People living close to the plant in Monkton Lane, Farnham, have complained that the stench has recently got worse.
Thames Water, which manages the site, said emergency repair work could be the cause, but that it had written to residents to explain the situation.
Local councillor Roger Steel said he had been inundated with complaints, but the firm said it was not aware of any.
He said the Farnham Sewage Treatment Works was built 100 years ago and the odour problem was not new.
"In the summer residents are not able to open the windows when it's hot, children can't play in the garden.
"The odour gets into their clothes, even the wallpaper," Mr Steel said.
The councillor, who represents Farnham Moor Park on Waverley Borough Council, said the plant was too old to cope with the current population it served.
"There's plenty of room for them to perhaps rebuild a new plant or even to make major additions for it to be able to cope.
"It's been inadequate for years and years and years," he said.
In a statement, Thames Water said: "We're sorry if residents have noticed an increase in odour, but we're not aware of any complaints and [have] not noticed any difference.
"We sent a courtesy letter to inform residents we would be doing a piece of cleaning work, outside of day-to-day operations.
"Work stated last Tuesday, and is going well - we're ahead of schedule."

On Tuesday Mr Mugabe read a state-of-the-nation address he gave in August.
The error has been blamed on a mix-up in the president's office.
It took Vice-President Emmerson Mnangagwa two hours to submit the correct version because of demands from opposition MPs for an apology.
Wednesday's extraordinary session was called so that Mr Mugabe's speech could be officially recorded. The state-run Herald newspaper has printed the speech in full.
It says that the government plans to introduce legislation requiring senior public officials to declare assets as part of measures to tackle corruption.
The speech mix-up has prompted questions from the opposition over whether the president remains fit to lead, the BBC's Brian Hungwe reports from the capital, Harare.
After Mr Mugabe began speaking on Tuesday, it was not long before it dawned on those present that they had heard it all before, our reporter says.
When he delivered the speech last month on the economy, he was heckled by opposition MPs.
Analysis: Brian Hungwe, BBC Africa, Harare
This has been an unprecedented fiasco for Zimbabwe's 91-year-old leader. Never in his 35-year rule has he been allowed to be so publicly embarrassed.
He repeated the whole 27-minute speech at the opening of parliament, before military generals, judges, diplomats and both chambers of the house.
It has provoked a barrage of criticism. Some explain the mix-up as a sign of an internal power-struggle within the ruling Zanu-PF party - that he was deliberately given the wrong papers. Others see it as evidence that President Mugabe is too old to continue in the job. Sheer incompetence on the part of his office is another explanation.
Opposition MPs are unlikely to get the formal apology they demand. And for Zanu-PF, the debate over the effectiveness of Mr Mugabe's leadership style is unlikely to end.
The state broadcaster had cancelled its live feed of the opening of parliament on Tuesday fearing further disruptions.
Opposition MPs belonging to Movement for Democratic Change (MDC) reportedly kept quiet during the speech, as Zanu-PF supporters clapped at regular intervals.
However MDC spokesman Obert Gutu later told the Reuters news agency that it was "a historic blunder", adding: "Anyone who is still of a sound mind would have quickly picked it up that the speech was the wrong one."
Opposition MP Ruth Labode blamed infighting within the ruling Zanu-PF.
"I suspect someone did that deliberately to embarrass the old man," she told the BBC, saying a formal apology was necessary.
Mr Mugabe, who has been in power since 1980, is Africa's oldest leader.
Residents in a Surrey town have claimed their lives are being made a misery due to the smell from nearby sewage works.
[NEXT_CONCEPT]
Zimbabwe's vice-president has submitted to parliament a speech that President Robert Mugabe was supposed to deliver, a day after the 91-year-old leader accidentally gave the wrong one.