http://www.unep.or.jp/ietc/Publications/Freshwater/FMS1/3.asp

Newsletter and Technical Publications

Freshwater Management Series No. 1

Biosolids Management: An Environmentally Sound Approach

for Managing Sewage Treatment Plant Sludge

An Introductory Guide To Decision-Makers 

Practices In Europe and North America: Waste Disposal Versus Resource
Utilisation

Throughout North America and Europe, the application of biosolids to
land is continuing to increase. As shown in Table 1, current biosolids
applications to agricultural land in Europe and North America has become
significant. 

Although biosolids disposal in a landfill site is common, it should not
be viewed as a long term solution. This option is considered to be
environmentally beneficial only when such disposal includes methane gas
recovery for application as a fuel. Modern landfills are complex and
costly facilities to build and operate. They must be carefully
engineered and monitored to ensure protection of both groundwater and
surface water. In many locations, accessible, long-term landfill
capacity is limited. Engineering and siting requirements can make the
construction of new landfills prohibitively expensive. Most importantly,
landfill disposal does not take advantage of the nutrient value and
soil-building properties of biosolids, and takes up landfill space that
can be better used for other materials. However, landfill is the
unavoidable choice when municipal sludge is contaminated with industrial
waste and municipal authorities are unable to monitor and control
industrial discharges.

Table 1: Biosolids Management Method in European Nations and in the
United States



Annual

Production

Mangagement method

(percentage of total)

 

(1,000 dry tons)

Agriculture

Landfill

Incineration

Other

Austria

320

 

13

 

56

 

31

 

0

 

Belgium

75

 

31

 

56

 

9

 

4

 

Denmark

130

 

37

 

33

 

28

 

2

 

France

700

 

50

 

50

 

0

 

0

 

Germany

2500

 

25

 

63

 

12

 

0

 

Greece

15

 

3

 

97

 

0

 

0

 

Ireland

24

 

28

 

18

 

0

 

54

 

Italy

800

 

34

 

55

 

11

 

0

 

Luxembourg

15

 

81

 

18

 

0

 

1

 

Holland

282

 

44

 

53

 

3

 

0

 

Portugal

200

 

80

 

13

 

0

 

7

 

Spain

280

 

10

 

50

 

10

 

30

 

Switzerland 

50

 

30

 

20

 

0

 

50

 

UK

1075

 

51

 

16

 

5

 

28

 

US

5357

 

36

 

38

 

16

 

10

 

Total/Avg.

11988

 

38

 

43

 

10

 

9

 



Source: Chang, Page, and Asano, 1996

From an environmental point of view, incineration of biosolids is also a
very limited disposal option. The ash produced in the incineration
process must be treated as a hazardous waste because it contains high
levels of heavy metals. Incinerators require significant capital
investment and have relatively high operational costs. Because biosolids
have a high percentage of water (70% - 98%), the energy costs can be
significant, although some energy can be recovered by burning the
organic material. Expensive and sophisticated air pollution control
systems are needed to remove particulates and regulated gases from
incinerator smokestacks. Like landfill disposal, incineration does not
take advantage of the nutrients and soil-building qualities in
biosolids. Incineration is occasionally used for biosolids disposal in
urban areas where the population is large, suitable agricultural land is
far away and transportation costs are prohibitively high.

Addressing Public Concerns about the Land Application of Biosolids

Opposition to land application has usually centred on local issues, such
as resistance of rural communities to receiving shipments of urban
biosolids. Apart from this, the most pervasive public concern about the
land application of biosolids is the perception that toxic trace
elements and pathogens may be released into soil and groundwater. 

Biosolids often contain concentrations of trace elements greater than
the concentrations found in typical soils; therefore, biosolids
application may potentially increase the concentration of these
elements. Most trace elements, however, are immobile and tend to
concentrate in the soil only to the depth that biosolids are applied.
The National Research Council in the United States has determined that
where properly processed biosolids have been applied to soil according
to specific guidelines and regulations, there has been no evidence of
phytotoxicity or accumulation of trace elements in plants. If the
agricultural use of biosolids follows appropriate regulations, including
Ph requirements, no adverse effects should be expected or observed.

Communities are also concerned about the possibility of disease
transmission since pathogens are present in the untreated sewage from
which the biosolids are produced. In fact, pathogen populations are
significantly reduced through the wastewater treatment and biosolids
production processes, as well as through full compliance with regulated
land application requirements. In the United States, for example, where
biosolids utilisation accounts for more than half of the residual solids
output, there have been no documented cases of diseases resulting from
either treated wastewater reuse or agricultural use of this material.
Furthermore, no adverse effects have been reported from ingestion of
plants grown in biosolids-treated soils. It is essential, however, to
have a fully functioning, environmentally sound biosolids management
system in place to ensure public and environmental health protection.

In most communities, the land application of biosolids is usually
limited to marginal or agricultural lands that are used for either
animal feed or crops that are not ingested raw. For specialised
commercial applications such as composting or horticultural uses, a
higher degree of stabilisation is usually necessary.

A Range of Options for Biosolids Utilisation

The most successful and best-known biosolids utilisation practices are
as follows:

 	• 	Agricultural cropland application, through liquid injection, or
surface spreading followed by incorporation into the soil, 

 	• 	Commercial sale as a fertiliser or soil conditioning material,
particularly for horticultural and landscaping applications (although a
higher degree of stabilisation is usually necessary),

 	• 	Rangeland and pasture application to improve available grazing,

 	• 	Remediation of contaminated areas such as mine sites,

 	• 	Soil amendment and recovery of marginal land,

 	• 	Land application in reforested areas, and

 	• 	Energy recovery.

In most cases, the option is determined by a careful cost-benefit
analysis and the size and characteristics of the market for the product.
Local markets usually need to be fostered through education,
demonstration and training. When considering land applications of
biosolids, it is important to ensure that concentrations of metals and
complex organics do not exceed stringent regulatory limits. It is also
essential to understand the soil properties and crop characteristics of
those land areas being considered for land application of biosolids. To
reduce risk, frequent, ongoing applications at the same site should be
avoided.

