Washwater cake disposal and risks

2026.03.24

3.8   Deputy K.L. Moore of St. Mary , St. Ouen and St. Peter of the Minister for Infrastructure

regarding washwater cake material (OQ.45/2026):

Will the Minister state where washwater cake material is currently disposed of and whether it is applied to land during, or following, its disposal; and what assessment, if any, has been made of the associated risks linked to its disposal?

Connétable A.N. Jehan of St. John (The Minister for Infrastructure):

I thank the Deputy for her question. The sewage treatment works produces around 7,000 cubic metres of biosolids each year. Around ½ f this is incinerated through the energy recovery facility, while the other ½ is spread to agricultural land as fertiliser. Biosolids are analysed regularly for potentially toxic elements and nutrient value, the results of which are used to inform the risk of each individual piece of land's use, proposed cropping plan and other soil requirements. This use of biosolids reduces the reliance on imported chemical fertilisers.

1. Deputy K.L. Moore :

I believe the Minister missed out the part of the question asked what assessment has been made to the associated risks, and in asking him to do so I would like him to speak to the known concentration levels of 93 milligrams per kilo of P.F.A.S. in those in that wastewater cake.

The Connétable of St. John :

I thought I had addressed that in terms of looking at the nutrient balance of results and the individual pieces of land. I am pleased to say that an intervention that was agreed through the P.F.A.S. Steering Group was to stop the disposal of groundwater from boreholes at the airport fire training ground to the Island's foul sewer network. Since pumping ceased, monitoring shows that P.F.A.S. loading in the sewage treatment work system has reduced by two-thirds. Results also show a corresponding reduction in P.F.A.S. concentrations in the enhanced treated biosolids produced at Bellozanne. This matters because reductions in biosolids P.F.A.S. concentrations support current handling decisions for the management of the output from the sewage treatment works.

2. Deputy J. Renouf of St. Brelade :

I think the Minister edged towards an answer to the question I wanted to ask there, but could he confirm, therefore, that P.F.A.S. concentrations in that biosolid waste are routinely measured before material is spread on fields, so that it can be tailored to the known concentrations of individual fields?

The Connétable of St. John :

I am not sure of the Deputy 's definition of "routinely". I am aware that there is frequent testing that is carried out, and we have seen significant improvements in those testing results. I should say that the testing has shown there is no indication that produce from outside the airport fire training ground P.F.A.S. hotspot have been affected more than global background levels.

3. Deputy K.L. Moore :

Have any concerns been raised with the Minister regarding the incineration of this waste at the Energy from Waste plant?

The Connétable of St. John :

No, in short. It is not something that I have been made aware of, but I am happy to go away and check if we have had any feedback