1-STEP® filter: the solution for cost-effective removal of phosphorous and other priority chemicals from WWTP effluent

Kramer, J.F.1, Menkveld, H.W.H.2, Bechger, M.3, Cunliffe, T.2, Nieuwenhuijzen, A.F. van1

1 Witteveen+Bos Consulting Engineers, NL, 2 Nijhuis Industries UK and Ireland, UK, 3 Waternet, NL



To ensure a cleaner and protected environment and human health conditions for the future, both UK and EU environmental legislation require further improvement of surface water quality by advanced wastewater treatment.  Ultra-low phosphorous standards (< 0.25 mg P/L) altogether with low nitrogen and total suspended solids standards are on the way.  As a consequence, additional treatment and extension of wastewater treatment plants (WWTPs) by tertiary treatment becomes necessary.  The 1-STEP® filter is a compact, cost-effective, efficient and effective total tertiary treatment solution, developed and successfully implemented in the Netherlands over the last decade.  This paper presents the results of full operation over five years (2012-2017) of the 1-STEP® filter at WWTP Horstermeer of Waternet, Amsterdam.  The 1-STEP® filter combines four distinct processes in one filter unit: (1) coagulation and flocculation of phosphorous and suspended solids, (2) denitrification of nitrate, (3) filtration of flocs and particles (4) adsorption of micro pollutants.


Advanced Phosphorous removal, Advanced Nitrogen removal, Micro pollutant removal, Priority chemicals removal, total effluent polishing, 1-STEP® filter, Biological activated carbon filtration



Authorities responsible for the quality of surface and groundwater have increasing attention for improving effluents from wastewater treatment plants (WWTPs).  This directly results from the implementation of the European Union’s Water Framework Directive (WFD) in 2000.  The WFD requires that good ecological and chemical conditions for both surface and groundwater are achieved in 2015.  Part of the WFD is a list of substances that have to be dealt with in high priority with regard to the impact on the water quality.  To deal with these substances, the removal of these substances (partly from WWTP effluent) should be increased.  It is emphasized here that the water quality requirements mentioned in WFD are only related to surface water and not directly to WWTP effluent.

The WFD and UK legislations focus on a few different groups of substances, of which nutrients (N and P), suspended solids, organic micro pollutants and priority chemicals are some prominent examples. For the UK especially a standard of 0.25 mg P/L is expected, at this time considered as an ultra-low phosphorous standard.  Studies have shown that the common activated sludge systems are unable to remove these substances sufficiently to newly required low levels.  At the moment, a few technologies are available that effectively and consistently produce WFD compliant effluents, but only a limited number of these technologies cost-effectively deals with all relevant substances in one compact total tertiary treatment solution.  The 1-STEP® filter is an advanced example of these technologies.

Water and Wastewater Companies in England and Wales are at present implementing the capital expenditures according to the performance commitments over the various AMP6 plans, to meet their existing commitments and targets for customers, the regulators and stakeholders.  Meanwhile, the methodology for the 2019 price review (PR19) is about to be finalised.  Further quality enhancement schemes might be included as performance commitments in the “new-to-be-developed” AMP7 plans for 2020-25, requiring a significant improvement on the 2015-20 levels of performance.  This due to more stringent standards, amongst others for Phosphorous, but also to comply with the upcoming Water Industry National Environment Programme (WINEP) currently being drafted by Environment Agency and a final version expected by March 2018.  Results from the ongoing Chemical Investigation Programme 2 with demonstration trials and pilot studies will be included in the PR19 submission of Water and Wastewater Companies to Ofwat.  The initial findings of the trial plants show there is no ´Magic Bullet´ that is effective on all problem substances so far. The 1-STEP® filter might be an effective solution for various problem substances, as demonstrated at WWTP Horstermeer of Waternet in the Netherlands.

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