NITROGEN ACCUMULATION IN A CONSTRUCTED WETLAND FOR DAIRY WASTEWATER TREATMENT¹

Abstract

: A free water surface (FWS) constructed wetland was installed at a dairy in Glendale, Arizona, to study the potential of such a wetland to remove nitrogen (N) from wastewater. The study objectives were: (1) to determine N removal from the wastewater, and (2) to evaluate N accumulation in soil and plant tissues. The system consisted of eight cells (70 × 9 × 1.5 m) planted with Typha domingensis, Scirpus validus, and Phragmites australis. The four cells in series were lined with plastic, and the four cells in a parallel series were lined with clay. Cells received approximately 180 m3/d of partially treated dairy effluent. Plant tissues and soil samples were collected above and below ground from 24 locations during one year. Total N removal from wastewater was about 17 percent. Clay‐lined cells accumulated more N in the soil and less N in plant biomass compared with plastic lined cells. Plant biomass accounted for approximately 60 percent of total N accumulated in cells with dense plant communities. Ninety percent of accumulated soil N was organic. Total N accumulated in soil reached a maximum (1,100 mg/kg) eight months after the introduction of wastewater.

Performance of Tropical Vertical Subsurface Flow Constructed Wetlands at Different Hydraulic Loading Rates

“…Moreover, it is worth noting that an average pH value of 7.1 ± 0.4 and DO concentration of 4.2 ± 2.1 mg L −1 in the influent are favorable for effective nitrification. According to Shamir , the optimum pH for nitrification is between 7.2 and 9.0, and nitrification rate decreases significantly below pH 6. Also, Shamir reported that DO concentrations between 0.3 and 2 mg L −1 are the threshold values for effective nitrification.…”

“…According to Shamir , the optimum pH for nitrification is between 7.2 and 9.0, and nitrification rate decreases significantly below pH 6. Also, Shamir reported that DO concentrations between 0.3 and 2 mg L −1 are the threshold values for effective nitrification. Influent DO concentrations in this study were well above these suggested values.…”

Land Disposal of Centrate from Biosolids Production

“…High-ammonia nitrogen water sources include animal feed lot slurries (Ham, 2002), and centrate from biosolids processing (Jeavons et al, 1998). These sources can contain up to 1000 mg/l ammonia nitrogen and may be discharged into artificially established riparian (Hubbard et al, 1998) and wetland (Samir et al, 2001) receiving systems. Clarke and Baldwin (2002) tested the ammonia nitrogen tolerance of four emergent wetland species at levels of 0-400 mg/l ammonia-N under flooded and nonflooded conditions.…”

“…Toxicity may actually be due to release of ammonia gas into the water, as un-ionized ammonia was inhibitory to growth of rice and duckweed in aquatic systems at less than 10 mg/l (Wang, 1991). As long as the ammonia nitrogen concentration is kept below toxic levels, wetland and riparian plants can be used to remove nitrogen from effluent water (Hubbard et al, 1998;Samir et al, 2001). Hence, it is important to determine the critical levels of ammonia nitrogen for growth and toxicity to candidate species in constructed receiving systems, such as wetlands or buffer strips.…”

Carbon and nitrogen dynamics and greenhouse gases emissions in constructed wetlands: a review

“…The soil in CWs has been proved to be a major sink for N. However, although data on the influent and effluent N concentrations are often explicitly available; data on the N accumulation (DON, TN, NH 4 + or NO 3 − -N) within the soil profile of various CWs are scarce. Shamir et al (2001) measured 30-40 % N accumulation in soil of the total accumulated N in a clay-lined surface flow CWs system of which about 80 % of the total N accumulated was organic and the remainder was NH 4 + . The N accumulation decreased with soil depth, with 42-48 % in the upper 0.15 m and 20-24 % in deeper layers.…”