subsequently decided to build one based on Granqvist’s proposal.^936 Aalto was clearly
unconvinced about the solution, as he asked as late as August 1931 for a statement from
the Voima- ja polttoainetaloudellinen yhdistys (Energy and Fuel Economy Associa-
tion) on the type of water treatment system that would best serve the sanatorium. Only
this statement provided a clear analysis of the problem and its solution.
According to the statement, popular dual cesspits were outdated. They were only able to
separate the majority of solid waste, but at the same time contaminated the water flowing
through the tank, as decomposition processes always take place in the tank. Although the
tanks had developed in previous years, they were only feasible for small quantities of water
and there was not sufficient empirical evidence of their use. The City of Turku had septic
tanks in use, in which only the waste water from lavatories was treated. Waste water from
sinks, washbasins, bathrooms and laundry rooms was not treated and bypassed the treat-
ment unit via a separate system. All buildings in Turku that had flushing lavatories had
two separate wastewater systems: one for the lavatories and one for all other wastewater.^937
Since the sanatorium’s sewage water system and flushing lavatories were largely com-
pleted, with the waste water from lavatories and washbasins directed to the same system,
introducing the septic tank system was difficult at this stage of a project. The treatment
plant would have needed to be rescaled and it would have become very large and expen-
sive to build. Voima- ja polttoainetaloudellinen yhdistys maintained in its report that
both the cesspit and septic tank systems were unsuitable for Paimio Sanatorium. The
only remaining option was the biological treatment plant, which was originally developed
for treating large quantities of waste water, such as those from entire town districts and
cities. Based on the positive experiences gained, the system had been used in hospitals,
sanatoria and army barracks. It was further stated in the report that the water flowing
through the biological treatment plant was adequately purified for release into an open
ditch without adverse environmental impact, as had been the plan for Paimio Sanatorium.
Moreover, the waste water from lavatories could be directed through the same pipes
as other waste water, and the biological treatment plant would process all waste water.
Voima- ja polttoainetaloudellinen yhdistys therefore recommended the use of a biological
wastewater treatment system.^938 The selected supplier was Yleinen Insinööritoimisto Oy
(General Engineering Office), which delivered the Danish-made biological treatment
system including machinery, and carried out the installation.^939
Since the project group had been unable to take into account the operating principles
of and spatial requirements for wastewater treatment at a sufficiently early stage, the project
group was left with no alternative solution. The expertise of the City of Turku waterworks
did not benefit the decision-making on the wastewater system for Paimio Sanatorium,
despite the fact that the City had been involved in the project with a one-third holding
936 Building Committee July 27, 1931, Section 1. PSA.
937 The letter and statement of the Voima- ja Polttoainetaloudellinen yhdistys, September 3, 1931. Documents related
to the Paimio Sanatorium project. AAM.
938 Ibidem.
939 Building Committee October 24, 1932, Section 1. PSA.