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Nitrogen Balance in a Pond System Receiving Tertiary Effluent
Author(s) -
Lund L. J.
Publication year - 1999
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1999.00472425002800040029x
Subject(s) - effluent , lysimeter , denitrification , environmental science , tin , hydrology (agriculture) , subsurface flow , environmental engineering , wetland , nitrate , surface water , constructed wetland , wastewater , nitrogen , sewage treatment , outflow , water quality , chemistry , soil water , ecology , geology , groundwater , soil science , geotechnical engineering , oceanography , organic chemistry , biology
A constructed wetland system near Riverside, CA, received tertiary treated effluent from the local wastewater treatment plant. This nitrate‐dominated effluent flowed through four ponds with a combined area of 10 ha, which were connected in series. Flow measuring devices were installed on the inlet and outlet to the pond system and suction lysimeters were installed beneath the ponds. Flow data, samples of surface water, and lysimeter extracts were collected for over 18 mo. Water and N balances were developed for a 1‐yr period, during which flow to the ponds was continuous. Of the water entering the pond system, 37% left as outflow, 3% evaporated, and 60% infiltrated. The average total inorganic nitrogen (TIN) concentration in the outflow was reduced by 32% compared with the inflow concentration (11.1 mg L −1 vs. 16.3 mg L −1 ). The average TIN concentration was 3.6 mg L −1 in extracts from beneath the ponds. Using a mass balance approach, 62% of the inflow TIN was not accounted for by TIN leaving the pond system in surface and subsurface flow. This TIN was lost from the system, most likely by denitrification. When expressed on an area basis, the TIN loss was approximately 1500 mg m −2 d −1 , a value typical for many effluent dominated wetlands. Based on the results of this study, the city of Riverside decided to expand and enhance the wetlands for use in meeting their N discharge requirements, rather than investing in major capital improvements in additional in‐plant treatment facilities.