Most stories start with once upon a time, ours do the same,

Dr. Down, Chemist of the Massachusetts State Board of Health, after a series of experiments concluded with confidence that rigorous agitation of air does not contribute to sewage purification. Maaon and Hine asserted aeration had negligible effect on sewage treatment. Fowler in 1897, recorded, aeration results in "no tangible oxidation". Indeed It was the time when literature and investigations suggested that aeration of sewage as per se is not a viable adjunct in wastewater treatment.

Though there were some hopes and advances in using aeration in some form or the another as,

For instance, Black and Phelps in order to deal with pollution in New York harbour, performed experiments with raw and partially septicized sewage and convinced that at certain conditions, aerating the sewage can remove readily degradable organic matter.

While, Clark and Gage suggested that aeration can be used as primary treatment before filtration. They found that aeration of sewage for 24 hours reduced the free and albuminoid nitrogen to some extent. Use of aerated sewage with green growth, Protococcus and Scenetesmus, contributed to significant nitrification within 24 hours.

Still there was nothing solid when it comes to aeration of sewage.

The moment of observation

Dr. Fowler after his visit to the prestigious Lawrence Experiment Station, Massachusetts, in November 1912, mentioned about observing strands of algae growth in the bottle in which sewage was aerated. And upon suggestion by Dr. Fowler that "research can be conducted on these lines", series of experiments were performed by Ardern and Lockett, which changes the course of how wastewater treatment was performed forever.

 What I felt great about reading this paper?

 Preliminary experiments -  5 weeks to 24 hours

80 oz. Manchester sewage samples were taken and aerated until complete nitrification occurred. Ordinary filter pumps were used for aerating the sewage.

First complete nitrification of the sample took 5 weeks time (It's astounding that for my bioreactor it took the same time to observe significant nitrification).

After the settlement of formed solids, the clear influent was decanted, and raw sewage was reintroduced. The process continued, and it was discovered that the amount of solids deposited increased with time. Interestingly, the time required for complete nitrification decreased as a result, and the complete nitrification was happening within 24 hours.

In the impossibility of searching a different term, the accumulated solids were named as "activated sludge".

The striking observations from the preliminary experiments were

1. Alkalinity is a crucial requirement and they even added small quantity of external alkali to perform nitrification reaction. They recognized that alkalinity is required to neutralize the nitric acid produced during the nitrification reaction.

(When I was doing my master thesis with aerobic granular sludge, I was performing nitrification experiment without adding sufficient alkali, and the consequence was nitrification was extremely erratic and I came back from lab wondering what went wrong. I came back and read Metcalf & eddy and realized that I was not adding sufficient alkali. Next time, I was doing it in the right way and the experiment went well. So, I can say with confidence from my personal experience that reading ancient papers can be helpful for amateur researchers at least and it's a way of acknowledging their contribution, and a way of remembering them).

 2. Intimate contact between activated sludge and sewage is important (The paper had tables to prove this point, I'm not sharing that here).

The paper had observations made from a series of experiments, for instance, the effect of temperature, maintenance of sludge activity, so on and so-forth which I'm not adding it here and the reader can refer if to the original article as the link is embedded.

One question remains, what scientists and engineers at that time felt after reading/knowing this paper by Ardern and Lockett?

The discussions part in the paper answers the question, it was interesting to read but hard to summarize, so I again leave it to the readers to go through that part.

https://onlinelibrary.wiley.com/doi/abs/10.1002/jctb.5000331005