Modeling plume movement - A laboratory-scale flume has been set-up at LSU to perform controlled studies. This data will be used in conjunction with field data to develop a transport model.

Task 12: Data analysis

Concerns or difficulties
None

Expenditures
Expenditures are in the range anticipated for work completed to date.