Characterization and remediation of toxic metals in wastewater reuse for agricultural irrigation

Expanding agricultural water demand has led to the reuse of wastewaters for irrigation purposes. Left untreated, these reused wastewaters may contaminate agricultural land, plants, and thereby food products. Common contaminants include toxic metals, which are conservative within the soil-plant-water system. While conventional treatment of these waste streams is possible the treatment is resource intensive leaving it beyond the reach of many developing nations. Inventory of metals in the plant-soil-water system may reveal health exposure risks, or may suggest metal buildup is below levels of concern. Accurate inventory takes into account the chemical pool into which soil metals are bound, and thus resultant mobility within the soil system. Where reduced soil metal loadings are desirable, a variety of inexpensive sorbents have been suggested to remove toxic metals in place of activated carbon. While involved research efforts have evaluated the field of possible sorbents in great depth little comparative research has been done, and the methods utilized have eased laboratory distinctions at the cost of modifying the system from its native conditions. This research utilizes Tessier’s method of sequential extractions to inventory metals in different chemical pools (Tessier et al., 1979). A field of inexpensive and widely available sorbents, including sugarcane bagasse, ground rice husk, and sawdust, is compared against the conventional metal removal techniques of activated carbon sorption and gypsum pH modification for chemical precipitation. A large percentage of metals present are bound to the soil reducible fraction, which may be mobile due to repetitive anoxic conditions under flood irrigation practices. Metal concentrations were higher in fields irrigated with groundwater over contaminated surface waters, suggesting metal groundwater contamination is present. Overall, bagasse, rice husk, and sawdust performed similarly but well below the performance of the activated carbon standard. The results indicate possible treatment methods and materials for industrial wastewater that can be used for irrigation or used as supplemental irrigation in Indian conditions. Locally available low-cost materials show great promise to be used as metal removal media. Further investigation with small plots or field scales would be necessary to confirm the benefit of results found in this study to make a realistic impact on Indian agriculture.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Agricultural & Biological Engr

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2010

Author dc:creator

• Anderson, Stephen M.

Contributors dc:contributor

• Kalita, Prasanta K.

• heavy metals
• toxic metals
• irrigation
• wastewater reuse
• agriculture
• India

Statement dc:rights

• © 2010 Stephen Mathias Anderson

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/16209

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/16209