Power Station Effluent Research Articles

Field and Experimental Studies on the Effects of a power station effluent on tubificidae (Oligochaeta, Annelida)

1. Higher numbers of sexually mature worms of L. hoffmeisteri were found in the River Trent downstream from Drakelow Power Stations than upstream. 2. The condenser effluent from the power stations not only increased the temperature of the river but also produced a considerable increase in the concentration of dissolved oxygen. 3. Experiments were therefore carried out on the effects of these two variables on the reproductive rate of the worms. 4. In these experiments it was found that: (a) L. hoffmeisteri increased its rate of egg production with increase in temperature up to about 25°C while T. tubifex maintained a fairly steady rate of egg production over a range of temperatures from 10–25°C. (b) L. hoffmeisteri maintained a fairly steady rate of egg and cocoon production over a wide range of oxygen concentrations above 2 ppm. 5. Therefore it seems likely that the difference between the numbers of sexually mature L. hoffmeisteri upstream and downstream from the power station were influenced more by the increased temperature, than the increased oxygen levels of the power station effluent, though under extreme conditions of deoxygenation, aeration of the river by the cooling towers at the power stations could increase the abundance of this species.

The distribution, abundance and life-histories of stoneflies (Plecoptera) and mayflies (Ephemeroptera) in a British River, warmed by cooling-water from a power station

1. The River Severn at Ironbridge is warmed by cooling-water from Ironbridge “A” power station. Water temperatures over the years 1965–1967 were raised by values ranging from 0.5 to 7.2°C above ambient. 2. Collections of Plecoptera and Ephemeroptera were taken from three reaches in the vicinity of the cooling water discharge. “A” was situated 400 m upstream, “C” 800 m downstream and “E”, 2 km downstream of the outfalls. 3. The river at all three stations was fast flowing and normally fairly shallow with a stony substratum. 4. The water was alkaline with B.O.D. values of 0.9—5.0 ppm. There were no significant chemical changes from “A” to “E”. 5. Natural water temperatures varied from 0°C to 20.6°C. Downstream of the warm water outfalls the range was 0°C to 24.8°C. Mean weekly temperatures were raised by between 0.2°C to 4°C. There was no temperature stratification at the three sampling stations. 6. Thirteen species of Plecoptera and twenty-one species of Ephemeroptera were recorded. Ten species of Ephemeroptera (including three Caenis spp) constituted 95% of the total numbers collected. 7. Distribution of nymphs at “A”, “C” and “E” changed with river level and season. Species found commonly in the marginal grasses were those most active and common in invertebrate drift. 8. When compared with the faunas of other rivers and streams, the Severn at Ironbridge is a transitional area, with species common to hill streams and larger rivers. 9. The use of fine nets (24 meshes/cm) facilitated the more accurate determination of life-histories. 10. Life-histories of Taeniopteryx nebulosa, Ephemerella ignita, Heptagenia sulphurea, Baetis pumilus, Baetis bioculatus, Baetis rhodani, Baetis vernus and Baetis buceratus are described for both heated and unheated reaches. 11. Under natural conditions at “A”, three distinct types of life-history were defined among the eight species and the relationships between their life-histories and the natural temperature cycles differ. (a) T. nebulosa is a winter grower, nymphs only develop to maturity after September, though some were found in May and June at “A”. Temperature range for nymphs was approximately 17°C to 0°C. (b) E. ignita and B. bioculatus are both summer growers. Nymphs occur over a range of about 6.5°C to 22°C naturally. (c) The other species had more complex hatching, growth and emergence periods. H. sulphurea, B. rhodani, B. pumilus and B. buceratus nymphs grew quickly during February–May. Numbers were low in the height of summer and the controlling factor is probably competition for food and space with the “summer” species. 12. All species show a range of temperature tolerance during each life-history phase. This tolerance is considered to be a mechanism evolved to give the species some flexibility to withstand natural variations in climate from year to year. 13. E. ignitanymphs were larger and B. bioculatus better grown in May 1965 than in May 1966. This difference was probably related to the date on which 6°C was first reached and not to the time/temperature factor during the whole winter. 14. There was no really obvious “succession” of species in the Severn as found in small streams. 15. Effects of the power station effluent are considered from two aspects. There is some evidence that small, early hatched nymphs of Taeniopteryx were absent from “C” and “E” in June, but not from “A”. Later nymphs grew and hatched simultaneously at all three stations. There is no evidence of any other effects on the distribution and abundance of species. There may have been a small advance, of up to one week in the hatching times of Taeniopteryx and E. ignita in April 1967 but the data are not highly significant. The advances of 3–5 weeks in temperature shown by LANGFORD (1970) are not reflected in the life-histories of Plecoptera or Ephemeroptera. 16. All the evidence indicates that the heated effluent from Ironbridge “A” has no significant effects on the distribution and ecology of any of the eight species. Nymphs of some of the Ephemeroptera were collected over the whole range of river temperature, i.e. 0°C to 24.8°C, while the summer species were recorded over the whole summer range, i.e. 6°C to 24.8°C. T. nebulosa was restricted in its hatching and growth by temperatures over about 17°C both upstream and downstream of the power station. 17. It is suggested that the ability of each species to tolerate wide temperature range in different life-history stages is sufficient to enable the species to withstand and survive unnatural temperature conditions, provided that these temperatures are not sustained, or lethal to all stages, i.e. egg, nymph or adult. 18. Further studies on the long-term variations in life-histories in relation to river conditions are in progress.

Some changes in intertidal sand communities due to thermal pollution.

A very brief review is given of the way in which heated effluents can affect marine and estuarine environments. Some of the effects of the Hunterston Generating Station, Ayrshire, Scotland are described. This station discharges cooling seawater at about 10ºC above ambient at a rate of about 91000 m 3 /h. A prolonged ecological survey of the adjacent sandy beach for several years before and after the power station came into operation suggests that changes in the densities of the commonest organism, the bivalve Tellina tenuis , are not attributable to thermal effects. By contrast, the growth rates of young stages of Tellina appear to have increased. Breeding and growth at Hunterston of the intertidal sand-burrowing amphipod Urothoë brevicornis has been compared with a control population 3 km away, at Millport. Hunterston amphipods show an earlier breeding season and a more prolonged growth period compared with Millport animals. It is suggested that in open sea situations, in temperate waters, present power station effluents have relatively small effects. However, it should not be assumed that the increasing future disposals of waste heat will not have more drastic effects on the environment.

Contribution to the residence time of sulfur dioxide in a polluted atmosphere

The atmospheric oxidation of SO2 to SO4= has received much attention because of its importance in atmospheric pollution. In studies on the dispersion of effluents from stacks the oxidation or absorption of sulfur dioxide is of interest, since it shortens the residence time and leads to lower ground level concentrations. Previous measurements have shown that initially the oxidation is quite rapid (almost 30% in about 100 min) for humidities above 70%. In Frankfurt am Main the concentration of air pollutants, wind direction and speed, air temperature, and relative humidity have been continuously recorded for several years. In certain cases short-term peaks (5 to 15 min) of CO2 and SO2 concentrations can be defined as an influence of power station effluents. The CO2 and SO2 concentrations leaving the stack are well known. Carbon dioxide is almost inert, whereas the proportion of sulfur dioxide can decrease by oxidation or absorption while being transported through the atmosphere. In comparison with emissions the air quality measurements in Frankfurt am Main estimate an increased ratio of CO2 to SO2. That is a loss of almost 50% of the total sulfur content in a period of 20 min to 1 hour, depending on meteorological conditions.

The effect of temperature on the life cycle, growth and fecundity of Branchiura sowerbyi (Oligochaeta: Tubificidae)

Branchiura sowerbyi Beddard was probably introduced to Britain with exotic plants consigned to botanic gardens. The British populations occur mainly in artificially warmed habitats such as lily ponds in botanic gardens and power station effluents but a few are found at natural temperatures. Branchiura completed its life cycle in about a year both in the river Avon, Wiltshire, at natural temperatures and in the warm effluent from a power station discharging into the river Thames. In a worm culture maintained at natural temperatures the rate of cocoon production reached a peak in summer and was closely related to temperature.In the laboratory it was found that the optimum temperature for cocoon laying in mature worms, also growth in sexually immature worms, was near 25°C. The optimum temperature for growth in sexually mature worms, however, was lower (10°C in the Avon population and 15°C in the Thames population). It followed that at 20°–25°C the growth of sexually mature worms was probably depressed by the high rate of cocoon production.