GENERAL MOTORS DE MEXICO (GMM) RAMOS ARIZPE AUTOMOTIVE COMPLEX (RAAC ATER CONSERVATION AND REUSE PROGRAM Supporting material Ramos Arizpe, Coahuila, MEXICO February 26, 2001 0228/01
GENERAL MOTORS DE MEXICO (GMM) RAMOS ARIZPE AUTOMOTIVE COMPLEX(RAAC) WATER CONSERVATION AND REUSE PROGRAM 1. INTRODUCTION General Motors de Mexico(GMM) Ramos Arizpe Automotive Complex(RAAC) is located in an arid region in the State of Coahuila. in northeast Mexico. Complex operations began in 1980. In 2000. RAAC manufactured 590.000 engines, 171,000 transmissions, and assembled 222,000 passenger vehicles The only source of water in the area where the Complex is located is a small, semi-confined aquifer, that has a limited water storage capacity, and a relatively high salt content (approximately 2000 mg/l total dissolved solids). This does not allow direct well-water use for industrial or domestic purposes. So it becomes necessary for GM to treat well water, and this is accomplished by utilizing several reverse osmosis(RO)desalination units When the Complex began operations, the following systems were installed: 1)several RO units for well water desalting, and an ion-exchange system to polish portions of the water supply, 2)separate physical-chemical wastewater treatment systems for the assembly and engine plant effluents, and 3)a biological wastewater treatment system for sanitary waste Since 1986, several things have occurred that changed RAAC's approach to water management. These include: 1)well-water levels have decreased, 2) fees that must be paid to the National Water Commission(CNA)for water rights have substantially increased, 3)CNA imposed limits on well water withdrawal, 4)limits on the concentrations of several parameters in the waste streams were issued, 5) The demand for high quality water has increased, due to the expansion of the Complex. The main consequences of these events are that all wastewater must be treated, and water reuse is practically the only source of supply for additional water requirements. The reduced well water withdrawal will eventually allow for an increased To reduce water consumption, and to reduce the pollution load to the environment, the following main programs have been undertaken: 1)the development of a continuous intensive water conservation program, that includes leak detection and repair, and review of the different water-treatment and water-using processes to detect water-saving opportunities; 2)the lementation of an innovative system to recover most of the by-product brine from the RO Solid os:3)the construction of solar evaporation ponds to convert the final brine stream to salts for potential reuse; 4)the implementation of a complete physical-chemical and biological wastewater treatment facility, to treat all industrial and sanitary wastewater; 5)the implementation of an innovative system to recover about 70% of the secondary effluent that good quality treated sanitary wastewater to irrigate RAAC gardens and sport-fields, and,o results from the biological treatment of pre-treated industrial wastewater; and 6)the reuse create a man-made lagoon, that is the center of a recreational area for the Complex workers
and their families Fig. I presents the main components and flow diagram of RAAC Water Management System The six main programs that have been implemented to reduce well water withdrawal and ollution impact to the environment are also indicated in the diagram WELL WATER sporanox委 Bracke DOMESTIC USERS Concentra Revers Osmosis oa/ to industrial ad Evap。 ration Fig 1- General Motors de Mexico Ramos Arizpe Automotive Complex Water Management System, indicating the six main programs that have been implemented to reduce well water withdrawal and pollution impact to the environment The following paragraphs present a brief description of these programs, and their main accomplishments from the point of view of water conservation and recovery, and pollution control 1. WATER CONSERVATION PROGRAM This includes leak detection and repair, and review of the different water-treatment and water using processes to detect water-saving opportunities The main actions that have been implemented to satisfy water-use reduction objectives include 0228/0 3/10
Water treatment: Increase of the well water reverse osmosis recovery from 67 to 73% October, 1998) Industrial use: Reuse of non-treated effluent streams with low contaminant load in processes that do not require high quality water; control of air-supply houses and cooling tower blow-down; control of the phosphate line water discharges by monitoring conductivity or other relevant indicators; Domestic use: Installation of water-saving devices at showers and toilets, and of reduced-discharge "water-closets The effect of the water-conservation activities that were undertaken in the period 1986-1997 are reflected in the decrease in well-water withdrawal that is observed for this period in Fig. 2 For the period 1997-2000, the effect of water-conservation activities is relatively minor in comparison to the reuse projects that have been undertaken, due to the fact the actions with the largest effect were implemented during the first years of the program Fig. 2. -Variation of RAAC well water withdrawal 2. RECOVERY OF WELL WATER TREATMENT BY-PRODUCT STREAM During the period 1980-1997, RAAC well water reverse osmosis systems operated at 67%6 recovery. This means that 33 of the well water flow was discharged to a nearby creek as a concentrated by-product stream. An innovative system was implemented in 1997 to recover about 80% of this brine stream. Other saline effluents, including the ion exchange resin regeneration waste and sand- filter backwash, are also treated in this system The brine treatment/recovery system comprises the following main processes: 1)softening, 2) microfiltration, and 3)reverse osmosis. A filter-press is used for dehydrating the softening by product stream. Fig 3 presents a flow diagram of RAAC brine-recovery system(BRS) 0228/01
Fig 3 - FLOW DIAGRAM OF THE BRINE RECOVERY SYSTEM INSTALLED AT GM DE MEXICO RAMOS ARIZPE COMPLEX Well water RO BRINE COLLECTION REACTION TANK BRINE R.O. ORATON SALTS TO CONCENTRATE SOLAR EVAPORATION The BRS has been operating almost continuously for about 3 V years now. It has produced a permeate(product water) with low salt content, that has been used mainly for the engine and transmission plants'water supply. It has also allowed RAAC to substantially reduce well-water withdrawal. The successful operation of the BRS has allowed RAAC to increase significantly the percentage of utilization of waters with high salt content(from 67-73 to 94.6% overall recovery), as indicated below Before implementation of BRS After implementation of BRS Well water, Well water Usable water well water Well wate Usable w (100%) (67-73%)(100%) By-product By-product (27%) (33-27%) RO 5.4% The main environmental benefits obtained from the bRs have been to reduce well water withdrawal, and to extend the aquifer life