Comparison of technological treatment options

Middlesex University, Danish Technical University, University of Ljubljana, ENVICAT, Anjou Recherche.

ScorePP Dissemination Workshop(2-3 February 2010)

To address the technologies available for eliminating the discharge of priority pollutants to receiving waters as a result of different activities and to carry out a comparative analysis to assess the most appropriate and feasible reduction technologies

Overall objectives

• Stormwater BMPs

• Greywater treatment and reuse systems for household

wastewater

• Industrial wastewater treatment

• Municipal wastewater treatments

• Sludge disposal

• Assessment of the feasibility of the different treatment

options for PPs

Treatment options considered in ScorePP

Stormwater Best Management Practices

• Stormwater control systems close to the source

• Control water quantity & quality

• Provide social amenity

• Infiltration/detention followed by discharge at a controlled rate

• Used individually, in a treatment train or in combination with conventional piped systems

Stormwater BMPs

• Structural and non-structural

• Constructed wetlands• Detention basin• Retention pond• Lagoon• Green roof• Settlement tank• Filter strips• Swales• Infiltration basins • Soakaways• Porous asphalt • Porous paving

Fundamental unit

Physical processes Chemical processes Biological processes

Pollutant behaviour: Susceptibility of a particular pollutant to the identified processes

Adsorption, Settling, Filtration, Volatilisation

BMP characteristics which influence removal processes:dry & wet area/volumes; retention & drain down times; surface exposure times; hydraulic/flow attenuation; vegetative, algal & microbial components; presence of sorption sites/nature and pore sizes of substrate; existence of aerobic/anaerobic conditions

Flocculation, Precipitation, Photolysis

Plant/algal uptake, Microbial degradation

Identification of the potential pollutant removal efficiency within a specific BMP

Order of preference for the use of BMPs to remove Pb and Benzo (a) pyrene

Comparison of theoretical ranking with measured data: Organic PPs in SSF CW

Priority pollutant Matamoros et al., (2007) Score PP methodology

Removal efficiency (%)

Ranked data Ranked data

Pentachlorobenzene >99 2 1

Endosulphan >99 2 2.5

Lindane >99 2 5

Pentachlorophenol 94 4 2.5

Chlorpyrifos 83 5 4

Alachlor 80 6 7

Simazine 25 7 6

Diuron 0 8 8

• In the absence of field data, enables end-users to evaluate BMPs from the perspective of the removal of non-standard pollutants of concern; demonstrates critical discrimination across BMPs although infiltration basins and sub-surface flow constructed wetlands consistently rank most highly for the removal of priority pollutants

• BMP order of preference for the removal of PPs compares well with field data available to date but more field data required to refine and calibrate this approach

• Provides input to development of emission control strategies (e.g. ScorePP)

• Does not take into consideration the suitability of different options for specific geographical locations, e.g. potential for groundwater contamination due to infiltration in unsuitable soil type.

Summary of the ability of stormwater BMPs to remove PPs

Household Greywater Treatment and Reuse Systems

• GREYWATER = BATHROOM (sinks, baths and showers) KITCHEN (sinks, dishwashers) LAUNDRY (sinks, washing machines) NO TOILET WASTE

• Previous research has concentrated on conventional water quality monitoring parameters (e.g. BOD, TSS, nutrients, and pathogens).

• Increasing support for decentralised WWT – increasing pressures on water supplies, improved potential for recycling, water savings etc.

• Difficult to draw conclusions about the efficiency of the various treatment options (individually or in a train) for PS/PHS in greywater

– The majority of removal efficiency studies relate to treatment of combined wastewater

– Greywater treatment is highly site-specific, wide range of treatment trains, many still in development or pilot stage

– Lack of data on micropollutant treatment efficiency. Only 1 greywater study reporting both inlet and outlet concentrations of PS/PHS.

Household greywater

Priority substance properties

Priority substance

sources

GreywaterPre-treatment

systems

Recyclingsystems

Water savings

Cost-benefit analysis

Nutrient recycling

Priority substance presence

Priority substanceconcentrations/

loads

Removal efficiencies

Operationalrisks

Health risksconnections

Risks to theenvironment

Electricity consumption

Chemical consumption

Operational costs

Installation costs

InformationInformation reviewed

A6

A2 A3 A4

Primary settling tank Sand-filter

UV-filter Service water tank

A0

A1 A5

Multi-stage Rotating Biological Contactor

Secondary settling tank

A7

RBC, Nordhavnsgården, CopenhagenRBC, Nordhavnsgården, Copenhagen

•Proportional potable water use volumes and wastewater volumes based on Danish water use statistics (DANVA, 2007; Kjellerup and Hansen, 1994; Nordhavnsgården monitoring data).

GW treatment and reuse scenarios

Scenario Treatment type Source of treated greywater Reuse of treated greywater

A No treatment - -

B Indoor – RBC Bathroom Toilet

C Indoor – RBC Bathroom Toilet + Irrigation

D Indoor – RBC Bathroom Toilet + Laundry

E Indoor – RBC Bathroom + Laundry Toilet

F Indoor – RBC Bathroom + Laundry Toilet + Laundry

G Indoor – RBC Bathroom + Laundry Toilet + Irrigation

H Indoor – RBC Bathroom + Laundry Toilet + Laundry + Irrigation

I Indoor – RBC Bathroom + Laundry + Kitchen Toilet + Laundry

J Indoor – RBC Bathroom + Laundry + Kitchen Toilet + Irrigation

K Indoor – RBC Bathroom + Laundry + Kitchen Toilet + Laundry + Irrigation

L Outdoor – reedbed Bathroom Groundwater recharge

M Outdoor – reedbed Bathroom + Laundry Groundwater recharge

Example of a treatment and reuse scenario

Daily potable

water use85 l p-1 d-1

Toilet0 l p-1 d-1

Irrigation0 l p-1 d-1

Bathroom43 l p-1 d-1

Laundry17 l p-1 d-1

Kitchen25 l p-1 d-1

Irrigation7 l p-1 d-1

Laundry17 l p-1 d-1

Toilet27 l p-1 d-1

Surplus33 l p-1 d-1

Scenario K

Potable H2O saving = 51 l p-1 d-1 (43 %)WWTP influent reduction = 20 %

Municipal Wastewater

Treatment Plant61 l p-1 d-1

GreywaterTreatment

Plant85 l p-1 d-1

Sludge

Potable water

Toilet0 µg p-1 d-1

Irrigation

Bathroom3.039 µg p-1 d-1

Laundry4.65 µg p-1 d-1

Kitchen1.58 µg p-1 d-1

Irrigation0 µg p-1 d-1

Laundry0 µg p-1 d-1

Toilet11.155 µg p-1 d-1

Surplus0.109 µg p-1 d-1

Potable H2O saving = 27 l p-1 d-1 (23 %) WWTP influent reduction = 11 %

Municipal Wastewater

Treatment Plant20.229 µg p-1 d-1

GreywaterTreatment

Plant3.039 µg p-1 d-1

Sludge2.735 µg p-1 d-1

[A]

[B]

[C]

[D]

[E][F]

Greywater pollutant dynamics (cadmium)

No decrease in load to

WWTP unless sludge is removed

Decrease in WWTP Cd

influent loading of

2.74 µg p-1 d-1 Potential Cd removal

efficiency of 13.5 %

• Domestic greywater is a significant source of micropollutants to the urban water cycle but there is a lack of knowledge about micropollutant presence and fate in greywater

• Wide range of potential greywater treatment trains and reuse options; combined with the variable pollutant characteristics makes modelling difficult.

• Sludge management is critical in determining the emission barrier potential

• WFD PS/PHS not necessarily highest priority in terms of quantity used and/or risks associated with use

• Need to employ source control measures for decreasing the Greywater pollutant contents (e.g. green labeling and procurement, substitution options, information campaigns, and regulatory controls).

Summary of Greywater Treatment scenarios

On-site treatment systems for industrial wastewater

Industrial wastewater treatment processes appropriate for the removal of suspended solids and insoluble liquids (6 techniques identified as A1 to A6)

• Industrial wastewater treatment processes appropriate for the removal of inorganic/non-biodegradable/poorly biodegradable soluble pollutants (15 techniques identified as B1 to B15)

• Biodegradable soluble pollutants (4 techniques identified as C1 to C4)

Classification of BAT techniques

• CAS number• Emission String number• Production process• NOSE-P classification• Production activity• NACE classification• Possibilities for substitution• Applicable treatment processes• BREF code of relevant document• Treatment efficiency and/or achievable emission levels

Industrial wastewater treatment database for individual PPs

Extract from Cd database (specific treatment)

Applicable treatment processes

BREF code of relevant document

Treatment efficiency and achievable emission levels

A2

Large combustion plant (BREF 07.06)

Waste water from de-sulpurisation plant contains <0.05 mg Cd/l after treatment

B1 combined with A2 or A3 or A4* . B10 **. *** B1 + A2 Speciality

inorganic chemicals (BREF 08.07)

* Cd emission levels <0.01 mg/l. ** efficient removal of Cd and its compounds from low feed concentrations. *** Cd efficiently removed from inorganic pigment waste waters

B1 (co-precipitation at pH 9 with Fe(2+)* . B1 (using sulphide) more efficient than hydroxide precipitation and can be followed by A2 or A4. Combinations of technniques e.g. B1 + A2 followed by A5 and/or B8**

Surface treatment of metals (BREF 08.06)

* Achieves Cd emissions in waste waters of <0.1 mg/l (B10 can be used for further clean-up) . ** Achieves very low metal levels in final effluent.

Extract from Cd database (generic treatment)

A2Wastewater treatment (BREF 02.03)

98% removal

B1 dittoPerformance dependent on situation

B8 dittoNanofiltration achieves >90% removal

B9 ditto Using zeolites as adsorbent

B10 ditto

Cation exchangers (Na) give good removal of Cd and compounds at low feed concentrations

C2 ditto

>99.8% removal when sufficient sulphate present to support sulphide formation; emission levels <0.01 mg/l from influent of 1 mg/l.

Electrodialysis and Reverse Osmosis widely used for soluble Cd

Non-ferrous metal processing (BREF 12.01)

>99.8% removal

Generic treatment options for Cd

Specific treatment option for electroplating wastewaters

• Databases for 25 non-substitutable industrial PPs showing on-site reductions (removal efficiencies or achievable effluent levels) show a variability of data availability and a wide range of different performances.

• Information relating to a specific pollutant is often limited and therefore generic techniques relating to similar pollutant characteristics or overall treatment type are also included.

• The scientific principles involved in the treatment processes together with the equipment and process details are well established.

Summary of Industrial Wastewater Treatment

Municipal wastewater treatment plants

• Removal of pollutants in conventional and alternative wastewater treatment plants

• Fate of priority pollutants in different treatment stages in conventional waste water treatment plants

• Tools to predict the removal and fate of priority pollutants in WWTP

Topics addressed

Example of modelling results for primary treatment

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% Volatilsation % Adsorption % Biodegradation Literrature

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STPWIN Byrns FATE

Percentage removal per mechanism during primary wastewater treatment according to the three tested models

Example of modelling results for secondary treatment

Percentage removal per mechanism during secondary wastewater treatment according to the three tested models for pollutants with log Kow < 4.5

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STPWIN Byrns FATE

Summary of municipal wastewater treatment

• Experimental data exists for 14 of the priority substances originally identified in the WFD

• The removal and fate of an additional 19 priority substances has been predicted using a combination of models (Byrns; FATE; STPWIN)

• Overall, the data collected on 33 priority pollutants can be summarised as:– 19 pollutants presented a removal efficiency higher than 80% (benzene,

naphthalene, tetrachloroethylene, chlorfenvinphos, 1,2,4-trichlorobenzene, pentachlorophenol, endrin, p-p-DDT, fluoranthene, nonylphenols, hexachlorobenzene, 4-para-nonylphenol, benzo(b)fluoranthene, aldrin, benzo(g,h,i)perylene, o-p-DDT, DDE, DEHP and PBDE),

– 12 PPs exhibited removal efficiencies between 50 and 80% (methylene chloride, chloroform, trichloroethylene, carbon tetrachloride, lindane, α-endosulphan, HCH, octylphenols, anthracene, dieldrin, DDD and benzo(a)pyrene)

– 2 PPs (simazine and atrazine) demonstrated removal efficiencies lower than 40%.

PP behaviour in wastewater sludges

and evaluation of sludge disposal options

30

WW treatment systems producing sludge• Municipal wastewater treatment

– e.g. Anaerobic digestion (focus in ScorePP), membrane bioreactors

• Industrial wastewater treatment– e.g. Sedimentation tanks, Coagulation/flocculation, membrane filtration systems

• Stormwater treatment systems– e.g. Sedimentation tank, detention ponds/basins (dry ponds), retention ponds/basins

(wet ponds), constructed wetlands

• Greywater treatment systems– e.g. multi-stage rotating bioreactors, membrane bioreactors, soil filter systems – normal

removal process leads to a build-up of sludge/sediment.

Sludge treatment options• Thickening, dewatering (centrifugal, pressure based, electrokinetic),

stabilisation, conditioning, thermal reduction, sludge pasteurisation, aerobic digestion, anaerobic digestion (mesophilic and thermophilic), drying, composting, storage.

Sludge production and treatment

Summary of sludge treatment

• Primarily designed to reduce volume, odour and pathogenic risk prior to disposal/reuse

• Guideline limits will become increasingly stringent for sludges being disposed of by agricultural land application, landfilling or incineration.

• Reuse options encouraged where feasible e.g. sewage sludge in building materials, metal recovery from electroplating sludge, exploitable by-products.

• The sustainability of many reuse options need careful examination

Assessment of the feasibility of treatment options.

Priority Pollutant Focus

Feasibility assessment has concentrated on 12 PPs.

Agreed criteria for treatment techniques

Screening Criteria Indicators Benchmarks

Technical feasibility Extent to which appropriate technology exists

Level of establishment or development

Technical efficiency Effectiveness of treatment technology

Potential or actual ability of treatment technology to remove target PP

Financial considerations Costs associated with treatment option

Investment costs and operational/maintenance costs

Environmental impact Level of impact on receiving water quality

Average annual dilution required for receiving water to achieve EQS

Scored matrices – Lead example

Treatment type Treatment option Criteria

Tech.Feas.

Tech. Effic.

Financ.Cons.

Env.Imp.

Total score

Pre-Environmental Release Treatment* = Insufficient data available** = Data not calculable as percentage removal efficiency*** = data not calculable as a dilution rate- = Incalculable total score due to data gaps

Industrial treatments

B1 + A2 + A4 1 ** 1 3 -

B1 + A2 1 ** 1 3 -

A4 1 * 1 * -

A4 + B8 1 1 1-2 *** -

A2 1 ** 1 2 -

A4 + B1 + A2 + B10 1 ** 1* 2 -

Municipal wastewater treatment

WWTP 2 3 * 3 -

Post-Environmental Release Treatment

Stormwater BMP treatments

Retention pond 1 3 1 1 6

Infiltration trench 1 3 2 1 7

Infiltration basin 1 2 1 1 5

Porous paving 1 3 2 1 7

Filter strip 1 3 3 1 8

Swale 1 3 1-3 1 6-8

Porous asphalt 1 3 2-3 1 7-8

Settlement tank 1 3 1-2 1 6-7

• A treatment feasibility approach has been developed despite the existence of data gaps and the problems associated with non-comparability of inconsistent units

• Scoring protocols have been allocated according to the available data but may not be suitable for all situations e.g. the relevance of the local context

• Some parameters (e.g. pollutant removal efficiencies; dilution ratios) may be oversimplifications in representing specific criteria.

Summary of treatment feasibility approach

Application to substance flow analysis (SFA) approach

Treatment Barrier Database

38

Assessment of the potential treatments

Information on a selected treatment

Treatment barrier database

• A unit process based approach applied to stormwater treatment by BMPs enables removal of PHS/PS to be assessed.

• Greywater treatment and reuse can make a valuable contribution to potable water savings and WWTP flow reductions but quality improvements are strongly dependent on sludge management

• The existing BAT techniques together with developing treatment options demonstrate taht a comprehensive range of efficient options are available for the industrial control of PPs in process waters.

Conclusions

• A combination of experimental and modelling data provides relevant information regarding the removal of PHS/PS in conventional WWTPs.

• Sludge treatment needs serious future consideration as it is becoming increasingly unacceptable to practice current disposal routes for contaminated sludges.

• A treatment feasibility approach has been developed and provides the basis for a multi-criteria analysis.

Conclusions (continued)