Whanganui business Tasman Tanning is in a two-year, $2 million battle to reduce the chromium in its wastewater and comply with a Whanganui District Council maximum.
Council requires its wastewater to have no more than 5mg of chromium per litre, or less than 10kg of chromium a day.
Until that level is reached, the dried sludge from Whanganui's Wastewater Treatment Plant will have to be expensively landfilled.
Present storage is cheap - in an unused pond at the plant site in Airport Rd. That space will, however, run out in three to four years, council infrastructure manager Mark Hughes said.
After that, depending on how much Tasman can reduce its chromium, the sludge may be suitable for application to land or even sale as a fertiliser.
Or, it may have to be expensively trucked to a Waikato landfill.
Tasman Tanning uses chromium to tan hides and make leather. There are other ways to make leather, but using chromium is the quickest and best, CEO Neville Dyer said.
The company is closing in on the 5mg/litre goal but not there yet, technical manager Craig Thiele said. One recent measurement had chromium at 5.8mg/litre.
It has reduced the chromium content of its wastewater by 80 per cent over the past six months. But it needed to go further, Hughes said.
The company is committed to doing that.
"We are working with council to achieve those numbers. They want to be able to dispose to land. We are aiming to try to reach that. We don't think we will reach zero but we are aiming to enable them to do that," Thiele said.
The problem has been "fugitive" discharges, from sources such as hides dripping fluid into general waste.
Chromium is an element and small amounts of chromium III are needed in the human body. But more than 5mg/litre in wastewater, when concentrated in dried sludge from the wastewater treatment plant, turns the sludge into a waste that has to be landfilled.
Chromium III can be converted to carcinogenic chromium VI by boiling or sun drying.
"We don't use any chromium VI at all, but we do have to be careful that none is generated anywhere from the chromium III," Thiele said.
It's going to take more money and time and a factory rethink for Tasman to reduce its chromium waste further.
The company bought a $1.8 million chromium extraction plant that has been working constantly since late last year. It has had "teething problems".
The aim was to extract chromium and reuse it in the tanning process, which would have saved money. But the chromium extracted needed further treatment before it could be reused. Treating it makes the operation cost-neutral rather than saving money.
The company's wastewater is monitored by council 24/7, but Tasman has bought its own lab equipment to do its own monitoring and get quicker access to the results.
The continuing effort to reduce chromium waste fits with Tasman's membership in the international Leather Working Group (LWG). The group aims to make tanning, a polluting industry when old technology is used, more environmentally sustainable.
The LWG has an audit process of 18 sections. Tasman is an audited member and aims for silver medal status, Dyer said.
Meeting environmental standards is now a big driver of the business and most staff are on board. The company's energy use, waste reduction and working conditions are all scrutinised.
It contributes about 25 per cent of the solids to Whanganui Wastewater Treatment Plant and wants to convert more of them into product. Some parts are already used in sausage casings. Others could be composted in future.
Tasman Tanning has about 200 staff and processes about 800,000 cattle hides a year. Half of these are packed into containers and exported semi-processed.
The rest are bought by the company and processed to finished leather.
"We are the only ones left in Australasia doing that," Dyer said.