Tertiary treatment of municipal wastewater in a floodplain ... · Tertiary treatment of municipal...

Tertiary treatment of municipal wastewater in a floodplain peatland

M. Öövel, R. Tarajev, A. Kull & Ü. Mander Institute of Geography, University of Tartu, Estonia

Abstract

In August-October 2002 we used an experimental plot established in a semi-natural sedge-willow dominated floodplain peatland on the Valgejõgi River, Estonia, to study the purification of effluents from a conventional sewage treatment plant treating municipal wastewater from the town of Tapa and effluents from a distillery in Moe village (about 25000 pe). From the early 1960s to 1997, over 18 ha of this floodplain was used for the treatment of raw wastewater from Tapa and Moe. The retention of organic matter (BOD5), mineral nitrogen (N), and total phosphorus (P) during the vegetation period was 96, 98, and 88%, and in winter 56, 62, and 27% respectively. Due to the very high initial load, however, the river quality downstream worsened. After the construction of the sewage treatment plant in 1997, the water quality improved, although concentrations of Total P (5 mg l-1 on an average) and nitrate N (sometimes <20 mg l-1) in the outflow remain higher than acceptable for sensitive water courses. Thus there is a need for tertiary treatment of purified wastewater. Our experiments on an experimental plot (21×31m, hydraulic load 60 m3 d-1) showed that removal of Total N and Total P was 25-30% and 68-75% respectively. Reduction of NO3-N concentrations was between 50-85%. Keywords: ammonia nitrogen, BOD5, denitrification, floodplain peatland, nitrate nitrogen, total phosphorus

1 Introduction

Peat has been widely used in the treatment of wastewaters of various origin and quality. Several laboratory and field experiments show that peat as filter material in trickling filters, biofilters and other conventional treatment systems can effectively mineralize organic material, remove suspended solids and

© 2005 WIT Press WIT Transactions on Ecology and the Environment, Vol 80, www.witpress.com, ISSN 1743-3541 (on-line)

Water Resources Management III 433

nitrogen [1, 2, 3, 4, 5, 6, 7, 8, 9], remove pathogenic bacteria [7, 8, 10, 11], retain phosphorus [12, 13] and different heavy metals [14, 15, 16]. Some peats retain satisfactory hydraulic conductivity for years [17], whereas some well mineralized peats can become quickly clogged [4, 18]. On the other hand, there is a limited number of peatland systems used for wastewater treatment. In Finland, for instance, the overland-flow peatlands effectively remove suspended solids, nitrogen and phosphorus in the wastewater from peat mining areas [19, 20, 21, 22]. In Canada and the US, most peatland filters treat domestic wastewater [23, 24, 25], while one system showed very good performance in treating landfill leachate [26]. The long-term (1979-2000) efficiency of domestic wastewater treatment was demonstrated by an 8.3-ha peatland filter in northern Wisconsin, USA [27]. Some floodplain peatlands used as sinks of raw municipal wastewater [28, 29], have demonstrated high efficiency of nitrogen and bacterial removal, whereas phosphorus adsorption and sedimentation decreases after 5-6 years, especially in winter [29]. The floodplain peatland of the Valgejõgi River by the small town of Tapa in northern Estonia, which has been heavily loaded by raw wastewater from the town and a distillery [28] for more than 25 years (from the early 1970s until 1997), was chosen for our study. Nowadays, a modern activated sludge system (Biolak) treats the wastewater, although mineral nitrogen and phosphorus concentrations in the outlet remain at an unacceptably high level. Therefore local water authorities plan to use part of the abandoned floodplain for the removal of nutrients from treated wastewater. The main objectives of this study are: (1) to analyze raw municipal wastewater treatment in the Valgejõgi River floodplain based on data from 1984-85, (2) to characterize the efficiency of the new sewage treatment plant of Tapa town, and (3) to study the treatment of effluents from the sewage treatment plant in an experimental plot established in the floodplain peatland.

Inflow

2

5

Flow direction

N

9

87

6

3 45

1

1110

30

25

20

15

10

5 10 15 20

m

m

Figure 1: Location of the wastewater treatment plant in Tapa, Estonia (left), and diagram of the test area in the Valgejõgi River floodplain (right). 1-11 – wells for water sampling and analyses.


434 Water Resources Management III

2 Materials and methods

2.1 Site description

The 300m wide floodplain of the River Valgejõgi (length 85 km, catchment area 453 km2) located by the small town Tapa in North Estonia (Fig. 1) has been used for 25 years as a sink for concentrated municipal wastewater (with effluents from a distillery in Moe village) with maximal discharge of 60,000 to 80,000 m3 d-1 [28]. Former floodplain meadows on alluvial and peatland soils have been abandoned since the 1950s and covered by willow bushes and sedge-dominated fen patches. Over an area of 18 ha affected by raw wastewater, large stands of willows, reed, and cattail have developed.

2.2 Experimental plot

A 21×31m quadrate was chosen within the floodplain’s western border, close to the outlet channel from the sewage treatment plant. The area had about a 1% slope to the north-northwest. Effluent from the treatment plant (~60 m3 d-1) was distributed using a 30mm PVC pipe perforated at the southern border of the plot (Fig. 1). Eleven 150 cm-long 50mm PVC tubes (piezometers) were installed in the plot area within the well-mineralized peat at a depth of 80cm, and the below-ground part was perforated and isolated with a water-permeable geomembrane to avoid clogging. During the whole experimental period from August to October 2002, no precipitation was observed, and the groundwater level in the peatland remained deeper than the piezometers. Therefore, water sampled in tubes was 100% of the filtrate of the sewage plant effluent.

2.3 Water sampling and analysis

During five sampling sessions from 19.08. – 14.10.2002, we measured the pH, temperature, conductivity, dissolved O2 and redox potential from piezometers installed in the floodplain study area (Fig. 1) using WTW MultiLine P4, WTW Oximeter 330, and Evikon portable equipment. We also measured the water table and took samples from piezometers and the inflow pipe for further analyses for BOD7, NH4-N, NO2-N, NO3-N, total N, PO4-P, total P, and total Fe (all according to APHA [30]) in the lab of Tartu Environmental Research Ltd. Water quality data on wastewater treatment efficiency in the floodplain in 1984-85 are gathered from Mander et al. [28]. Data on the purification efficiency of the Biolak sewage treatment plant originate from the local water supply company Tapa Vesi AS.

2.4 Calculations and statistical analysis

For data interpolation, the Kriging method is used. This is one of the most flexible interpolation methods, and is well suited to irregular data sets if there is also a need to extrapolate grid values beyond the collected data’s range. Kriging



with linear variogram model is found to represent best the measured values. All sampling points were taken into account to interpolate values within the experimental area. Floating boundary conditions (i.e. extrapolation) were allowed in calculation, while data lying outside the sampling area (21×31m) were truncated in the final data representation. The statistical analysis was carried out using Statistica 6.0 (StatSoft Inc.). The normality of variables was checked using the Lilliefors and Shapiro-Wilk tests. Among variables, NO3-N and total N were normally distributed, and other values have been normalized. We used the Wilcoxon Matched Pairs Test and the Mann-Whitney U-Test to check the significance between the water quality parameters. The Spearman Rank Order Correlation analysis of the relation between different parameters was performed. The level of significance α = 0.05 was accepted in all cases.

3 Results and discussion

3.1 Purification of raw wastewater in the floodplain in the 1980s and the performance of the new sewage treatment plant

The retention of organic matter (BOD5), mineral nitrogen, and total phosphorus during the vegetation period (May to October) in 1984 and 1985 was 96, 98, and 88% respectively, and in winter 56, 62, and 27% (Table 1; [28]).

Table 1: Purification of the raw wastewater from Tapa town and Moe distillery in the floodplain of the Valgejõgi River in October 1984 (upper row) and in March 1985 (lower row). 1 – BOD5; 2 – Total P; 3 – Total N; A – kg ha-1 d-1. Adopted from Mander et al. [28].

Inflow loading

(kg d-1)

Outflow loading

(kg d-1)

Removal in the floodplain

1 2 3 1 2 3 1 2 3

A % A % A %

540 16.2 41 21 0.3 5 113 96 3.5 98 8 88

380 25.9 59 160 9.7 43 48 58 3.5 63 4 27

Each hectare of this semi-natural wetland was able accumulate up to 1100 kg P and 2100 kg N yr-1. However, owing to the high initial concentrations in the effluent (on an average: BOD5 = 250 mg O2 l-1, N = 50 mg l-1 and P = 10 mg l-1), the Valgejõgi River was eutrophied (α-mesosaprobic) downstream. For instance, the concentration of NH4-N and Total P in river water significantly increased downstream from the wastewater inlet (Fig. 2).



02468

10121416

Upstream Down-stream


1984-1985 1997-2001

BOD

5 & N

O3-

N (m

g l-1

)

BOD5 NO3-N

**

0,0

0,2

0,4

0,6

0,8

1,0



1984-1985 1997-2001

Tota

l P &

NH

4-N

(mg

l-1)

0,000,100,200,300,400,500,60

NO

2-N

(mg

l-1)

Total P NH4-N NO2-N

**

*

*3,75+/-3.07

**

Figure 2: Change of water quality in the Valgejõgi River upstream and downstream from Tapa town before (1984-1985) and after the establishment of the sewage treatment plant (1997-2001). * - significantly differing value (p <0.05) according to the Wilcoxon Matched Pairs Test.

BOD7

1

10

100

1000

1997 1998 1999 2000 2001 2002

BO

D7 (

mg

O2 l

-1)

Average inflow Max inflow Average outflow Max outflow

Suspended solids

1

10

100

1000

10000

1997 1998 1999 2000 2001 2002

Susp

ende

d so

lids (

mg

l-1)


Total N

0

20

40

60

80

100

1997 1998 1999 2000 2001 2002

Tot

al N

(mg

l-1)


Total P

0

5

10

15

20

25

1997 1998 1999 2000 2001 2002

Tota

l P (m

g l-1

)


Water discharge

010002000300040005000

1997 1998 1999 2000 2001 2002

Q (m

3 h-1

)

Dry average Dry maxWet max Wet average

standard (2 mg P l-1)

Figure 3: Performance of the Tapa Biolak wastewater treatment plant in 1997-2002.

The establishment of a sewage treatment plant (Biolak) in 1997 resulted in a significant decrease in ammonia nitrogen in the river water downstream from Tapa (Fig. 2). Also, the BOD5 level decreased in the river water. However, the purification results are not satisfactory regarding Total P, showing higher



concentrations (5 mg l-1 on an average) in the outflow than the standards for sensitive water bodies (2 mg l-1). There are two possible reasons for the lowered P retention capacity. First, the inlet P values have been increasing overloading on the sewage system’s capacity, and second, water discharge varied too much, causing the collapse of the activated sludge community (Fig. 3). Likewise, the Total N inlet concentrations have been increasing, which might be related, as in the case of P, to a lower consumption of water by inhabitants. Due to higher loading, the outlet Total N and NO3-N concentrations (sometimes <20 mg l-1) remain higher than acceptable for sensitive water courses. The BOD5 value and suspended solids concentration show a satisfactory decrease (Fig. 3). Owing to all these factors, there is both a need and an opportunity to use the peatland area for additional nutrient removal.

3.2 Purification of the sewage plant effluent in the experimental plot

We observed a significant decrease in Total P concentration during all 5 sampling sessions: from 12-13 to 0.2-1.8 mg l (68-75%; Fig. 4).

0 5 10 15 200

5

10

15

20

25

3019.08.2002

0 5 10 15 200

5

10

15

20

25

3006.09.2002

0 5 10 15 200

5

10

15

20

25

3016.09.2002

0 5 10 15 200

5

10

15

20

25

3014.10.2002

0 5 10 15 200

5

10

15

20

25

3030.09.2002

0 5 10 15 200

5

10

15

20

25

30

Period mean19.08.2002-14.10.2002

m m m

m mmmm

m

mmm

0 2.5 5 7.5 10 12.5 15mg/l

Figure 4: Distribution of total P concentrations in the pilot area.



0 5 10 15 200

5

10

15

20

25

30 19.08.2002

0 5 10 15 200

5

10

15

20

25

3006.09.2002

0 5 10 15 200

5

10

15

20

25

3016.09.2002

0 5 10 15 200

5

10

15

20

25

3030.09.2002

0 5 10 15 200

5

10

15

20

25

30

Period mean19.08.2002-14.10.20020

5

10

15

20

25

30

mg/l35

m m m

m mmm

m

mm Figure 5: Distribution of NO3-N concentrations in the pilot area.

0 5 10 15 200

5

10

15

20

25

30 19.08.2002

0 5 10 15 200

5

10

15

20

25

3006.09.2002

0 5 10 15 200

5

10

15

20

25

3016.09.2002

0 5 10 15 200

5

10

15

20

25

30

0 5 10 15 200

5

10

15

20

25

3030.09.2002

Period mean19.06.2002-14.10.20020

5

10

15

20

25

30

35mg/l

m m m

m mmm

m

mm

Figure 6: Distribution of Total N concentrations in the pilot area.



0 5 10 15 200

5

10

15

20

25

30

16.09.2002

0 5 10 15 200

5

10

15

20

25

30

19.08.20020 5 10 15 200

5

10

15

20

25

30

06.09.2002 16.09.2002

0 5 10 15 200

5

10

15

20

25

30

30.09.20020 5 10 15 200

5

10

15

20

25

30

Period mean19.08.2002-14.10.2002

m m m

mmmm m

0

0.25

0.5

0.75

1

1.25

1.5

1.75

2

2.25mg/l

Figure 7: Distribution of NH4-N concentrations in the pilot area.

According to our expectations, the NO3-N concentrations decreased significantly in the experimental plot, varying from 34 to 1.5 mg l-1. The average decrease in nitrate concentration was between 50-85% (Fig. 5). Likewise, due to the high mineralization rate of nutrients in the effluent, the Total N concentration shows changes similar to the NO3-N pattern, decreasing about 25-30% (Fig. 6). As assumed, the NH4-N concentration in piezometers increased slightly along the distance from the inflow pipe (Fig. 7). This is related to the low ammonia concentrations in the treatment plant effluent and the both temporary and micro-spatially less aerated conditions in the peatland area.

Table 2: Spearman Rank Order Correlation (Rs) values and their significance level (α) between the water quality parameters and the distance (in meters) from the inflow pipe. 1 - NO3, 2 - Total N, 3 - NH4, 4 - NO2, 5 - PO4, 6 - Total P, 7 - Total Fe; * - significant; ** - strongly significant.

1 2 3 4 5 6 7 RS -0.34* -0.34* 0.30* -0.084 -0.436* -0.44* 0.62** α 0.035 0.020 0.041 0.625 0.010 0.006 0.0005

The BOD7 value showed no regular distribution pattern, however, in most of the sampling sessions, and its value increased slightly in the distal part of the



sampling plot. This is apparently caused by the low concentration of organic material in the treatment plant effluent. Results of the efficiency of treatment plant effluent purification in our experimental plot, presented as distribution maps (Figs. 4-7), are supported by the Spearman Rank Order Correlation (Rs) analysis. As seen in Table 2, the concentration of NO3-N, Total N, PO4-P, and Total P significantly decreases with increasing distance from the inlet pipe. In contrast, the concentration of NH4-N and total Fe increased significantly with increasing distance from the inflow site (Table 2). Less aerated microsites within a generally well-aerated peat column would be the reason for this.

Table 3: Spearman Rank Order Correlation of water quality characteristics. 1 - NO3, 2 - Total N, 3 - redox potential, 4 - conductivity, 5 - NH4, 6 - NO2, 7 - PO4, 8 - Total P, 9 - Total Fe; * - α <0.05; ** - α <0.001.

1 2 3 4 5 6 7 8 9 1 1.00 0.85** 0.24 0.14 0.56* 0.14 0.56* 0.54* -0.27 2 1.00 0.42* 0.10 0.48* 0.02 0.31 0.23 -0.10 3 1.00 0.17 0.28 0.25 0.06 0.08 -0.41* 4 1.00 0.18 0.32 0.32 0.32 -0.16 5 1.00 0.59* -0.52* -0.51* 0.49* 6 1.00 -0.38* -0.38* 0.24 7 1.00 0.99** -0.42* 8 1.00 -0.45* 9 1.00

Correlation analysis yielded largely expectable results. For instance, the Spearman Rank Order Correlation between Total N and NO3-N was highly significant (Rs = 0.85, Table 3). Likewise, the Total N and NH4-N shows that the share of organic N in the effluent is relatively small. Satisfactory mineralization of organic material is also demonstrated by significant correlations between NO3-N and NH4-N (Rs = 0.56), NO3-N and PO4-P (Rs = 0.56), and Total P and PO4-P (Rs = 0.99) concentrations. Lower values for redox potential are significantly correlated with higher Total Fe concentrations (Rs = -0.41), and higher Total Fe concentrations are positively correlated with lower PO4-P concentrations (Rs = -0.42). Both relationships are related to the variability of anaerobic and aerobic conditions within the peatland. Water temperature fell significantly during the sampling period, and also with increasing distance from the inflow site: from 18 to 15.7 oC on August 16th and from 9 to 4.9 oC on October 14th. The pH value varied from 6.9 to 7.4, showing no regular pattern in either the temporal or spatial scale. The potential redox value in piezometers was between 448 and -20 mV, showing a significant decrease with increasing distance from the inflow pipe. It varied significantly between the sampling events, being highest (from 448 to 148 mV) on October 14th and lowest (from 75 to 2 mV) on September 16th. Conductivity varied from 1139 to 848 µS cm-1, showing lower values at the distal part of the experimental plot.



Other short-term investigations on peatland filters show similar high Total P and Total N removal capacity [23]. However, long-term investigations show lower Total P and Total N removal capacity. For instance, in-ground intermittent peat filters with gravity distribution in southern Minnesota reduced the BOD5 level by 99%, removed 98% of solid substances, >99.99% of fecal coliform bacteria, but only 42% of Total p and 17% of Total N [24]. Another peatland filter treating effluents from a wastewater stabilization lagoon in Drummond, Wisconsin, removed 17% of the phosphorus and 37% of the nitrogen remaining in the lagoon effluent. Moreover, the peatland’s capacity to retain phosphorus was exhausted after a few years of use [27]. Our experience, however, showed that after a 4-5 year relaxing period, retention capacity can be rehabilitated, as happened in the Valgejõgi River floodplain. Likewise, Finnish experiences show that 37-68% of Total P and 38-74% of total N has been removed in overland flow peatlands treating peat mining effluents over more than 20 years [19, 20, 22]. Regarding phosphorus retention, most of the mineral P is retained in the peat matrix, governed by aluminium and iron phosphate formation [21, 22]. Knowledge of the role of plant uptake and microbial immobilization in peatlands is still very weak [22].

4 Conclusions

Our short-term investigations show that semi-natural floodplain communities on well-mineralized peat can be effective filter system to remove phosphorus and nitrate nitrogen from secondary treated municipal wastewater. In our experiments, removal of Total N and Total P was 25-30% and 68-75% respectively, and reduction of NO3-N concentrations was about 50-85%. According to the average recommendable hydraulic load of 0.15 m d-1 and generally acceptable calculation formulae [18], a 2.0 ha floodplain peatland area would be necessary to treat the effluent to the Total P level 1 mg l-1 which is required by a new standard for sensitive and ecologically valuable water bodies. More experiments, however, are necessary to decide on the long-term capacity of floodplain peatlands to remove nutrients.

Acknowledgements

This study was supported by EU 5 FP RTD project PRIMROSE (EVK1-2000-00728) “PRocess Based Integrated Management of Constructed and Riverine Wetlands for Optimal Control of Wastewater at Catchment ScalE”, Estonian Science Foundation grants Nos. 5247 and 6056, and Target Funding Project No. 0182534s03 of the Ministry of Education and Science, Estonia. The authors would like to thank C. Vohla, E. Põldvere, A. Tooming, A. Noorvee, M. Maddison and K. Soosaar, students at the University of Tartu, for their help with the field studies.



References

[1] McKay, G. Peat – an adsorbent-filtration medium for wastewater-treatment. Water Serv., 84(1012), pp. 357-359, 1980.

[2] Rock, C.A., Brooks, J.L., Bradeen, S.A. & Struchtmeyer, R.A. Use of peat for on-site wastewater-treatment. 1. Laboratory evaluation. J. Environ. Qual., 13(4), pp. 518-523, 1984.

[3] Brooks, J.L., Rock, C.A. & Struchtmeyer, R.A. Use of peat for on-site wastewater-treatment. 2. Field studies. J. Environ. Qual., 13(4), pp. 524-530, 1984.

[4] Couillard, D. Appropriate waste-water management technologies using peat. J. Environ. Syst., 21(1), pp. 1-20, 1992.

[5] Viraraghavan, T. Peat-based onsite waste-water systems. J. Environ. Sci. Heal. A, 28(1), pp. 1-10, 1993.

[6] Couillard, D. The use of peat in wastewater treatment. Water Res., 28(6), pp. 1261-1274, 1994.

[7] Lens, P.N., Vochten, P.M., Speelers, L. & Verstraete, W.H. Direct treatment of domestic waste-water by percolation over peat, bark and woodchips. Water. Res., 28(1), pp. 17-26, 1994.

[8] White, K.D., Byrd, L.A., Robertson, S.C., O’Driscoll, J.P. & King, T. Evaluation of peat biofilters for onsite sewage management. J. Environ. Health, 58(4), pp. 11-17, 1995.

[9] Gunes, K. & Ayaz, S.C. Wastewater treatment by peat filtration. Fresen. Environ. Bull., 7(9A-10A), pp. 777-782, Sp.iss. SI, 1998.

[10] Talbot, P., Bélanger, G., Pelletier, M., Laliberté, G. & Arcand, Y. Development of a biofilter using an organic medium for on-site wastewater treatment. Water Sci. Technol., 34(3-4), pp. 435-441, 1996.

[11] Pundsack, J., Axler, R., Hicks, R., Henneck, J., Nordman, D. & McCarthy, B. Seasonal pathogen removal by alternative on-site wastewater treatment systems. Water Environ. Res., 73(2), pp. 204-212, 2001.

[12] James, B.R., Rabenhorst, M.C. & Frigon, G.A. Phosphorus sorption by peat and sand amended with iron-oxides or steel wool. Water Environ. Res., 64(5), pp. 699-705, 1992.

[13] Roberge, G., Blais, J.F. & Mercier, G. Phosphorus removal from wastewater treated with red mud-doped peat. Can. J. Chem. Eng., 77(6), pp, 1185-1194, 1999.

[14] McLellan, J.K. & Rock, C.A. Pretreating landfill leachate with peat to remove metals. Water Air Soil Poll., 37, pp. 203-215, 1988.

[15] Davila, J.S., Matos, C.M. & Calcavanti, M.R. Heavy-metals removal from waste-water using activated peat. Water Sci. Technol., 26(9-11), pp. 2309-2312, 1992.

[16] Brown, P.A., Gill, S.A. & Allen, S.J. Metal removal from wastewater using peat. Water. Res., 34(16), pp. 3907-3916, 2000.

[17] Kennedy, P.L. & Van Geel, P.J. Impact of density on the hydraulics of peat filters. Can. J. Geotech., 38(6), pp. 1213-1219, 2001.



[18] Kadlec, R.H. & Knight, R.L. Treatment Wetlands, CRC Lewis Publishers: New York, 893 p., 1996.

[19] Heikkinen, K., Ihme, R. & Lakso, E. Contribution of cation exchange property of overflow wetland peat to removal of NH4

+ discharged from some Finnish peat mines. Appl. Geochem., 10(2), pp. 207-214, 1995.

[20] Heikkinen, K., Ihme, R., Osma, A.M. & Hartikainen, H. Phosphate removal by peat from peat mining drainage waterduring overland flow wetland treatment. J. Environ. Qual., 24(4), pp. 597-602, 1995.

[21] Nieminen, M. & Jarva, M. Phosphorus adsorption by peat by drained mires in southern Finland. Scand. J. Forest Res., 11, pp. 321-326, 1996.

[22] Silvan, N. Nutrient Retention in a Restored Peatland Buffer. Academic Dissertation. University of Helsinki Department of Forest Ecology Publications 32, 2004.

[23] Dubuc, Y., Jannetau, P., Labonte, R., Roy, C. & Briere, F. Domestic wastewater treatment by peatlands in a northern climate: a water quality study. Water Resour. Bull., 22, pp. 297-303, 1986.

[24] Monson Geerts, S.D., McCarthy, B, Axler, R., Henneck, J., Heger Christopherson, S., Crosby, J. & Guite, M. Performance of peat filters in the treatment of domestic wastewater in Minnesota. 9th National Symposium on Individual and Small Community Sewage Systems, Fort Worth, TX, March 11-14, 2001. Amer. Society of Agricultural Engineers, St. Joseph, Michigan. 49085-9659 USA, 2001.

[25] Premier Tech Environment. PeatlandTM. 2004. www.premiertech.com /ecoflo/biofilter/wastewater/peatland/peatland.htm

[26] Kinsley, C.B., Crolla, A.M., Kuyucak, N., Zimmer, M. & Laflèche, A. A pilot peat filter & constructed wetland system treating landfill leachate. 9th International Conference on Wetland Systems for Water Pollution Control, Avignon (France), 26-30th of September 2004, Cemagref, Antony, pp. 635-642, 2004.

[27] Nichols, D.S. & Higgins, D.A. Long-term wastewater treatment effectiveness of a northern Wisconsin peatland. J. Environ. Qual., 29(5), pp. 1703-1714, 2000.

[28] Mander, Ü., Matt, O. & Nugin, U. Perspectives on vegetated shoals, ponds and outdoor systems of wastewater treatment in Estonia. Ecological Engineering for Wastewater Treatment, eds. C. Etnier & B. Guterstam. CRC/Lewis, New York, pp. 251-262, 1997.

[29] Nõges, P & Järvet, A. Response of a natural river valley wetland to supplementary runoff and pollutant load from urban wastewater discharge. Natural Wetlands for Wastewater Treatment in Cold Climates, Advances in Ecological Sciences 12, eds. Ü. Mander & P.D. Jenssen, WIT Press, Southampton, Boston, pp. 177-188, 2002.

[30] APHA. Standard Methods for the Examination of Water and Waste Water. American Public Health Organisation, 18th edition, Washington, D.C., 1992.



Tertiary treatment of municipal wastewater in a floodplain ... · Tertiary treatment of municipal...

Documents

Transcript of Tertiary treatment of municipal wastewater in a floodplain ... · Tertiary treatment of municipal...