From cesspits to sewers: a tale of wastewater treatment

The post on the history of pollution in the Manawatu River has been one of the most popular posts on this website. This post adds to that story with a history of Palmerston North’s sometimes beleaguered sewerage system.

In the 1870s, the early years of the township, there was no sewage network. Instead, households had “long-drops”, while hotels and boarding houses built cesspits to bury “nightsoil”. By 1877, the odour from these was becoming unbearable in some locations, and in 1879, the borough council prohibited the digging of open cesspits, instead creating a ten acre “sanitary reserve” for the burial of nightsoil and household refuse.

However, this too was the source of offensive smells and it was not long before the council was forced to consider a longer term solution – a sewage system.

The first earthenware sewer pipes were laid in 1890, and untreated sewage flowed from the Square along Fitzherbert Avenue and through the Esplanade to discharge into the river about 800 metres downstream from the Fitzherbert bridge. Though there were complaints (as outlined in the previous post on the Manawatu River) from towns and settlements downstream, there was no move to treat the sewage until the Department of Public Health intervened, following a bubonic plague scare in 1900, and insisted on treatment before discharge.

By 1905, sewage was treated using a series of septic tanks and filter beds, located on the bank of the river near Maxwell’s Line. Initially, the sewage was discharged directly to the Manawatu River, but later, diverted to the Mangaone Stream, which subsequently fed into the Manawatu River near the end of Shirriffs Road. At the time, the septic tanks were described as being the largest and most efficient in New Zealand. But by 1930, when Palmerston North had grown to a city, they had become hopelessly inadequate. Some improvements were made to the system, but even so, by the 1950s, when concern about the pollution of the river had heightened, the system was considered to be seriously overloaded. The city’s chief engineer instigated an investigation into the level of the pollution of the Manawatu River, which would then determine when a new system would have to be put in place. His conclusion was that “the self-purification capacity of the river is very high”, thereby justifying a considerable lag-time before work on a new treatment plant would be commenced. When in 1968, the new treatment plant was opened, it met the standards for discharge set by the Pollution Advisory Council, established under the Water Pollution Act 1953.

In 1985, aerated lagoons were developed to provide secondary treatment. However, the city’s sewerage troubles were not over – in times of high rainfall, the infiltration of stormwater into the system sometimes resulted in untreated sewage being forced up through manholes on to the city streets. The city council’s solution to this was an emergency by-pass which would discharge sewerage directly into the river.

Regional councils were established in 1989, and were charged with environmental management responsibilities under the Resource Management Act [see: A short history of regional government in NZ]. The regional council’s concern was that while the city’s sewage discharges met the Pollution Advisory Council standard, they did not meet all contact recreation standards (e.g., to safely swim). The city council on the other hand claimed that nutrient run-off from farms was also a major source of pollution in the region. This became a source of considerable tension between the two councils: with the regional council determined to lower the level of nutrients (especially phosphorus) in the river, and the city council resistant on the basis of cost. In the end, the city council’s consent to discharge sewage was to expire in 2006, and the council recognised that it would have to improve its treatment process in order to secure a new consent. The council consulted on several treatment options, included land-based options, but in the end decided on a river discharge option which included ultra-violet disinfection and phosphorous removal, and a wetland “land passage” leading to the outfall. The plant, located near the transfer station site off Maxwell’s Line, became fully operational by 2008 [see photo above].

Sources: A history of wastewater in Palmerston North, available from Palmerston North City Council website; “An uneasy relationship: Palmerston North City and the Manawatu River 1941 – 2006” (2007), Masters Thesis by Jill White; Palmerston North City Council.

Photo top: Workmen laying sewer pipes (c 1905), by Samuel Jickell. This 18 inch sewer was laid on a ferro concrete support as the land was swamp 14 foot deep. Samuel Jickell, also the photographer, was Borough Engineer for the Palmerston North Borough Council 1904-1919. Bottom: Current wastewater treatment plant (Palmerston North City Council).

See also: Manawatu River – pollutions concerns date back to 1890 ; A short history of regional government in NZ

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