Project Title: A Low Cost Strategy for Treating and Reusing Wastewater on the Border

SCERP Project Number: W97-1

Principal Investigator: Larry Baker

Task Manager's affiliation: Arizona State University

Goal: The lack of adequate wastewater treatment facilities is a major problem for cities along the U.S.-Mexico border. In this study, the feasibility of linking "natural" treatment systems to treat and recharge wastewater in a pilot-scale treatment system for Nogales, Arizona, is explored. The system consists of an aerated lagoon, a wetland, and percolation ponds. Both river discharge and groundwater recharge options are being examined from the standpoint of water quality. The project goal is to evaluate a low-cost, low tech, treatment system to treat and reuse wastewater effluent and recharge it to the groundwater aquifer for later use.

The study site is Nogales, Arizona, where a lagoon treatment system exists. A pilot-scale wetland treatment system was proposed in a collaborative effort between the U.S. Bureau of Reclamation (BuRec) and the City of Nogales. ASU will build pilot-scale percolation basins using soils collected from three potential recharge sites to simulate groundwater recharge of treated effluent. This is the first lagoon-wetland-recharge system in the Southwest. ASU will analyze the performance of the entire treatment system with respect to water quality standards for effluent-dominated streams (lagoon/wetland system) and municipal drinking water (lagoon/wetland/recharge system). Practical design and operational criteria for wetland treatment systems and recharge basins will be assessed for arid border cities. Hydrologic and ecosystem impacts of several options for discharging or recharging effluent from the Nogales wastewater treatment plant are being explored. The project will benefit Nogales and other border cities that need low-cost, low technology, environmentally-sound alternatives for sewage treatment and sustainable water supplies. The following activities have been accomplished:

1) Design of the wetland treatment system;

2) Evaluation of the treatment performance of the existing lagoon system;

3) Started a series of laboratory experiments to examine water quality changes that occur during infiltration of Nogales wastewater through local soils;

4) Initiated an evaluation of the hydraulic characteristics of various wetland designs and started a "pre-pilot" study of a treatment wetland in Kingman, Arizona.

The FY96 SCERP-supported phase of this project: WQ96-1

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Last updated 10/30/00