Everyone dumps into the sewage system, and, in this out-of-sight-out-of-mind society, doesn't give it another thought. We also blithely trust our drinking water to be safe, and that we can swim in our beautiful rivers. Most of us are oblivious to the processes that treat and neutralize our sewage and keep our drinking water safe. We only take notice when the system fails such as the floods that overwhelmed Ashland's sewage treatment plant last year, making their drinking water off limits for several weeks. An unknown industrial chemical release also knocked out a good portion of the local wastewater system plant last year, killing the bacteria used to process the sludge.

The Metropolitan Wastewater Management Commission [MWMC], which recently won the 1998 National Pretreatment Program Excellence Award, is currently reviewing standards for wastewater emissions for various industrial pollutants. The standards are set with four goals in mind:

The Commission is comparing current standards for meeting those goals with new standards just issued by the EPA. The focus is biosolids, treated sewage sludge, the end product of a lengthy treatment process. Solid material removed from wastewater is first treated by anaerobic digestion for about 30 days and then stored in lagoons for several years. After drying it becomes suitable as fertilizer and soil amendment. EPA standards are specifically set to insure that fertilizer from residual sewage biosolids do not contaminate plants; higher pollutant concentrations are illegal. However, European limits for many chemicals are anywhere from 10 to 50% lower than EPA's, and MWMC's recommendations have been to keep local biosolids quality cleaner than federal standards.

The Biosolids Citizen Advisory Committee appointed by MWMC to review options for expansion of the biosolids disposal program based its recommendations on the assumption that limits on concentrations of regulated metals should be 50% lower than EPA's maximum allowable limits, a standard supported by MWMC staff. The higher standards support the Commission's goal of minimizing environmental impact, while promoting pollution prevention rather than clean-up. It also ensures a high quality fertilizer product for farmers, and provides flexibility and an overall safety margin. Higher standards also eliminate onerous record-keeping requirements and the need for regulatory oversight.

The biosolids quality goal of 50% of EPA's standards, however, impacts the calculated local limits* of industrial pollutants, particularly for zinc. Zinc, an essential nutrient for plants and humans, is necessary in soil, but it's also a heavy metal that becomes toxic at certain levels. The local limit for zinc is 5.7 mg/l; if the recommended goal of 50% of EPA standards is used, the new limit would be about 1.5 mg/l.

Local industries are concerned that this lower limit on zinc will be difficult to meet with existing technology, and would necessitate expensive new equipment. They are also concerned that arrival of new zinc-using industries would force all companies to further decrease their emissions. The affected companies argue for using 100% of EPA's biosolids standards, claiming that industry is unfairly singled out for regulation, while residences and commercial establishments contribute the largest share of zinc to the system through the gradual deterioration of old plumbing. Residential and commercial emissions are expected to decline, however, as plumbing renovation becomes necessary in older buildings. PVC, the standard for new buildings for the last 20 years, has no known emissions and will be used for replacement.

To establish standards, maximum allowable limits of zinc received daily at the treatment plant have been established for each goal:

The lowest allowable limit, 42 lbs./day then becomes the standard. The amount of zinc released into the system by non-industrial sources is then subtracted, leaving the amount to be allocated to industries. This is then divided by the industrial flow, calculated at 780,000 gallons a day, including a safety factor, to figure the local limit for zinc. Only one local business, Gheen Irrigation Works, cannot meet the resulting limit.

In November, the Metro Wastewater Management Commission will hold a public hearing on zinc limits. Several alternatives will be discussed:

1. Raise the biosolids goal for zinc to 60%, making the local limit for zinc approximately 2.8mg/l, rather than 1.5mg/l. Leave the biosolids goal for the other metals at 50%.

2. Maintain 50% biosolids goal for all metals with the following options:

        a. zinc limit will be 1.5mg/l

b. two-tier system: 1.0 mg/l limit for new users; 3.0 mg/l for existing industries.

       c. 1.5mg/l limit with a compliance schedule for existing users         allowing, say, five years to meet the limit.

For further information, contact James Ollerenshaw, Technical Services Manager for the City of Eugene, 682-8600, james.ollerenshaw@ci.eugene.or.us.

* All numerical values are preliminary estimates that may change prior to the final calculation of limits.

Hen Cackles

©Wanda Ballentine, 1998