~ Pergamon Waf. Sci. Tech. Vol. 38. No.2. pp.97-102.1998.

. IAWQ=.1998,Pubhshed by Elsevier Science LId.PrintedIn GreatBritain. All rightsreserved

PH: S0273-1223(98)00434-X 0273-1223/98 $19'00 + 0'00

SUSTAINABILITY IN BIOSOLIDSMANAGEMENT

Peter Matthews

Anglian Waterlntemational; AnglianHouse. AmburyRoad, Huntingdon, PE186NZ,UK

ABSTRACf

The paper reviews the latest position in interpreting the Global Atlas of sludge and biosolids managementlaunched at the last biennial conference. It uses the principle of sustainability as a benchmark concept andgives examples of how this would look against the practical operations of Anglian Water in Eastern England.© 1998 Published by Elsevier Science Ltd. All rights reserved

KEYWORDS

Biosolids; sustainable management; utilisation.

THE CONCEPT OF SUSTAINABILITY

In Europe and the UnitedStates sludgemanagement is a very important feature of wastewater management.Production is expected to rise as investment in environmental water management increases and moremunicipal wastewater is treated to even higherstandards. At the same time environment protection policiesare making the disposal and use.(as b~osolids) mo~e ~iffic~lt. In both continents the principal future optionsare expectedto be biosolidsuse In agncultureand incmeration (Matthews 1996; Walshand Donovan, 1996).

It is understood that following the Brundtland Report (1987) sustainability is development which meets theneedsof the present withoutcompromising the abilityof future generations to meet their own needs.

The treatmentof municipal wastewater produces a sl~d~e ~hich must~ disposed of. The preferredway isby treating the product as a useable resource. So, as It IS likely that society IS going to produce wastewaterfor a very long time, the method of disposal or use of the solidproductmusthave an equally long longevity.

For practicalpurposes a sustainable policyfor the management of wastewater solidsshouldhave measurablefeatures. An attemptat defininga weighted index is given frompractical experience. These are summarisedin Table 1. The weighting reflects the expe~ences .of the author, different ~ultu~s ~d experience mayproducedifferentweighting. An attemptat usmgthe Jnd~x for a numberof options IS given in Table 2. Thisis in effect an attemptat an "eco-points" systemfor the disposal of wastewater solids. Its purpose is to focusattention on the key issuesand to stimulate further investigation and discussion - which was the outcomeofthe presentation in the Vancouver Biennial.

97

98 P. MATI'HEWS

Table 1. An approach to quantifying biosolids management sustainability

Objective I.... lodn ",.ightillc

A No WllIl:CCpt&ble HeavymctaIcontamination Iuts a lolllltime 9environmental imr-:t

B No impact on human Oi_CUI be lrcaledbut c:oostant~infec:lion is expensive and dcbililatiDg 6health

C Publicacceptance Publicviews can be illJ'Oted but !luI is aociallywrona and difficultto operate. 6Fumen acceptance is important.

0 Affordabibty MODC)' call be providedfor 11ft)'opcnIion but if it is IIDIIeCeIIlII)' cxpcoditure it 3divau rnoun:cs from othermorewmb)' _ Securityis abo a fK1or.

E Resource recovery Ultimately sludae is produced DOt dclibcntel)'.. a raoun;e butrcsourcerecovery is 3prefCl1lble. If our nonrecovery wu prcfa'able00 allolbet'countsthis wouldbeIIICd

Table 2. Biosolids management sustainability indices

DiJpoaaVU....Optias ladnA D C D E TOTAL

Agricultural 11M Highmctals' Shortndius of use 3 6 4 2 2 17

Lollllndius 3 6 4 I 2 16MediummctaIs' Sbortndius 6 6 5 3 3 23

Lonandi us 5 6 5 2 3 21Lowmetals' Sbortndius 9 6 6 3 3 27

Longradius • 6 6 2 3 25lnc:ineration . Landfill uh 6 6 3 I 0 Ii

Uscofuh Sbortradius 7 6 4 2 I 20Landfill, direct ~ 6 3 2 0 14, thisma)'a150 apply to I)'lltbeticorpIIICI

This ranking is quite crude and is not as sophisticated as could be achieved by many computer models.However, it produces a ranking which feels right, in a situation such as that in Anglian Water; the contentcan be the subject of more sophisticated statistical opinion ranking techniques. It assumes good practice inall the operations. As one would expect, the use of appropriately treated low metal biosolids, fairly close tothe originating works scores highest. The score may be refined by having a perception of how metals behavein the soil environment.

The ranking assumes access to all opportunities for disposal but local practical constraints may limit theoptions. So, for example, in Tokyo the option cannot include agricultural use and the ranking ofsustainability will have to distinguish between solutions such as incineration plus landfill of ash,vitrification, brick manufacture and so on.

Models to optimise sludge management over a long period of time, such as WISDOM in the UK producedby the Water Research Centre, are used already and could be extended to account for sustainability moreexplicitly. The application of the techniques of life cycle analysis and environmental management systemsare also being examined, for instance in Anglian Water in the UK, to determine their usefulness. It isimportant 10 remember that management sustainability models are based on the assumption of sustainabilityof the environmental criteria underpinning. So, for example. models of sustainability for the agricultural useof wastewater biosolids are based on the premise that soil quality criteria permit the sustainable use of soil.This paper concentrates primarily on the influence of metals on sustainability.

Models defining the behaviour of metals in soil have been examined. For the sake of simplicity at oneextreme we can assume a static model (loss of organic matter. no loss of metals by crop uptake or leachingor soil biotic activity), and the rate of accumulation of metals in the cultivated layer may be calculatedsimply. The number of return visits to achieve a maximum acceptable soil concentration may then becalculated. At the other extreme it can be assumed that all of the organic matter is conservative . This woulddilute the soil but reduce the bulk density and would give a greater number of return visits. Reality will bebetween these extremes, with organic matter degradation depending on many environmental factors. A

Sustainability in biosolidsmanagement 99

working model has been developed in Anglian Water - it is assumed that soil depth accumulates at 02mm

per year with addition of 5 dt/ha per year with 25% inorganic ~atter in the dry solids and 50% of the organic

matter degradable at I% per year. Losses of metals by leaching were considered insignificant. (Wilkinson

and Matthews, 1996). Information will be provided on the relationships of soil quality criteria and biosolids

quality .

The soil concentration limits will have to be set taking into account all of these factors, in order to prevent

zootoxic and phytotoxic effects in the crops and pasture as well as protection of the soil ecology.

In extremis, the ideal goal is to have a situation in which an infinite number of visits can be made; a metal

free biosoJid would do that, but. as has happened in the Netherlands. the imposition of much tighter limits on

biosolid and soil quality and application rate in order to ensure sustainability has rendered, in the view of the

Dutch. agricultural use an unsustainable operation; Dutch biosolids will be incinerated. This can be

rationalised in the Index, as given in Table I, by dropping affordability to O. acceptability to O. because of

the low rate of application (fanners views) and long radius operations with the impact of transport will score

8 for environmental impact. It scores less than incineration on affordability because in the potential Dutch

situation it could be a less secure operation. So in total it scores 17. So the paradox is that in an attempt to

create a more sustainable operation. the solution is to adopt a practice which, by general assessment. is less

sustainable.

In a biosolids utilisation operation which is working to finite criteria, all the land. by definition will be used

eventually. So if biosolids are applied annually and the soil quality objective is attained in 30 years and 2%

of available land is used, the operation will have a life of 1500 years. There will be a progressively lessening

sustainability rating because of the gradually increasin~ distances which will have to be covered (assuming

that the nearest are served first). So what should consnrute a reasonable target for "site life" (i.e. number of

return annual visits - this may be extended by visiting less frequently) from our current view point i.e. what

is a sustainable operation?

It would seem reasonable to develop a concep! of gener~tionsof 'p~~ula~ion with one generation being 25

years ; two generations of people (50 years) gIves sufficlcnt flelllblllty In terms of operations. but leaves

opportunity for monitoring and res.earch. to develop new ~e~ods of utilisation - possibly with an emphasis

on resource recovery. but eccnormcs wIll playa role. This IS not the dump and monitor philosophy, but a

cautious policy which is slow enough to allow any adjustment as new information becomes available.

11IE COMPARISON OF PRACTICES FOR SOIL QUALITY

MANAGEMENT IN EUROPE AND THE USA

These ideas have been developed within a framework provided by the Global Biosolids Network - primarily

by co-operation of IAWQ. EWPCA and ~. The ~etwork pr~uced a Global Atlas of Waterworks,

Biosolids and Sludge Use and Disposal which was publtshed at the time of the Singapore Biennial in 1996.

The model of sustainability was produced as a platform to support critical comparison of different national

practices.

The future of sludge disposal is predominantly incineration with a variety of disposal and use methods for

the ash or use as biosolids.

This paper examines the detail of sustainability for biosolids management for the view of zinc. lead and

cadmium. In practice a wide ell.aminati~n would be need~d. For the purposes.of~re.vity it is ~sumed that the

treatment of the biosolids avoids public health and nuisance problems which It IS recognised are vital in

terms of short term sustainability.

If an operation causes disease or annoys the public, it win come to an abrupthalt and arguments about long

term sustainability are irrelevant.

100 P.MATIHEWS

So how do the metal limits compare for a 5 dry tonneslha per year operation using Cd, Pb and Zn asindicators? A 20cm cultivated depth and background soil values of 0.1mg Cdlkg, 20mg Pblkg, 40mg Znlkgat pH 7 are assumed unless stated otherwise. Table 3 provides information based on a worst case scenariofor the soil model as described earlier. In each case the lowest site life is the rate determining metal for thebiosolid ,

Table 3. Comparative site lives

US EC UK Netherlands Sweden Spainupper operationalvalues

Alol Blbl A A Blcl A B A B(d) A B(OII

Cd 200 1300 47 50 302 .(~I Ofl'l 100()lC) 1040,0/ 47 83

Pb 200 314 152 48 545 .Ikl OF") 2080\1/ 2080"/ 152 156

Zn 200 454 43 45 118 .Ik) OFI') 1501111 150\11 43 222

Notes :A : Site life based on RegulationsB : Site based on Regulations but using typical biosolids quality(0): Final soil concentrations 14.1mg Cdlkg, 135mg Pb/kg, I 120mg Znlkg, using exceptional quality(h) : Philadelphia (IAWQ 1996) (c) : Anglian Water (4): Goteborg (IAWQ 1996)(0) : 2.6dt/7 years (I) : 1.8dt/7 years II) : 5.3dt/7 years(h) : 3.8dt/7 years (,) : 3.8dt/7 years OJ : 5.6dt/7 years(It) : 2dt/yr (I) : OF Operations Finishing(01) : Catalunya (1996) background 0.25mg Cd/kg, 20mg Pb/kg, 60mg Znlkg

The interpretation of sustainability is more difficult. A number of issues are evident.

(i) Operational sustainability may typically be better than the regulatory sustainability which acts as aceiling. If the difference is large it is pertinent to pose the question - is there benefit by maintaining thehigher regulation ceiling values on soil or biosolids? Protecting the disposal of extremely poor qualitysludges is no longer viable in terms of public acceptance, however justifiable this may be in scientific andenvironmental terms. The regulations should hang together. Are the US regulations based on 50 drytonneslha per yr (2Ocm cultivated depth)?

(ii) Sustainability may be comparable in terms of site visits but the "envelopes" may be different i.e. ultimateconcentrations and even the rate of accumulation may be higher in one case compared to another. So whatwould be sustainable in one country would not be sustainable in another country. The higher "envelopes"will be less sustainable in terms of the index discussed earlier. All of the ongoing operations are sustainableby virtue of the criteria defined earlier i.e. exceed 50 years in terms of operations within local criteria.

However affordability in different parts of Europe and in the US will vary and affect the local values of thesustainability index. It is worth commenting, however, that the average transatlantic citizen is likely to spendas much, if not more, on newspapers as they do on wastewater solids management.

(iii) As discussed before some agricultural operations have become unsustainable because the criteria havebecome too demanding. The view of some European countries is to take the precautionary approach and gobeyond the scientific evidence and limit the spread of metals as much as practically possible. This hasimplications for control of metals at source beyond good industry husbandry and means regulating the use ofthe chemicals in homes.

Sustainability in biosolids management 101

SUMMARY OF PRINCIPLES APPLIED TO BIOSOLIDS MANAGEMENT

The principles of sustainability are already emerging albeit not recognised explicitly under that descript]

In terms of these concepts each continent and each country has made sincere efforts to establish sustain~~~'

sludgelbiosolids management laws, policies and practices. It is interesting in sociological terms to note the

difference in the results of these efforts even in the interpretation of the basic facts. e

The really difficult aspect arises when it is suggested that the criteria are migrated from one country to

another. If this is to happen, a lot more work is needed to establish some basic common facts and leave each

country to use them as it thinks fit. An analogy is the use of toxicity data. The basic facts are, nil effect dose

or LD or LC; these are applied using application factors, such as 0.01, to calculate safe environmental

exposure. Such factors may be derived using the different approaches to interpretation of scientific data and

environmental philosophies. So for example, we can pose the question: what is the critical pathway for zinc

in biosolids use and what are the appropriate toxicity criteria? At the moment the answer is the effect on

crops or effect on soil microbes and the soil criteria range 75 to 7500 mg/kg dry solids depending on where

you live.

Whatever happens the approaches should leave scope for safe use and disposal. A sustainable policy cannot

leave piles of wastewater solids in the comer of treatment works awaiting a solution.

In spite of the fact that there is debate about some aspects of using biosolids principally in agriculture

forestry etc. sensible use makes good sense and is a sustainable environmental practice. '

The biggest immediate threat to the sustainability of operations in both the US and EU is public acceptance

so problems like bad smells can be more threatening than some of the concepts relating to metals. The public

need to be reassured on the short term public health threat. So whilst the long term concept of sustainabiIity

is based on the risks arising from the accumulation of potentially toxic chemicals in the environment and

food chain, it rests on the presumption that there are no short term hazards, without that presumption any

operation can only be considered as having limited sustainability.

It may well be that quality assurance systems such as ISO 9000 and environmental management systems

SUch as ISO 14000 will not only sustain public confidence but assist managers in maintaining sustainable

operations.

The elements of a sustainable policy for agricultural use which includes criteria for public health and

acceptance are proposed as :

Set soil quality criteria which ensure safe use in perpetuity i.e, there should be an underpinning

policy for sustainable use of soils;Ensure that these criteria are achieved in a period of more than 50 years of biosolids application;

The biosolids application is safe in health terms;

The practice is acceptable to the public and customers;

The operation should be affordable;

It should score highly in eco audit systems.

In this context there is fairly good agreement between Europe and the US on what constitutes a sustainable

operation. Where there is some divergence on the attitude of what constitutes sustainable soil use and if

there is to be any convergence of policies it must be based on a sound understanding of why there are

differences.

The paper forwards some principles for a sustainable operation, ~t should. be non hazardous, acceptable,

affordable and last for at least two generations. We have plenty of time to think about what to do in the very

long term but we should not wait. We need to d? the. researc~ no~ so that we have new sustainable

operations, maybe resource recovery, as an alternate inheritance; this Will, of course, be more expensive!

102

ACKNOWLEDGE.'dENTS

P. MAlTHEWS

The author acknowledges the permission of Anglian Water to present the paper. Any views expressed arethoseof the authorand not necessarily thoseof Anglian Water.

REFERENCES

IAWQ. EWPCA. WEF (1996). Global Atlas of Wastewater Sludge and Biosolids Use and Disposal. IAWQ Scientific andTechnical ReportNo.4. London. UK.

Matthews. P.1. (1996). European Progress on the Political and Economic Concerns of Sludge Disposal- Is the Future Biosolids orAsh? EWPCA-NV A Conference. Future o/Water Quality Management in Europe. Aquatech, Amsterdam.

Walsh. M. 1. and Donovan, J. F. (1996). Current Trends in Biosolids Management Practices. tOth EWPCA Symp. SludgeTreatment andRe-Use. Munich.

Wilkinson. D. E. and Matthews. P. J. (1996). Internal Anglian Water communication. Huntingdon. UKWorld Commission on Environment and Development (1987). Our Common Future. G. H. Bruntland (Chairperson) . Oxford

University Press.Several authors (1996). In: Ponencies de les Jourardes sabre la Reutilisacio de Fangsde Depuracio d' AigUes Residuals Urbanes.

Generalitat de Catalunya. Department de Medi Ambient. Juntes de Saregament, Barcelona.