Analysis of Ammonia Toxicity in Landfill Leachates

Takuya Osada,Ryo Shoji,Keisuke Nemoto,Masato Yamada,Ayumi Hatano,Tomohiro Naruoka,Hiroki Nakanishi

doi:10.5402/2011/954626

Abstract

Toxicity identification evaluation (TIE) phase I manipulations and toxicity test with D. magna were conducted on leachates from an industrial waste landfill site in Japan. Physicochemical analysis detected heavy metals at concentrations insufficient to account for the observed acute toxicity. The graduated pH and aeration manipulations identified the prominent toxicity of ammonia. Based on joint toxicity with additive effects of unionized ammonia and ammonium ions, the unionized ammonia toxicity (LC50,NH3(aq)) was calculated as 3.3 ppm, and the toxicity of ammonium ions (LC50,NH4+) was calculated as 222 ppm. Then, the contribution of ammonia toxicity in the landfill leachate toxicity was calculated as 58.7 vol% of the total toxicity in the landfill leachate. Other specific toxicants masked by ammonia's toxicity were detected. Contribution rate of the toxicants other than by ammonia was 41.3 vol% of the total toxicity of the landfill leachate.

Highlights

Landfill leachates are highly polluted effluents [1]
Physico-chemical analysis data with LC50 value in each components were compared for chemical-specific Toxicity identification evaluation (TIE) approach, the results showed that heavy metals were not toxicity causative chemicals
A methodology to decide toxicity causative chemicals in landfill leachate based on the toxicity contribution rate and the effect of ammonia toxicity changing by pH was developed in this study

Summary

Introduction

Landfill leachates are highly polluted effluents [1]. The leachate has to be treated in a downstream waste water treatment plant, and it is necessary to identify toxicity causative chemicals for the effective treatment. Treatability-based TIE is a general approach in TIE to determine the effective water treatments and (if possible) thereby speculate the toxicity-controlling chemical(s). The approach is to compare chemical analysis data with concentration of chemicals to express toxicity (e.g., LC50, EC50 (the lethal or effective concentration for 50% of test organisms), etc.). In the chemicalspecific TIE, when concentration of many chemicals were higher than LC50 or EC50, toxicity causative chemicals for effective treatment cannot be identified. Contribution rate approach for identification of toxicity causative chemicals can consider the effect of pH in landfill leachate toxicity for more effective treatment

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Conclusion