All technology has benefits and disbenefits. An example is the widespread use of chlorine in pollution control work and in particular in preventing the spread of pathogens. Its benefits are patent. Its disbenefits are that it is a virulent poison and is manufactured, delivered and used at some risk to those employed in this work and to some extent to the public. Train spills well illustrate that the same applies to many other chemicals.
In the case of sewage treatment the benefit depends on the circumstances and there are probably no benefits to the environment by treating the sewage that now goes down the long outfalls, as has already been explained. However, the disbenefits remain, leaving a substantial negative environmental impact.
Firstly, for many years there has been a debate as to whether the best way to control pollution is to concentrate the wastes or to disperse them widely. Land-based treatment concentrates them in a sludge. There is a long history of technology to overcome the adverse impact of such sludges in our environment. The selection of the best technology is one of the main tasks facing engineers who design plants. The problems can be overcome but the potential for pollution always remains. The cost of applying appropriate technology is a major factor in the cost of any plant. As theory and practice have shown that there is no problem in disposal by dispersion through long outfalls, this factor becomes a major adverse impact of treatment. Dispersion is a safer environmental option than concentration in our case.
Secondly, the long outfalls use no power, whereas treatment plants of the size contemplated use a significnat amount of power (it is practical for a plant serving much bigger populations to generate electricity. Power is not then needed; there may even be sufficient to leave a net power gain).
Thirdly, the construcion of sewers, sewage works and the like carries hazards. Statistically, some seventy of the workers on a one hundred million dollar project of this nature will suffer sufficient injury to receive compensation from The Workmen's Compensation Board. The statistics show that one or two will be permanentlhy impaired. Some hazard also will continue throughout the life of the plant. Such human costs are taken for granted where works are necessary but are inexcusable where they are not.
Fourthly, the effluent from a treatment plant cannot be discharged without chlorination except through a long outfall because other forms of treatment do not adequately destroy pathogens. One either produces a more toxic waste or, if a long outfall were still employed, one pays for the construction and operation of a facility that achieves nothing that the outfall alone was not achieving - a fatuous situation.
Fifthly there is the permanent land impact damage. No one wants a sewage treatment plant near them, even if it is operated perfectly all the time. Even minor facilities that appear to have no physical impact will lower land values, as the recent instatllation of a pumping station has shown. In practice, all facilities that depend on human operatives and the availability of power go wrong on occasion. They may then smell. Also the sludge that the plant generates must be trucked out and the comings and goings of a major plant have all the attributes of a small industry. The existence of a plant has impacts far beyond its boundaries.
Sixthly, on the rare occasions when the plant goes wrong it may not produce the purified effluent for which it was designed. That is never the case with the long outfall which protects the environment with complete reliablity and with no use of power or risk of smell.
Lastly there is an adverse impact that is not environmental. It is the one raised by Dr. Littlepage. What will the electorate think when they find that the building of a plant has not enabled a single 'pollution' sign to be removed? And what will some later generation that has better scientific education think if they discover that this generation threw one hundred million dollars down the drain whilst at the same time doing little about pressing environmental and social problems?