The dairy company irrigated wastewater on eight nearby farms.

It owned three, Bruntwood, Buxton and Bardowie farms, which had no stock but were used as “cut and carry” operations, using the wastewater to grow grass crops for farmers.

The other five were “satellite farms” which it did not own, but the farms did receive wastewater for irrigation.

In total, the farms gave Fonterra 471 hectares to irrigate wastewater.

On average there was about 360kg of nitrogen per hectare, irrigated across the three farms it owned.

Grass growing as part of the cut and carry operation removed about 9 tonnes of dry matter per hectare, or about 240kg of nitrogen, leaving about 120kg surplus.

It’s the surplus nitrogen left in the land which had people worried about their drinking water.

Fonterra said the proposed wastewater plant would reduce nitrate leaching from the cut and carry farms by more than 50 per cent.

The factory’s site manager Jonathan Bouda and its environmental manager Alice Rackham outlined details of the wastewater plant and efforts to meet with the community during a recent visit.

They were aware of a Hautapu community group which opposed building the plant next to the factory because of concerns around noise and odour pollution.

The group said while the factory had been a good neighbour for many years, residential development from Cambridge was now creeping further out towards industry at Hautapu.

Rackham had presented to community meetings, showing how much the new wastewater plant would reduce nitrogen levels on the three irrigation farms.

She said the company was using engineering and environmental specialist Pattle Delamore Partners [PDP] to design a modern treatment plant.

Fonterra had also been reviewing other wastewater plants around the world, including one in Ireland which operated in the middle of a town.

Rackham said the new plant would be designed to process low and medium strength wastewater, to be irrigated to land, except where there was heavy rainfall and the land may be too wet for irrigation.

In that case it will be discharged to river under strict conditions. Currently, all low strength wastewater is discharged to river.

High strength wastewater, typically high in solids and organic load, would continue to be spread to land by DairyFert, a Fonterra subsidiary.

Bouda had also attended community meetings and said the concerns about odour from a wastewater plant built at Hautapu did not come as a surprise.

“We were expecting some feedback and do recognise that some of our neighbours will have concerns.

“That’s why we have engaged with them now to take their concerns on-board as we work through the design phase of the new plant.”