9.3 Example of the Microcosm-WET Test
Examples of WET tests using a microcosm are presented below for sewage-treated
domestic and plant drainage water, rice-washed effluent, paddy field effluent, golf
course effluent, factory effluent, and landfill leachate.
9.3.1 Sewage-Treated Domestic Drainage
Sewage-treated water from domestic drainage that was suction filtered using a 1 μm
diameter membrane (ADVANTEC, GS-25) was added at the initial stage of microcosm cultivation (day 0), and the addition concentrations were set to 0% and 80% in
the microcosm medium. By comparing the 80% addition of the sewage-treated
domestic drainage with the control system (0% addition), the ecological effects
were assessed relative to the total toxicity. As a result, in the sewage-treated
domestic drainage, the extinction of Aeolosoma hemprichi was observed, whereas
the decreases observed in Lecane sp., Philodina erythrophthalma, Tolypothrix sp.,
and Scenedesmus quadricauda tended to recover. Even in the evaluation using P
and R, the initial P and R values tended to decrease in the sewage-treated domestic
drainage more than in the control system, and it can be inferred that respiration and
photosynthesis were inhibited. With respect to the classification patterns of ecosystem influence (i.e., maintenance, recovery, metastasis, and disintegration of the
system), the sewage-treated domestic drainage (80%) was classified as a metastasized system.
9.3.2 Sewage-Treated Plant Drainage
Sewage-treated water from plant drainage that was suction filtered using a 1 μm
diameter membrane (ADVANTEC, GS-25) was added at the initial stage of microcosm cultivation (day 0), and the addition concentrations were set to 0%, 20%, 40%,
and 80% in the microcosm medium. The ecological effects were evaluated from the
total toxicity by adding a dilution stage (0%, 20%, 40%, and 80%) of sewage-treated
plant drainage, which was highly toxic. As a result, at 80%, all micro-animals and
Tolypothrix sp. went extinct, and, at 40%, only Cyclidium glaucoma maintained its
abundance, while the abundance of Tolypothrix sp. decreased. At 20%, Aeolosoma
hemprichi became extinct, and the populations of other species, except for Chlorella
sp., decreased. Even in the evaluation using P and R, as shown in Fig. 9.5, P and R
transitions were similar to those in the control system, and the P/R ratio was
observed to gradually decline. From the results obtained when the sewage-treated
plant drainage was diluted in a stepwise manner, when the influence patterns were
9 Application to the Whole Effluent Toxicity Test
173
Examples of WET tests using a microcosm are presented below for sewage-treated
domestic and plant drainage water, rice-washed effluent, paddy field effluent, golf
course effluent, factory effluent, and landfill leachate.
9.3.1 Sewage-Treated Domestic Drainage
Sewage-treated water from domestic drainage that was suction filtered using a 1 μm
diameter membrane (ADVANTEC, GS-25) was added at the initial stage of microcosm cultivation (day 0), and the addition concentrations were set to 0% and 80% in
the microcosm medium. By comparing the 80% addition of the sewage-treated
domestic drainage with the control system (0% addition), the ecological effects
were assessed relative to the total toxicity. As a result, in the sewage-treated
domestic drainage, the extinction of Aeolosoma hemprichi was observed, whereas
the decreases observed in Lecane sp., Philodina erythrophthalma, Tolypothrix sp.,
and Scenedesmus quadricauda tended to recover. Even in the evaluation using P
and R, the initial P and R values tended to decrease in the sewage-treated domestic
drainage more than in the control system, and it can be inferred that respiration and
photosynthesis were inhibited. With respect to the classification patterns of ecosystem influence (i.e., maintenance, recovery, metastasis, and disintegration of the
system), the sewage-treated domestic drainage (80%) was classified as a metastasized system.
9.3.2 Sewage-Treated Plant Drainage
Sewage-treated water from plant drainage that was suction filtered using a 1 μm
diameter membrane (ADVANTEC, GS-25) was added at the initial stage of microcosm cultivation (day 0), and the addition concentrations were set to 0%, 20%, 40%,
and 80% in the microcosm medium. The ecological effects were evaluated from the
total toxicity by adding a dilution stage (0%, 20%, 40%, and 80%) of sewage-treated
plant drainage, which was highly toxic. As a result, at 80%, all micro-animals and
Tolypothrix sp. went extinct, and, at 40%, only Cyclidium glaucoma maintained its
abundance, while the abundance of Tolypothrix sp. decreased. At 20%, Aeolosoma
hemprichi became extinct, and the populations of other species, except for Chlorella
sp., decreased. Even in the evaluation using P and R, as shown in Fig. 9.5, P and R
transitions were similar to those in the control system, and the P/R ratio was
observed to gradually decline. From the results obtained when the sewage-treated
plant drainage was diluted in a stepwise manner, when the influence patterns were
9 Application to the Whole Effluent Toxicity Test
173