67    PRETREATMENT OF BLACK LIQUOR
SPILLS EFFLUENT
H.M. Poggi-Varaldo, P3 Consulting Engineer
Mexico D.F., 07300, Mexico
C. Estrada-Vazquez
Centre of Advanced Studies and Research (CINVESTAV)
Dept. Biotechnology and Bioengineering
Mexico City, Mexico
G. Fernandez-Villagomez
Centre for Disaster and Hazards Prevention (CENAPRED) and UNAM
Mexico City, Mexico
F. Esparza-Garcia
Centre of Advanced Studies and Research (CINVESTAV)
Dept. Biotechnology and Bioengineering
Mexico City, Mexico
INTRODUCTION
The Mexican pulp and paper industry (PPI) manufactures nearly 700,000 tonnes of pulp/yr and
2,900,000 tonnes of paper/year. Approximately half of the pulp production is made by the Kraft
process. Nearly 60% of the Kraft mills are nonintegrated factories, i.e., they manufacture non-
bleached pulp.' The PPI contributes with a 2.1% share of the industrial GIP and it directly employs 31,000 persons. The installed production capacity is distributed among 67 plants. They are
concentrated in the four main water basins of Mexico. The pulp production decreased 20% in the
last five years, reflecting the international and national recessions.2
The PPI discharges approximately 100 million m3/yr of wastewater, which represents ca. 12%
of the annual industrial discharges and the second position in the ranking of main water industrial polluters in Mexico.3 Currently, the PPI is facing more stringent standards for wastewater
discharges and associated permits. Also, environmental law enforcement is increasing its pressure over all the industrial sectors, PPI included. In the background, a trend to reach the more severe environmental criteria prevailing for the PPI in the NAFTA partners of Mexico is active.2
Water conservation, segregation, and reuse, together with process changes, are the first tools
for minimizing wastewater generation and lowering organic and toxic loads.3-4 However, the occasional or intentional spills and discharges of the industry still need to be treated.2
Application of anaerobic treatment to the forest-industry effluents has noticeably increased in
the last ten years. This technology, particularly the immobilized biomass reactors, offers clear
advantages over aerobic and phys-chem treatment processes.5-7 Among the advantages, we may
quote the following: low energy consumption, capability to treat warm wastewaters, biogas generation, compact design (high loading rate operation), minimal nutrient requirements, and low
amounts of waste sludge to dispose of.
Much research has been conducted on anaerobic treatment of the PPI wastwaters. Outstanding
advances have been made by Scandinavian, Dutch, and Mexican research teams in the last ten
years on the application of anaerobic proceses to a variety of PPI effluents.7-'9 One of the most
challenging issues has been the treatment of the wastewaters polluted by spent pulping liquors.
These effluents are quite toxic to aquatic fauna and microbes, and contain considerable amounts
of recalcitrant organic matter.6
51st Purdue Industrial Waste Conference Proceedings, 1996, Ann Arbor Press, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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