Field Test Results for Nitrogen Removal by the Constructed Wetland Component of an Agricultural Water Recycling System

Constructed wetland technology is currently evolving into an acceptable, economically competitive alternative for many wastewater treatment applications. Although showing great promise for removing carbonaceous materials from wastewater, wetland systems have not been as successful at nitrification. This is primarily due to oxygen limitations. Nitrification does occur in conventional wetland treatment systems, but typically requires long hydraulic retention times. This paper describes a study that first evaluated the capability of subsurface flow constructed wetlands to treat a high strength seafood processor wastewater and then evaluated passive aeration configurations and effluent recirculation with respect to nitrogen treatment efficiency. The first stage of a 2-stage wetland treatment system exhibited a relatively short hydraulic retention time and was designed for BOD removal only. The second stage wetland employed an unsaturated inlet zone and effluent recirculation to enhance nitrification. Results indicate that organic loading, and thus BOD removal, in the first stage wetland is key to optimal nitrification. Passive aeration through an unsaturated inlet zone and recirculation achieved up to 65-70 per cent ammonia nitrogen removal at hydraulic retention times of about 3.5 days. Inlet zone configuration and effluent recirculation is shown to enhance the nitrogen removal capability of constructed wetland treatment systems.

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Removal of nitrogen from coal gasification wastewater by nitrosofication and denitrosofication

Water Science & Technology ◽

10.2166/wst.1998.0011 ◽

1998 ◽

Vol 38 (1) ◽

pp. 39-46 ◽

Cited By ~ 2

Author(s):

Junxin Liu ◽

Weiguang Li ◽

Xiuheng Wang ◽

Hongyuan Liu ◽

Baozhen Wang

Keyword(s):

Nitrogen Removal ◽

Coal Gasification ◽

Oxygen Demand ◽

Test Results ◽

New Process ◽

Scale Test ◽

Coal Gasification Wastewater ◽

Total Nitrogen Removal ◽

Biological Nitrogen ◽

Bench Scale Test

In this paper, a study of a new process with nitrosofication and denitrosofication for nitrogen removal from coal gasification wastewater is reported. In the process, fibrous carriers were packed in an anoxic tank and an aerobic tank for the attached growth of the denitrifying bacteria and Nitrobacter respectively, and the suspended growth activated sludge was used in an aerobic tank for the growth of Nitrosomonas. A bench scale test has been carried out on the process, and the test results showed that using the process, 25% of the oxygen demand and 40% of the carbon source demand can be saved, and the efficiency of total nitrogen removal can increase over 10% as compared with a traditional process for biological nitrogen removal.

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