A BIOLOGICAL AND CHEMICAL CHARACTERIZATION STRATEGY FOR SMALL AND MEDIUM-SIZED INDUSTRIES CONNECTED TO MUNICIPAL SEWAGE-TREATMENT PLANTS

A cost-effective strategy for the characterization of wastewater from small and medium-sized industries is described. A mobile laboratory, e quipped for performing on-site biological tests, was established near wastewater treatment facilities in two cities in Sweden for 1 week eac h in November 1992 and November 1993. The biological and chemical char acterization was done on 24-h samples from 29 industries representing 12 types of activity with a bias toward the surface treatment and grap hics industries. The biological testing program included a modified ni trification test, the Microtox(R) test, and a modified growth inhibiti on test using Selenastrum capricornutum (an alga test). A Ceriodaphnia dubia (crustacean) test was also used for some industries. Different chemical assessments, aimed at indicating toxic, persistent, and bioac cumulating substances, were chosen for each industry on the basis of i nformation they provided. Results show that sampling period and time a re important factors to consider when designing a characterization str ategy. Twenty-four-hour sampling is preferred to weekly sampling becau se highly toxic emissions of short duration that are detrimental to th e biological treatment plant may occur. Variability in emissions was s hown in this study but would not have been detected by a study based o n weekly sampling. The strategy developed in this study was shown to b e both a cost-effective and efficient tool for characterizing effluent s from small and medium-sized industries.