DTU Environment

Revurdering af person ækvivalent for fosfor

Anne Lørup Arildsen og Luca Vezzaro

Opgørelse af fosforindholdet i dansk husholdningsspildevand i årene

fra 1990 til 2017

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Hvem er vi?

• Anne Lørup Arildsen

• Forskningsassistent (arbejder nu hos

HOFOR)

• Har gjort størstedelen af arbejdet

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• Luca Vezzaro

• Lektor i modellering af urbane vandsystemer

(særlig fokus om vandkvalitet)

migRegnbetingedeudløb (live)

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Outline

• Formålet af projekt

• Metoden og datagrundlag

• Resultater

• Konklusioner og anbefalinger

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Objective of the project

• Phosphorous (P) reference value

(P/Person Equivalent)

– Expressed as kgP/PE/yr

• Used to estimate P loads from different

point source. For example:

– Diffuse, low density settlements

(spredt bebyggelse)

– WWTP discharges (if no direct

measurements are available)

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Distribution of P load from different point sources in 2017 (source:

Miljøstyrelsen, 2019)

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Objective of the project

• P reference value estimated back in 1990

• New legislation on P content in detergents

– EU regulation 648/2004 and 259/2012

– Valid from 2013 (laundry) and 2017 (dishwashers)

• Measurements from WWTP inlets in different countries

show a decrease in P concentrations

• What is the current P/PE in Denmark?

• What was the temporal evolution of the P load

throughout the last decades?

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Daily P/PE load for different WWTP in Gotheborg (Tumlin & Mattson,

2013)

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Methodologyprocedure for each plant

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New reference

value for P/PE Measured data

Sorting of

data

Analysis of

data

distribution

Data

validation

and outlier

removal

Calculation

of annual

reference

value

Repeated across all

the available years

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Data background

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• P load per Person Equivalent

• Data should only represent domestic

wastewater (no industrial contribution)

• Data from 56 wastewater treatment

plants were used

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Measurement distributions

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• Analysis of previous monitoring campaigns suggest that concentrations/loads are log-normally

distributed

Phosphorous BOD5

Cumulative density Cumulative density

We looked at the median value (not average value)

Assumption

confirmed

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Data validation

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• Outliers were removed based on the estimated

log-normal distributions

conc Log(conc)

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Calculation of annual P reference

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• BOD5 reference value: 60 gBOD5/PE/d

• For each measurement

𝑷𝒓𝒆𝒇,𝒊 =(𝑪𝑷,𝒊 ∙ 𝟔𝟎 𝒈𝑩𝑶𝑫𝟓

/𝒅)

𝑪𝑩𝑶𝑫𝟓,𝒊

• Yearly value (median of the year)

• If less than 3 measurements in a year, no value

was estimated

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ResultsAmount of available data

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• Duration of timeseries changed depending of the

plant Full data series (1990-2017) for 39

plants

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ResultsAmount of available data

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• Number of available

data changed from year

to year

More uncertain value

(based only on 3-5 samples)

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Temporal evolution of P loadPlant dependency

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• Three main patterns have been observed in the

plants Constant decrease

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Temporal evolution of P loadPlant dependency

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• Three main patterns have been observed in the

plants Initial increase, and then decrease

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Temporal evolution of P loadPlant dependency

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• Three main patterns have been observed in the

plants Sharp fall after 2006-7

Not possible to categorize the observed pattern according to

the plant characteristics

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Temporal evolution of P loadOverview over all the 56 plants

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Great variations

among plants

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Temporal evolution of P loadOverview over all the 56 plants

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Same figure as before –

only median value

New regulation on

detergents

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What about the big plants?Comparison with data from main Danish WWTP

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Effect of industrial

contribution on

estimation of PE

Similar trend

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Conclusions & Recommendations

• The annual P load per person equivalent has fallen by 34% in the last decade

• The reference value has fallen from 1-1.1 kgP/PE/yr (1990-2005) to 0,72 kgP/PE/yr

(2017)

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• Source control (regulation of P in

detergent) looks effective

• There is the need for a continous

analysis of existing data and re-

estimation of yearly P discharges

?

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Tak for opmærksomhed!

• Kontakt:

luve@env.dtu.dk

• Rapporten kan downloades på:

www.orbit.dtu.dk

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