Long-term aftercare
4.1 MBP research and practice in Austria
4.1.1 Data from full-scale MBP landfills in Austria
Although large quantities of MBP material are produced, there are few, if any, sites where only MBP wastes are disposed. Some MBP composts are used in agriculture. Other composts are subjected to different degree of treatment – for example, the fraction less than 25 or 30 mm is typically composted for about 20 weeks, but larger fractions up to 60 or 70 mm often have much shorter pre-treatment of only about 3 days. In some landfills the two fractions may ultimately be disposed of together, often in combination with other waste fractions such as demolition wastes or sewage sludges, in various proportions.
A student at the Universität für Bodenkultur in Vienna, Helmut Wurz (Wurz, 1999) has undertaken a diploma thesis in this field, to look at a number of Austrian landfills that have received significant inputs of MBP wastes. Some of these sites were still operational, while other had closed. Inevitably, different proportions of MBP wastes had been landfilled at each site, having been pretreated to different extents.
He tried to look at differences in leachate quality from each site, and then to relate these to received waste inputs. Wurz looked for both “old” and “young” landfill sites in 3 categories:
• no MBP wastes received;
• about 20 percent MBP wastes received; and
• 50 percent or greater input of MBP wastes.
Wurz was unable to find any young sites containing about 20 percent MBP wastes, but obtained data for each of the other five site combinations, and published these in detail in his thesis (Wurz, 1999 – in German). Data was obtained from 12 landfills, covering various periods and of variable quality. For the purposes of this review, we have concentrated on data from 4 landfills, selected as 2 pairs of sites – one pair of young sites and one pair of old sites. For each pair, one site provides leachate data for non- pretreated wastes, and the second site provides comparative data for leachate from wastes including at least 50 percent MBP domestic waste. The 4 sites are as follows.
Breitenau comprises a large experimental landfill that was established during 1987-88, about 50 km south-south-west of Vienna, to investigate the release of contaminants from landfilled household wastes, and their potential impacts on groundwater quality. The site was constructed and lined as 3 separate cells, termed “Fields 1, 2 and 3”. Fields 1 and 2 are of most interest to the present study, having received 35,000 t and 25,600 t respectively (wet weight) of non-processed MSW from Vienna (subject to separate collection of biowaste), emplaced to a depth of about 8 m. Wastes were emplaced during a 12-month period to September/October 1988 (Binner and Lechner, 1995; Binner 1996b; Rank et al., 1992; Binner et al., 1997b; Riehl-Herwirsch and Lechner, 1995; Wurz, 1999). The main
difference between the two cells was that Field 1 was provided with a low permeability cap, whereas Field 2 had a relatively high permeability top cover. Leachate data have been obtained for the period from early 1988 to mid-1995.
Attnang-Redlham landfill site is located about 120 km south west of Vienna, and has received about 20,000 t of waste each year since 1975. Before 1995, just residual wastes were being deposited, but subsequently composted waste has been landfilled, and has comprised 80% of the incoming waste streams. Other inputs include 10% commercial wastes, 5% bulky wastes, and 5% demolition wastes.
Total depth of the site is about 18 m. Incoming pulverised residual MSW is wetted with landfill leachate (no sewage sludge enters the site), to be placed in windrows and naturally aerated for about 6 months.
It is turned about 2 or 3 times and disposed of without further treatment. Leachate data exist for the period 1980-1998.
Halbenrain is located about 40 km south of Graz, in southern Austria, and received 70,000 t/a of residual wastes, with no pre-treatment, between 1979-1991. The waste comprised 70% commercial wastes, 8% bulky wastes and residual wastes, with 22% of other wastes (including sewage sludge with 30% dry solids, plus primary sewage screenings. Data exist for leachate quality from 2 areas of the site, for the period 1993-1998.
Ort/Innkreis is about 25 km from the town of Linz, and received MSW from 1974-1980, before composting of residual wastes began at the site. About 20,000 t/a of incoming wastes have received mechanical and biological pre-treatment, and these MBP residues comprise about 50% of the total landfill inputs. No sewage sludge or screenings are accepted. The whole incoming MSW spends 36 hours in a Dano drum, being sieved to 120 mm afterwards, and subsequently to 10 mm. The fraction greater than 10 mm goes directly for disposal, and the smaller fraction receives “natural aeration” in unturned windrows for a few months. 4000 t/a of this fraction is used for agriculture, and the rest is landfilled – achieving a density of about 0.9 t/m3.
Breitenau and Attnang-Redlham
Results from the first pair of sites represent leachate quality data from two landfills with both “young”
wastes and “older” wastes, including results for the period from 2 years before and up to 6 years after closure of the landfills.
Figure 4.4 compares BOD5 values in leachates from the two landfills, data being normalised with respect to the dates on which the sites stopped receiving waste inputs. Leachate from the non- pretreated wastes contained much higher BOD values (to 30,000 mg/l) than that from the 80% MBP wastes, but within 2 years of site closure, BOD values in both leachates had fallen to similar low values.
Figure 4.5 presents equivalent data for COD values, confirming both this conclusion, and also the fact that untreated MSW residual wastes can give rise to very high organic strength leachates.
Figure 4.6 provides comparative data for pH-values at the two sites, and results at both sites reflect the onsets of methanogenic conditions. Results for concentrations of ammonium, given in Figure 4.7 are both more variable and less conclusive, but values typically remain above 500 mg/l for both sites, at
0 5,000 10,000 15,000 20,000 25,000 30,000 35,000
-2 -1 0 1 2 3 4 5 6
years before or after end of tipping BOD5 mg/l
Breitenau (non-pretreated) Attnang-Redlham (80% MBP wastes)
Figure 4.4 Comparison of BOD5 values in leachates from Breitenau (field 1) containing untreated residual wastes, with leachates from Attnang-Redlham that has received 80 percent MBP wastes (Wurz, 1999)
0 10,000 20,000 30,000 40,000 50,000 60,000 70,000
-2 -1 0 1 2 3 4 5 6
years before or after end of tipping
COD mg/l
Breitenau (non-pretreated) Attnang-Redlham (80% MBP wastes)
Figure 4.5 Comparison of COD values in leachates from Breitenau (field 1) containing untreated residual wastes, with leachates from Attnang-Redlham that has received 80 percent MBP wastes (Wurz, 1999)
5.00 5.50 6.00 6.50 7.00 7.50 8.00 8.50 9.00
-2 -1 0 1 2 3 4 5 6
years before or after end of tipping
pH-value
Breitenau (non-pretreated) Attnang-Redlham (80% MBP wastes)
Figure 4.6 Comparison of pH-value in leachates from Breitenau (field 1) containing untreated residual wastes, with leachates from Attnang-Redlham that has received 80 percent MBP wastes (Wurz, 1999)
0 500 1000 1500 2000 2500 3000
-2 -1 0 1 2 3 4 5 6
years before or after end of tipping
Ammonium mg/l
Breitenau (non-pretreated) Attnang-Redlham (80% MBP wastes)
Figure 4.7 Comparison of concentrations of ammonium in leachates from Breitenau (field 1) containing untreated residual wastes, with leachates from Attnang-Redlham that has received 80 percent MBP wastes (Wurz, 1999)
Halbenrain and Ort/Innkreis
Data from the second pair of sites provide a much clearer comparison. Both sites are old sites, the former having received non-pretreated wastes, the latter an input of 50% MBP wastes since 1980.
Figures 4.8 and 4.9 provide comparative data for BOD5 and COD respectively, and demonstrate the much higher organic strength of leachates from the non-pretreated wastes, where COD continues to exceed 12000 mg/l, of which measured BOD5 comprises nearly half.
This is surprising, since pH values in excess of 8.0 at each site (see Figure 4.10), would normally indicate establishment of methanogenic conditions. The much higher polluting potential of the unpretreated wastes at Halbenrain (which include sewage sludges) are apparent in continuing
concentrations of ammonium above 4000 mg/l (see Figure 4.11), which have previously exceeded 8000 mg/l during 1993, two years after closure of the site.
0 5,000 10,000 15,000 20,000
1993 1994 1995 1996 1997 1998
BOD5 mg/l
Halbenrain 14
(non-pretreated wastes 1979-1991) Ort/Innkreis
(50% MBP wastes since 1980)
Figure 4.8 Comparison of BOD5 values in leachates from Halbenrain 14 containing untreated residual wastes, with leachates from Ort/Innkreis that has received 50 percent MBP wastes since 1980 (Wurz, 1999)
0 5,000 10,000 15,000 20,000 25,000 30,000 35,000
1993 1994 1995 1996 1997 1998
COD mg/l
Halbenrain 14
(non-pretreated wastes 1979-1991) Ort/Innkreis
(50% MBP wastes since 1980)
Figure 4.9 Comparison of COD values in leachates from Halbenrain 14 containing untreated residual wastes, with leachates from Ort/Innkreis that has received 50 percent MBP wastes since 1980 (Wurz, 1999)
5.00 5.50 6.00 6.50 7.00 7.50 8.00 8.50 9.00
1993 1994 1995 1996 1997 1998
pH-Value
Halbenrain 14
(non-pretreated wastes 1979-1991) Ort/Innkreis
(50% MBP wastes since 1980)
Figure 4.10 Comparison of pH-value in leachates from Halbenrain 14 containing untreated residual wastes, with leachates from Ort/Innkreis that has received 50 percent MBP wastes since 1980 (Wurz, 1999)
0 4,000 8,000 12,000
1993 1994 1995 1996 1997 1998
Ammonium mg/l
Halbenrain 14
(non-pretreated wastes 1979-1991) Ort/Innkreis
(50% MBP wastes since 1980)
Figure 4.11 Comparison of ammonium values in leachates from Halbenrain 14 containing untreated residual wastes, with leachates from Ort/Innkreis that has received 50 percent MBP wastes since 1980 (Wurz, 1999)
Wurz (1999) provided overall summaries of the results from all of the sites that he examined, expressed in terms of maximum, minimum and mean values for each contaminant in leachates from each specific waste input landfill. Figures 4.12 to 4.16 below provide results for COD, BOD5, pH-value, ammoniacal- N and Zn.
Results presented confirm both the potential high organic strengths of landfilled residual wastes that have not received MBP, and the more rapid onset of methanogenic conditions that can be achieved in wastes that have. However, the data shown, and also the more detailed results that Wurz includes within his thesis, indicate that less significant reduction in concentrations of ammoniacal-N and zinc (and also for nickel and copper) is achieved in the early years following landfill of MBP wastes. The data do indicate that concentrations of these contaminants in leachates reduce more rapidly in the period after 3 years following deposit.
0 10,000 20,000 30,000 40,000 50,000 60,000
no MBP wastes
(fresh) no MBP wastes
(old) 20% MBP wastes
(old) >50% MBP wastes
(fresh) >50% MBP wastes (old)
COD mg/l
Figure 4.12 Ranges of COD values in leachates from various landfill ages receiving wastes containing different proportions of MBP wastes (Wurz, 1999) (mean value shown as black square)
0 5000 10000 15000 20000 25000 30000 35000
no MBP wastes (fresh)
no MBP wastes (old)
20% MBP wastes (old)
>50% MBP wastes (fresh)
>50% MBP wastes (old)
BOD5 mg/l
Figure 4.13 Ranges of BOD5 values in leachates from various landfill ages receiving wastes containing different proportions of MBP wastes (Wurz, 1999) (mean value shown as black square)
6.00 7.00 8.00 9.00
no MBP wastes (fresh)
no MBP wastes (old)
20% MBP wastes (old)
>50% MBP wastes (fresh)
>50% MBP wastes (old)
pH-Values
Figure 4.14 Ranges of pH-values in leachates from various landfill ages receiving wastes containing different proportions of MBP wastes (Wurz, 1999)
(mean value shown as black square)
0 1000 2000 3000 4000 5000 6000
no MBP wastes
(fresh) no MBP wastes
(old) 20% MBP wastes
(old) >50% MBP wastes
(fresh) >50% MBP wastes (old)
Ammonium mg/l
Figure 4.15 Ranges of concentrations of ammonium in leachates from various landfill ages receiving wastes containing different proportions of MBP wastes (Wurz, 1999) (mean value shown as black square)
0 5 10 15
no MBP wastes (fresh)
no MBP wastes (old)
20% MBP wastes (old)
>50% MBP wastes (fresh)
>50% MBP wastes (old)
Zinc mg/l
Figure 4.16 Ranges of concentrations of zinc in leachates from various landfill ages receiving wastes containing different proportions of MBP wastes (Wurz, 1999) (mean value shown as black square)