A shortage of HGV drivers is putting pressure on the supply chain for chemicals used to treat wastewater in the UK. As a result, the government has told wastewater treatment works in England they may be able to discharge effluent that has not been fully treated if needed.

Trade body Water UK has identified some disruption to the distribution of ferric sulfate to a small number of water companies. It’s used to remove phosphorus from wastewater. A Water UK spokesperson noted that the problem is a national shortage of specialist HGV drivers able to move the chemical and they do not expect the situation to improve in the short-term. They also stress that the shortage is not affecting drinking water treatment.

The Chemical Business Association, which represents the UK chemicals supply chain, found that 96% of its members are now experiencing issues with UK haulage, up from 63% in its last survey in June. It warned the government back in June that driver shortages would affect the supply of critical chemicals for the water and agriculture industry.

‘The supply chain situation in the UK is deteriorating,’ says Tim Doggett, the CBA’s chief executive. ‘We believe the impact of driver shortages is likely to get worse before it gets better.’ The chemical industry is likely to be worse hit than other sectors, he adds, because of the requirement for additional qualifications for drivers carrying hazardous substances.

Normally, wastewater treatment works need a permit to discharge treated effluent to surface water or groundwater. Permits contain conditions that control the quality of the discharged effluent. The Environment Agency for England has said that if wastewater treatment works can’t get hold of the necessary chemicals to meet the conditions of their permit they can still discharge effluent. This would only apply if the reasons they can’t obtain chemicals include the UK’s new relationship with the EU, the pandemic or other unavoidable supply chain failures.

According to a government spokesperson, the action is a time-limited, precautionary measure and there are ‘robust conditions’ in place to mitigate risks to the environment. ‘The most sensitive and high-risk watercourses will not be affected and any company planning to make use of this short-term measure must first agree its use with the Environment Agency, which will be checking compliance.’ No companies have yet to apply.

Short-term risks low

Ferric sulfate is used to remove phosphorus from wastewater in order to reduce the nutrients discharged into waterways. It’s usually the third stage of sewage treatment after biological processing which removes solids and organic matter.

‘There is potential for an increase in phosphorus levels at some isolated wastewater treatment works,’ says a Water UK spokesperson. ‘However, the [waiver] does not apply to wastewater treatment works that are likely to have a high environmental or downstream abstraction impact.’

‘The objective of tertiary treatment is to remove residual contaminants, specifically phosphorus, which is efficiently precipitated with ferric salts and can be separated from the wastewater by settling or flotation,’ explains Mårten Krogerus, a technology specialist in water treatment at the Finnish consultancy Afry. ‘If ferric sulfate or any other ferric/ferrous salt is not available, the third stage of treatment cannot be operated properly. Consequently, the wastewater discharged will contain higher concentrations of phosphorus but also organic matter and nitrogen.’

Increased loads of phosphorus will over time cause eutrophication and algal growth, says Krogerus. ‘However, the impact risk for short-term ferric sulfate shortages is considered relatively low, but long-term shortages may have more serious consequences.’

Other ferric or ferrous salts such as ferric chloride or ferrous sulfate may be used instead. Alternatives such as alum and polyaluminium chloride are also possible, although they are more expensive, says Krogerus. However, supply challenges are likely to be the same for them.

Ana Soares, professor of biotechnology engineering at Cranfield University, UK, says she was surprised to hear the announcement from the Environment Agency, which is known for its strict approach to environmental protection. However, she believes the agency will prioritise discharges and protect ‘sensitive’ rivers, for example where environmental quality is low, or agricultural run-off is high. ‘The water industry in this country is very reliant on chemicals for phosphorus removal. Perhaps this will encourage it to look at other technologies and not rely so completely on chemicals. European countries use a range of approaches such as biological nutrient removal but here only Severn Trent Water use bio-based removal processes.’

Currently, Water UK has not identified any supply issues for other chemicals. Krogerus says the availability of other key wastewater treatment chemicals, such as urea and phosphoric acid, are crucial for good performance of biological treatment plants and sludge dewatering. Lack of these chemicals would ‘relatively quickly’ lead to poor performance and elevated concentrations in the final wastewater discharge, especially without tertiary treatment. ‘This [English] development is concerning and, in addition to consequences for production, it may lead to non-compliance with given consents for discharge. Potentially it could result in penalties, limitations in industrial production or even longer shutdown periods for industrial activities.’

Correction: The name of Severn Trent Water was updated on 15 September 2021.