Research on wetlands

7/29/2019 Research on wetlands

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In comparison with wastewater-treatment plants, a semi natural wetland involves low

construction and maintenance costs over the long term, does not consume non-renewable

energy, and does not produce sludge to be disposed.

Constructed wetlands are generally used for treating domestic wastewater, for improving

the quality of the water bodies, or as secondary and even tertiary treatment (Avsar and

others 2007). On the other hand, traditional wastewater-treatment systems are designed to

treat highly concentrated wastewaters: they remove pollutants from concentrated wastewater

more efficiently than wetland systems.For example, Italian government legislation suggests

the use of wetland systems to treat wastewater for urban agglomerates with less than 2000

inhabitants (e.g., D.L.vo n. 152 1999).

Traditional plants, like all other industrial plants, consume energy and produce waste

(Breaux and others 1995; Mitsch and Gosselink 2000; Viessman and Hammer 1998;

Tchobanoglous and Burton 1991). Natural systems can therefore represent a virtually

expense-free alternative to other technological wastewater-treatment processes (Breaux and

others 1995; Cardoch and others 2000; Ko and others 2004; Steer and others 2003).

The Experimental Treatment Wetland

The experimental domestic wastewater treatment plant will be built near the wastewater

source because conveyance of wastewater over a long distance is expensive and impractical.

The experimental domestic wastewater treatment plant is a VSB wetland. It will be

constructed at the back of the Female hostel (Iya lode Tinubu Hall) to verify the efficiency of

these system in the treatment of wastewater entering the treatment plant.

The water entering the system will come from a domestic channel and is expected to be

characterized by sewage, kitchen wastewater and laundry wastewater.

The wetland will be 50 m wide and 4.14 km long with a mean depth of 80 cm and will

divided into three treatment beds of differing vegetation.

The first treatment bed will be covered withPhragmites karka (commonly known as Reeds).

The second treatment bed will be covered with Vetiveria nigritana (the Nigerian specie of

Vetiver), and finally, the third treatment bed will be covered a combination of both

vegetation.

The components of the wastewater-treatment system will be determined starting from the

inflow sewage characteristics defined quantitatively, as per capita water supply and the

number of Equivalent Inhabitants (EI), and qualitatively, as the daily load of pollutants. The

wetland inflow and outflow rates being equal, the EI number (12,975) will be deduced from

the mean daily flow rate of the experimental wetland (2595 m3/day).

METHODS

Estimates of the daily loading rate of nitrogen (organic N, total ammonia-N, NO2--N, NO3

-

-N, and total N) and phosphorus (total P) to the demonstration wetland from the RWRF,

and daily export rate of these same nutrients from the wetland, will be calculated for

each week during the periods January 4, 1996 to March 31, 1998 (ConfigurationA) and February 18, 1999 to March 28, 2002 (Configuration B). These rates will be


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estimated by combining concentration data with total daily inflow and outflow volume data

obtained as follows. Each week, water samples will be collected from the inflow and

outflow pipelines and analysed within 24 hours of collection for total ammonia-N (NH3+,

NH4+)-N, hereafter referred to as TAN), total Kjeldahl nitrogen (TKN), nitrate-N (NO3--

N), and total P concentrations, according to standard methods (APHA, 1998).

Details of the individual laboratory analysis are presented in Smith et al. (2000) and in

Thullen et al., (2002). The concentration of organic N will be calculated as the difference

between TKN and TAN, and total N concentration will be calculated as the sum of TKN, and

NO3--N. Inflow to the demonstration wetland will be measured by means of a current meter

and outflow will be measured by a similar current meter. The meters will be read and reset

daily, providing a measurement of the total inflow and outflow volumes for the day on

which each set of water samples will be collected.

I will be measuring the nutrient-removal performance of the demonstration wetland in the

manner suggested for effluent-load removal efficiency (Reed et al. 1988, Kadlec and Knight

1996). Removal efficiency (RE) for a given N species or for total P is defined as the percent

by which the load of that particular constituent is reduced by the wetland:

RE = [(Li - Lo)/ Li] 100%

Where:

Li is the load imported from the female hostel

Lo is the load exported from the wetland, both in units of kg d-1.

RE calculated in this manner has a maximum value of 100% but no lower bound.


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References

American Public Health Association (APHA), American Water Works Association (AWWA)

and Water Environment Federation (WEF). (1998). Standard Methods for the Examination

of Water and Wastewater, 20th Edition. United Book Press, Inc., 6 Baltimore, Maryland.

Kadlec, R. H. and Knight, R. L. (1996). Treatment Wetlands. CRC Press, Boca Raton, FL,

USA.

Thullen, J. S., Sartoris, J. J. and W. E. Walton. (2002). Effects of vegetation management

in constructed wetland treatment cells on water quality and mosquito production. Ecological

Engineering 18:441457.

Smith, L. K., Sartoris, J. J., Thullen, J. S. and Andersen, D. C. (2000). Investigation of

denitrification rates in an ammonia-dominated constructed wastewater-treatment wetland.

Wetlands 20: 684696.

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Research on wetlands