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e c o l o g i c a l e n g i n e e r i n g 3 2 ( 2 0 0 7 ) 1–10
avai lab le at www.sc iencedi rec t .com
journa l homepage: www.e lsev ier .com/ locate /eco leng
mproving multi-soil-layer (MSL) systememediation of dairy effluent
. Pattnaika, R.S. Yosta,∗, G. Portera, T. Masunagab, T. Attanandanac
Department of Tropical Plant and Soil Sciences, University of Hawai‘i, 3190 Maile Way, 102 St. John, Hawaii 96822, USAFaculty of Life and Environmental Science, Shimane University, Matsue 690-8504, JapanDepartment of Soil Science, Faculty of Agriculture, Kasetsart University, Jatujak, Bangkok 10900, Thailand
r t i c l e i n f o
rticle history:
eceived 23 December 2006
eceived in revised form 5 July 2007
ccepted 16 August 2007
eywords:
airy effluent
airy wastewater treatment
ulti-soil-layer system
oil dynamics
ropical soils
a b s t r a c t
Dairy effluent disposal is a serious problem in the Hawaiian Islands. Dairies often estab-
lish multiple settling lagoons to accumulate and store effluent. Occasionally, the overflow
of lagoons leads to the transfer of nutrients, such as nitrogen (N) and phosphorus (P), and
other contaminants, to hydrologically associated surface, subsurface, and coastal waters.
This study was conducted to assess the removal of inorganic N and phosphate in dairy
effluent using multi-soil-layer (MSL) systems. Four MSL systems were constructed with two
replications of two treatments, which were Perlite and the Leilehua soil. Both materials were
used separately for forming an aerobic layer in the MSL systems, whereas an anaerobic layer
was formed from a mixture of charcoal, sawdust, iron filings and Honouliuli soil. The results
of this study revealed that the removal of inorganic N was similar for the Leilehua and Perlite
MSL system, which was 22–93% and 21–96%, respectively. Phosphate removal was higher
in the Leilehua MSL system (64–99%) compared to the Perlite MSL system (9–97%). Addi-
norganic nitrogen removal
ffectiveness
hosphate removal effectiveness
tional aeration increased the removal of phosphate by the Leilehua MSL system. Sucrose
application with a constant rate of aeration increased the removal of inorganic N both
in the Leilehua and Perlite MSL systems and increased phosphate removal in the Perlite
MSL system. The study demonstrated that MSL systems have the potential to remove high
percentages of inorganic N and phosphate in dairy effluent enabling reuse of the water.
to accumulate and store effluent. Occasionally, the lagoons
. Introduction
he dairy industry generates wastewaters characterized byigh concentrations of nutrients, organic contents, andathogens (USDA-SCS, 1992). The organic and nutrient con-ent of dairy wastewaters depends upon the size, lactation,nd diet of the cow. In addition, dairy wastewater compositions significantly influenced by the wastewater management,
limate, operating conditions, and types of flushing. Table 1hows the levels of major nutrients in dairy wastewater. Theairy industry is one of the major sources of waste efflu-∗ Corresponding author. Tel.: +1 808 956 7066; fax: +1 808 956 3894.E-mail address: [email protected] (R.S. Yost).
925-8574/$ – see front matter © 2007 Elsevier B.V. All rights reserved.oi:10.1016/j.ecoleng.2007.08.006
© 2007 Elsevier B.V. All rights reserved.
ents in Hawaii and in the Continental U.S. (USDA-SCS, 1992).Dairy effluent disposal is a serious problem in Hawaii andother Pacific Islands (Farrell-Poe, personal communication,2007). The problem is due to the confined aquifers and lim-ited availability of water in Pacific Island environments. Thecurrent method used in Hawaii to dispose dairy effluent islarge settling lagoons. Dairies often establish multiple lagoons
overflow, leading to the transfer of nutrients, such as nitro-gen (N) and phosphorus (P), and other contaminants, whichcan pollute surface, subsurface, and coastal waters. Effluents
2 e c o l o g i c a l e n g i n e e r i n g 3 2 ( 2 0 0 7 ) 1–10
Table 1 – Dairy wastewater characteristics (Wright, 1996)
Potential pollutantsource
Biochemical oxygendemand (mg L−1)
Nitrogen(mg kg−1)
Phosphorus(mg kg−1)
Volume gallons(100 cows y−1)
Milking center waste 400–10,000 80–900 25–170 73,000Silage leachate 12,000–90,000 4400 500 105,000
Barnyard runoff 1000–10,000Dairy manure 20,000high in N and P concentration can cause eutrophication ofthe receiving waters, degrading water quality (Smith et al.,1999). The Environmental Protection Agency (EPA) and StateDepartment of Health (DOH) have rules and regulations forthe disposal of dairy effluent (Hawaii State Department ofHealth Wastewater Branch, 1996). Proper management of dairyeffluent is currently a serious problem in Hawaii, which hasincreased the operation costs and reduced profitability ofmany island dairies. The inability of many dairy operatorsto properly manage the effluent has forced more than 50%of them to close during the last 10 years (C.N. Lee, personalcommunication, 2006).
With rising environmental concerns and tighter gov-ernmental regulations, managing animal wastes in anenvironmentally responsible and economically feasible waycan be a challenge. It is becoming imperative that new waysof waste treatment be found that reduce excessive nutri-ents from dairy effluent and yet are efficient and reliable.Some of the methods of dairy waste treatment include landapplication (Caro-Costas et al., 1972; Valencia-Gica et al.,2004), vegetative filter strips (Ikenberry and Mankin, 2000),constructed wetlands (Schaafsma et al., 2000), aerobic andanaerobic processes (Manariotis and Grigoropoulos, 2003), andbioremediation (Prochaska and Zouboulis, 2003) which haveperformed well, but their widespread use is limited becausethey are either costly, require regular maintenance, requirelarge areas of land, or the wastewater must be pre-treated. Themulti-soil-layer (MSL) system is a promising alternative withpotential for reducing contamination associated with dairyeffluent.
The MSL system is a technology that uses natural soil ina unit to facilitate wastewater treatment (Wakatsuki et al.,1993). This has been successfully developed in Japan and Thai-land to treat domestic and restaurant wastewater as well as
polluted river water (Wakatsuki et al., 1993; Luanmanee etal., 2001). The system reduces levels of inorganic contami-nants such as nitrate, ammonium, and phosphate, as wellTable 2 – Selected physical properties of Leilehua and Honouliu
Series Clay (<0.002)(% of <2 mmmineral soil)
Silt (0.002–0.05)(% of <2 mmmineral soil)
Sand (0.05–2)(% of <2 mmmineral soil)
Leilehua 58.5 33.6 7.9Honouliuli 58.4 34.8 6.8
Source: Soil Survey Staff (2006).
50–2500 5–500 80,0005600 900 660,000
as organic contaminants as measured by high COD (chem-ical oxygen demand) and BOD (biological oxygen demand).This is a biphasic layered system that uses locally availablematerials such as soil, iron particles, jute or sawdust, char-coal, and zeolite or alternative materials (Attanandana et al.,2000; Luanmanee et al., 2001). Two layers that comprise MSLsystems are aerobic and anaerobic. Aerobic layers consist ofzeolite or Perlite alternated with anaerobic layers of soil mix-ture blocks. The efficiency of the MSL system in purifyingwastewater depends on the relative effectiveness of aerobicand anaerobic layers (Wakatsuki et al., 1993; Attanandana etal., 2000). The aerobic layer enhances nitrification, oxidationand precipitation of mobile ferrous iron to high-surface areaferric oxide, enhancing phosphorus sorption (Wakatsuki et al.,1993). In the anaerobic layer of the soil mixture block, nitrateis transformed into nitrous oxide and nitrogen gas (denitri-fied) and ferric iron is reduced to the more mobile ferrousiron, which moves out of the anaerobic layer (Wakatsuki etal., 1993). Although an appropriate amount and timing of aer-ation is necessary (Luanmanee et al., 2002), the maintenanceof an MSL system is simple and the effective life of such sys-tems was estimated to be longer than 10 years (Luanmanee etal., 2002).
Although various types of wastewater treatments havebeen treated successfully using the MSL system in Japan andThailand, to-date, no MSL system has been tested or adaptedfor the remediation of dairy effluent. In addition, there isnot much information available on the reliability, consistency,and nutrient removal efficiency of MSL systems. Thus, it is ofinterest to determine whether the MSL system can remedi-ate dairy effluent. This study was conducted to (a) investigatethe potential of the MSL systems in remediating dairy efflu-ent, (b) compare the removal of inorganic N and phosphate,between MSL systems with the aerobic layers made from
Leilehua soil or Perlite, and (c) evaluate the effect of aerationand sucrose additions on inorganic N and phosphate removalefficiency.li soils
Water holdingcapacity (% of <2 mm
mineral soil)
Bulk density(g cm−3)
Particledensity(g cm−3)
33 kPa 1500 kPa
n/a 33.2 0.97 2.8830.2 22.3 1.31 2.93
e r i n
2
2
TlHoSdwselulsCtg
2
CshwsPpAua((sfitmpahAb
e c o l o g i c a l e n g i n e
. Materials and methods
.1. Experimental site and design
he experimental site was located in Waianae, latitude 21◦27′,ongitude 158◦11′ on the west shore of the island of O’ahu,awaii. Average maximum and minimum daily temperaturesf the area are 28 ◦C (83◦ F) and 16 ◦C (61◦ F) (Hobo Weathertation, 2001–2003). The experiment was conducted usingairy effluent from the third settling lagoon of an effluentaste management system. Four MSL systems were con-
tructed, comprising two treatments with two replicationsach, arranged in a completely randomized design (CRD). Per-ite or Leilehua soil (A horizon, Typic Kanhaplohumult) wassed for the aerobic layer in the two treatments. The anaerobic
ayer for both treatments consisted of a mixture of charcoal,awdust, iron filings and the Honouliuli soil (A horizon, Typichromustert). The physical and chemical properties of both
he Leilehua and Honouliuli soils used for the experiment areiven in Tables 2 and 3.
.2. MSL systems and operations
ross-section composition of the overall MSL systems is pre-ented in Fig. 1. Each of the MSL system consisted of aigh-density polyethylene (HDPE) corrugated sewage pipeith 45.7 cm interior diameter by 1 m in height with a cross-
ectional area of approximately 0.1648 m2 (Fig. 1). A 25.4 mmVC pipe was installed at the base of each of the upright HDPEipe to discharge the MSL treated effluent from the system.
layer of gravel (≈5 cm) was placed at the bottom of thepright pipes to facilitate system discharge. Each system wasssembled from seven alternating layers of soil mixture blocksanaerobic layers) and eight layers of Leilehua soil or Perliteaerobic layers) (Fig. 1). Each of the soil mixture blocks con-isted of Honouliuli soil mixed with finely ground charcoal,ne sawdust, and approximately 1 mm diameter iron filings athe ratio of 7:1:1:1 by dry weight. The soil mixture was evenly
ixed using an concrete mixer and packed into two sizes ofre-stitched burlap bags, approximately 5 cm × 10 cm × 22 cm
nd 5 cm × 10 cm × 38 cm. The particle sizes of both the Leile-ua soil and the Perlite filler were less than or equal to 4 mm.n aeration pipe was installed approximately 50 cm from theottom for the subsequent infusion of air whenever it was nec-Table 3 – Chemical properties of Leilehua and Honouliuli soils
Soil pH(H2O, 1:1)
OCa (% of<2 mm)
TNb (%<2 mm
Leilehua 4.8 2.61 0.233Honouliuli 6.9 0.74 0.11
Source: Soil Survey Staff (2006).a Organic carbon.b Total nitrogen.c Dithionite-citrate extractable iron.d Ammonium oxalate iron.e Guo and Yost (1998).
g 3 2 ( 2 0 0 7 ) 1–10 3
essary (Fig. 1). An array of effluent emitters was installed onthe top (≈80 cm from the bottom) of the aerobic and anaer-obic layers through which the dairy effluent was dischargedinto the system (Fig. 1).
2.2.1. Application ratesThe dairy effluent was directly pumped from the lagoon, fil-tered using a 0.0254 m plastic disc filter (140 mesh) to removethe larger particles, and discharged into the MSL system.Three application rates of effluent were applied to the sys-tem according to the performance of the system. An initialflow rate of 80 L day−1 (505 L m−2 day−1) was applied to eachof the system from 18 April to 3 November 2005. Effluentwas applied through drip irrigation emitters during approx-imately 20 h day−1. The flow rate was reduced to 40 L day−1
(252 L m−2 day−1) on 3 November 2005 and continued until 20April 2006. Then from 20 April to 10 July 2006 the flow rate wasagain reduced to 28 L day−1 (178 L m−2 day−1).
2.2.2. Aeration ratesDifferent aeration rates were applied to the systems. Aera-tion was not applied to the systems until the 10th month ofthe study. The systems were aerated at a rate of 28 L min−1
from 10 February to 13 April 2006. The aeration was increasedto 31 L min−1 from 14 to 27 April 2006. The aeration rate wasdecreased to 17 L min−1 for 1 week, from 28 April to 4 May 2006followed by a rate of 11 L min−1 until 18 May 2006. The aera-tion rate was increased again to 23 L min−1 from 19 May until10 July 2006.
2.2.3. Sucrose additionsAn additional source of carbon in the form of a sucrose solu-tion was applied to the MSL system beginning at the endof the 12th month of the study in attempt to improve sys-tem performance. The sucrose solution was calculated basedon the amounts needed for a stoichiometric reduction of theexpected oxygen content of the MSL system.
The percent pore space was calculated first from the bulkdensities and particle densities of Leilehua and Honouliuli soil,and Perlite. Then the amount of air space was calculated fromthe volume of each system. The amount of oxygen was calcu-
lated from the amount of air space and the amount of oxygenin the air. The amount of sucrose was calculated based onthe stoichiometric reaction equation, which shows how muchsucrose is needed for the microorganisms to consume the spe-of)
Dithionitec
(% of <2 mm)Oxalated (% of
<2 mm)P sorbede
(mg kg−1)
6.4 1.04 14007.5 n/a 100
4 e c o l o g i c a l e n g i n e e r i n g 3 2 ( 2 0 0 7 ) 1–10
SL s
Fig. 1 – Cross-sections of the Mcific amount of oxygen:
C12H22O11 + 12O2 → 12CO2 + 11H2O
Finally, the application of sucrose was made as a solutionmixed with the incoming effluent and applied based on theeffluent retention time of the MSL systems.
ystems (Leilehua and Perlite).
The calculated concentration of sucrose solution was 19 g(0.055 moles per 500 mL) for the Leilehua system and 22 g(0.064 moles 500 mL) for the Perlite system.
2.3. Analytical methods
Samples were taken every week except during the periodDecember 2005 to 14 January 2006. After filtering samples
e c o l o g i c a l e n g i n e e r i n g 3 2 ( 2 0 0 7 ) 1–10 5
Table 4 – Dairy effluent used in this experiment, in comparison with data from other dairy lagoons in Hawaii
Source pH EC(mS cm−1)
TSS(mg L−1)
TN(�g mL−1)
NH4+-N
(�g mL−1)NO3
−-N(�g mL−1)
TP(�g mL−1)
IP(�g mL−1)
COD(mg L−1)
Dairy aa 8.2 6.4 n/a 395.7 183.8 n/a 14.5 n/a n/aDairy bb 8.1 3.0 ∼1000 119 108 5.76 16.8 n/a n/aThis experimentc 8.4 3.6 400 44.6 43.16 1.30 21.39 13.21 482This experimentd 7.77 3.22 n/a 20 17.05 2.86 17.76 5.72 447This experimente 8.90 3.62 320 5.39f 5.26 0.12 NA 6.08 710
EC: electrical conductivity; TSS: total suspended solid; TN: total nitrogen; TP: total phosphorus; IP: inorganic phosphate; COD: chemical oxygendemand.a Analysis of lagoon effluents from various nutrient streams (Fukumoto et al., 2000).b Valencia-Gica et al. (2004).c One month before running the experiment, 3 March 2005.
wnn(cnTam1
2
TbpswPm2
3
TdMsJsDbDdutoi
((
October) (Figs. 2 and 3).The MSL systems were not significantly different in per-
centage removal of inorganic N (P > 0.1) (Table 5). However,the percentage removal of inorganic N was significantly differ-
d The beginning of the experiment, 2 May 2005.e The end of the experiment, 10 July 2006.f Total inorganic N (summation of NH4
+-N and NO3−-N).
ere analyzed for the following: ammonia nitrogen (NH4+-N),
itrate nitrogen (NO3−-N), and inorganic phosphate. Ammo-
ia nitrogen was measured using the salicylate methodMulvaney, 1996a). Nitrate nitrogen was measured using theadmium reduction method (Mulvaney, 1996b). Total effluentitrogen consisted of 98% ammonium and about 1% nitrate.he total inorganic nitrogen (Inorganic N) was approximateds the summation of NH4
+-N and NO3−-N. The ascorbic acid
ethod was used to measure total inorganic phosphate (Kuo,996).
.4. Statistical analysis
he percentage removal of inorganic N and phosphateetween the Leilehua and Perlite MSL systems were com-ared using Sigma Plot version 9 (Sigma Plot, 2004). Data forelected intervals of time corresponding to specific treatmentsere also analyzed using the Statistical Analysis Software, SASROC MIXED Repeated Measures ANOVA and Least Squareeans (LSmeans) (SAS, 2004) (Littell et al., 1996, 1998; SAS,
004).
. Results
he percentage removal of inorganic N and phosphate areiscussed in two phases. The first phase data occurred fromay to October 2005, when the system was operated at con-
tant conditions and the second phase data from January touly 2006, where specific treatments were applied. Althoughamples were collected in the first phase from October toecember 2005, the data were not included in the analysisecause of system malfunction. There was a 6-week pause (2ecember 2005 to 14 January 2006) between the two phasesue to mechanical problems and also due to a suspected buildp of biofilms. In the second phase aeration and sucrose addi-ions were compared in an attempt to increase the efficiencyf the MSL systems. Three possible improvements were tested
n the second phase:
1) effect of increased aeration,2) effect of sucrose addition with a constant rate of aeration,
and
(3) the combination of these two improvements.
3.1. Characteristics of dairy effluent
The analysis of the effluent was compared with other dairyeffluents in Hawaii (Fukumoto et al., 2000; Valencia-Gica etal., 2004) (Table 4). The concentration of total N, NH4
+-N, andNO3
−-N was lower in the effluent use in this experiment thanthe other dairy effluent. This might be a result of using effluentfrom the third and last settling of the lagoon system, whichwas more diluted than that from the first lagoon.
3.2. First phase (year 2005)
The effectiveness of the MSL systems in removing inorganic Nand phosphate was compared over a 6-month period (5 May–5
Fig. 2 – Removal of inorganic N in the Leilehua and PerliteMSL systems as affected by time. In this figure “2D”indicates a 2-day pause; “3D” a 3-day pause; “6D” a 6-daypause; “8D” a 8-day pause; “12D” a 12-day pause.
6 e c o l o g i c a l e n g i n e e r i n g 3 2 ( 2 0 0 7 ) 1–10
Fig. 3 – Removal of phosphate in the Leilehua and PerliteMSL systems as affected by time. In this figure “2D”indicates a 2-day pause; “3D” a 3-day pause; “6D” a 6-daypause; “8D” a 8-day pause; “12D” a 12-day pause.
Table 5 – A comparison of the effect of time and MSLsystem on inorganic N removal as analyzed by SAS ProcMixed repeated measures analysis
Factor Probability of significance (P)
Fig. 4 – Removal of inorganic N in the Leilehua and Perlite
inorganic N (P > 0.1) (Table 7). The removal of inorganic N by theLeilehua system and the Perlite system ranged from 8 to 61%(LSmean of 29.34) and 10 to 73% (LSmean of 33.10), respectively(Fig. 4).
MSL systems 0.8303Time <0.0001MSL systems × time 0.9474
ent over time for both the MSL systems (P < 0.0001) (Table 5).The non-significant interaction indicates that the MSL sys-tems behaved similarly in percentage removal of inorganicN (P > 0.1) (Table 5). The inorganic N removal by the LeilehuaMSL system and the Perlite MSL system ranged from 22 to 93%(LSmean of 61.94) and 21 to 96% (LSmean of 63.40), respectively(Fig. 2).
The percentage removal of phosphate was significantly dif-ferent by both the MSL systems (P < 0.05) (Table 6). The LeilehuaMSL system was more effective in removing phosphate thanthe Perlite MSL system. There was also a significant differ-ence in percentage removal of phosphate over time (P < 0.001)(Table 6). The significant interaction indicates that there wasa decrease in percentage removal of phosphate in the Perlite
MSL system (P < 0.1) (Table 6). The percentage removal of phos-phate by the Leilehua MSL system (64–99%) (LSmean of 92.70)was greater than the Perlite MSL system (9–97%) (LSmean of59.41) (Fig. 3).Table 6 – A comparison of the effect of time and MSLsystem on phosphate removal as analyzed by SAS ProcMixed repeated measures analysis
Factor Probability of significance (P)
MSL systems 0.0292Time 0.0004MSL systems × time 0.0997
MSL systems as affected by sucrose addition and differentrates of aeration.
3.3. Second phase (year 2006)
3.3.1. The effect of aerationA comparison was made between no aeration and two differ-ent rates of aeration (28 L min−1 and 31 L min−1) in removalof inorganic N and phosphate during a sampling period of 19January to 27 April 2006 (Figs. 4 and 5).
The percentage removal of inorganic N was not signifi-cantly different between the MSL systems (P > 0.1) (Table 7).There was no significant difference in percentage removal ofinorganic N with aeration for both the MSL systems (P > 0.1)(Table 7). The non-significant interaction indicates that thetwo MSL systems behaved similarly in percentage removal of
Fig. 5 – Removal of phosphate in the Leilehua and PerliteMSL systems as affected by sucrose additions and differentrates of aeration.
e c o l o g i c a l e n g i n e e r i n g 3 2 ( 2 0 0 7 ) 1–10 7
Table 7 – A comparison of the effect of aeration and MSLsystem on inorganic N removal as analyzed by SAS ProcMixed repeated measures analysis
Factor Probability of significance (P)
MSL systems 0.8008Aeration 0.8214MSL systems × aeration 0.4330
Table 8 – A comparison of the effect of aeration and MSLsystem on phosphate removal as analyzed by SAS ProcMixed repeated measures analysis
Factor Probability of significance (P)
dLriratp((
3Asgt
ctg(tiL((
raws
Table 10 – A comparison of the effect of sucrose and MSLsystem on phosphate removal as analyzed by SAS ProcMixed repeated measures analysis
Factor Probability of significance (P)
MSL systems 0.0342Sucrose 0.1325MSL systems × sucrose 0.0980
Table 11 – A comparison of the effect of different rates ofaeration and MSL system on inorganic N removal asanalyzed by SAS Proc Mixed repeated measures analysis
Factor Probability of significance (P)
MSL systems 0.0088Aeration 0.0782MSL systems × aeration 0.0141
The percentage removal of phosphate was significantlyifferent between the MSL systems (P < 0.01) (Table 8). Theeilehua MSL system was more effective in percentageemoval of phosphate than the Perlite MSL system. Changesn aeration resulted in a significant difference in percentageemoval of phosphate (P < 0.1) (Table 8). The significant inter-ction indicates that the MSL systems behaved differently inhe removal of phosphate (P < 0.05) (Table 8). The removal ofhosphate by the Leilehua MSL system ranged from 42 to 91%
LSmean of 66.64) and was greater than the Perlite MSL system11–41%) (LSmean of 27.22) (Fig. 5).
.3.2. The combined effect of sucrose with aerationcomparison was made between the non-sucrose and
ucrose applications with constant aeration in removal of inor-anic N and phosphate from 16 February to 13 April and 25 Mayo 10 July 2006 (Figs. 4 and 5).
The MSL systems were not significantly different in per-entage removal of inorganic N (P > 0.1) (Table 9). However,here was a significant increase in percentage removal of inor-anic N with sucrose additions for both the MSL systemsP < 0.1) (Table 9). The non-significant interaction indicates thathe MSL systems behaved similarly in percentage removal ofnorganic N (P > 0.1) (Table 9). The inorganic N removal by theeilehua and the Perlite MSL system ranged from 9 to 89%LSmean of 48.77) and 10 to 92% (LSmean of 53.36), respectivelyFig. 4).
The MSL systems differed significantly in the percentage
emoval of phosphate (<0.05) (Table 10). There was no over-ll significant difference in percentage removal of phosphateith the sucrose application (P > 0.1) (Table 10). However, theignificant interaction indicates that the percentage removal
Table 9 – A comparison of the effect of sucrose and MSLsystem on inorganic N removal as analyzed by SAS ProcMixed repeated measures analysis
Factor Probability of significance (P)
MSL systems 0.6583Sucrose 0.0539MSL systems × sucrose 0.8913
MSL systems 0.8640Aeration 0.3546MSL systems × aeration 0.3249
of phosphate was increased in the Perlite system (P < 0.1)(Table 10). The removal of phosphate by the Leilehua MSL sys-tem ranged from 59 to 93% (LSmean of 76.31) and was moreeffective than the Perlite MSL system (11–75%) (LSmean of46.13) (Fig. 5).
3.3.3. The effect of different rates of aerationThree different rates of aeration (11 L min−1, 17 L min−1, and23 L min−1) were compared in removal of inorganic N andphosphate between a sampling period of 4 May to 10 July 2006when sucrose was added (Figs. 4 and 5).
The MSL system performance was not significantly differ-ent in the percentage removal of inorganic N (P > 0.1) (Table 11).There was no significant difference in percentage removal ofinorganic N with different rates of aeration between the MSLsystems (P > 0.1) (Table 11). The non-significant interactionindicates that the MSL systems behaved similarly in percent-age removal of inorganic N (P > 0.1) (Table 11). The removal ofinorganic N by the Leilehua and the Perlite systems rangedfrom 31 to 89% (LSmean of 60.33) and 43 to 92% (LSmean of62.24), respectively (Fig. 4).
There was a significant difference observed in percent-age removal of phosphate between the MSL systems (P < 0.1)(Table 12). There was no significant difference in removal ofphosphate with different rates of aeration (P > 0.1) (Table 12).The non-significant interaction indicates that the MSL sys-tems behaved similarly in removal of phosphate (P > 0.1)(Table 12). The percentage removal of phosphate by the Leile-
hua MSL system ranged from 59 to 93% (LSmean of 73.71) wasgreater than the Perlite MSL system (17–75%) (LSmean of 46.77)(Fig. 5).Table 12 – A comparison of the effect of different rates ofaeration and MSL system on phosphate removal asanalyzed by SAS Proc Mixed repeated measures analysis
Factor Probability of significance (P)
MSL systems 0.0937Aeration 0.1373MSL systems × aeration 0.2538
8 e c o l o g i c a l e n g i n e e r i n
Fig. 6 – The relationship between P sorbed and soil solutionP in Leilehua and Honouliuli soil.
4. Discussion
4.1. Performance of the MSL system in removinginorganic N
The efficiency of the MSL systems in removing inorganic Nfrom dairy effluent was not significantly different through-out the study (years 2005 and 2006). Both MSL systems usedfor the aerobic layers, whether Leilehua or Perlite, were sim-ilarly effective in removing inorganic N. However, the MSLsystems were significantly different in removal of inorganicN over time in 2005. The removal rate of inorganic N in efflu-ent decreased over time. We hypothesized the decrease mightbe due to inadequate aeration in the aerobic layer or decreasedmicroorganism-available carbon in the anaerobic layer andtested this by adding supplemental aeration and sucrose (asa carbon source) in 2006. The systems were not significantlydifferent in removal of inorganic N with supplemental aera-tion. However, the removal of inorganic N was significantlyincreased in both the MSL systems with the application ofsucrose. The increased removal rate was likely due to theadditional carbon provided by sucrose applications, whichenhanced microbial activity and thus increased the denitri-fication in both MSL systems. The removal of inorganic N wasnot significantly different with different rates of aeration in2006. There were some pauses in effluent delivery by the MSLsystems in 2005 and sudden drops in removal of inorganic Nseemed to related to these pauses.
4.2. Performance of the MSL system in removingphosphate
The efficiency of the MSL systems in removing phosphate fromdairy effluent varied significantly during the study (years 2005and 2006). The Leilehua MSL system was consistently moreeffective in removing phosphate than the Perlite MSL system.This was probably because of the high P sorption capacity ofthe Leilehua soil in the Leilehua MSL system (1600 �g P g−1 soil)
(Fig. 6) which adsorbs phosphate from the effluent. Theremoval of phosphate was significantly decreased over timeby the Perlite MSL system in 2005. We hypothesized that thedecrease in removal of phosphate by the Perlite system mightg 3 2 ( 2 0 0 7 ) 1–10
be a result of decreased microorganism-available carbon inthe anaerobic layer related to reduced iron movement into theaerobic layer. Supplemental aeration and carbon (as sucrose)were applied in 2006 to increase the efficiency of the MSLsystems in removing phosphate. The percentage removal ofphosphate was significantly increased with the application ofsucrose in the Perlite MSL system. This might be because theadditional sucrose carbon increased the activity of microor-ganisms resulting in more oxygen consumption and enhancedreducing conditions in the anaerobic layer chemically reduc-ing and moving iron into the aerobic layer where it couldprecipitate as ferric iron and sorb the phosphate in effluent.The hypothesized decrease in microorganism-available car-bon in 2005 seems to be supported by the sharp increasein percentage removal of phosphate by the Perlite MSL sys-tem with sucrose applications observed in 2006. The removalof phosphate was significantly increased with supplementalaeration by the Leilehua MSL system. This might be becauseof the sufficient aeration in the Leilehua MSL system oxi-dized ferrous iron to ferric iron in the aerobic layer, leadingto higher adsorption of phosphate by the soil colloids. Thesucrose application did not increase the already high removalof phosphate in the Leilehua MSL system. The removal ofphosphate was not significantly different with different ratesof aeration when comparing the two MSL systems in 2006.The systems consistently removed phosphate with differentrates of aeration. Thus, from the results of supplemental aer-ation and sucrose applications it appears that the phosphateremoval mechanism is likely different between the two MSLsystems. The removal of phosphate in the Leilehua MSL sys-tem was mainly due to sorption by iron in the aerobic layer,whereas in the Perlite MSL system it appears to be due to threesteps, solubilization in the anaerobic layer, movement into theaerobic layer, and precipitation as ferric oxide.
4.3. Use of MSL-treated effluent
The Hawaii State Department of Health has three differentcategories of recycled water—R-1, R-2, and R-3 water—whichare listed in Table 13 with specific criteria (Hawaii StateDepartment of Health, 2002). R-1 is the highest quality recy-cled water. It has been filtered and disinfected. It can be usedin any form of irrigation served by fixed irrigation systems sup-plied by buried piping for turf and landscape irrigation of golfcourses, parks, elementary schools, roadsides, and residentialproperty where managed by an irrigation supervisor (HawaiiState Department of Health, 2002). R-2 is a slightly lowerquality recycled water. It is secondary (biologically) treatedwastewater that has also been filtered and disinfected (HawaiiState Department of Health, 2002). Its use requires more cau-tion and restrictive controls than R-1 water. R-3 is the leastpure class of recycled water. R-3 quality water is wastewaterthat has been treated to the secondary level. It can only beused for irrigation at places where people rarely go (HawaiiState Department of Health, 2002).
The average concentration of NO −-N and phosphate, and
3fecal coliform colonies in MSL-treated effluent of our studyis given in Table 14. If we compare our study with the recy-cled water requirements of State Department of Health inHawaii, the MSL-treated effluent comes in as R-3 water. MSL-
e c o l o g i c a l e n g i n e e r i n g 3 2 ( 2 0 0 7 ) 1–10 9
Table 13 – Recycled Water Standards (Hawaii State Department of Health, 2002)
Type of recycled water Treatment Recycled water quality Recycled water monitoring
R-1 Oxidizeda ≤23 fecal coliform/100 mL Coliform: no more than one sample in any 30-day periodFilteredb Nitrate ≤ 10 mg L−1
Disinfectedc Total phosphorus ≤ 1.0 mg L−1
R-2 Oxidized ≤200 fecal coliform/100 mL Coliform: no more than one sample in any 30-day periodFiltered Nitrate ≤ 10 mg L−1
Disinfected Total phosphorus ≤ 1.0 mg L−1
R-3 OxidizedSecondaryUndisinfected
a Wastewater in which the organic matter has been stabilized.b The passing of wastewater through natural undisturbed soils or filter media such as sand.c The destruction, inactivation, or removal of pathogenic microorganisms by chemical, physical, or biological means. Disinfection may be
accomplished by chlorination, ozonisation, other chemical disinfectants, UV radiation, membrane processes, or other processes.
Table 14 – Concentrations of MSL-treated effluent
NO3−-N (�g mL−1) Phosphate (�g mL−1) Fecal coliform (cfu/100 mL)
May–October 2005a
Leilehua MSL system 2.15 ± 3.25 0.46 ± 0.56 658 ± 1321Perlite MSL system 3.81 ± 5.35 2.16 ± 1.72 459 ± 674
May–July 2006b
Leilehua MSL system 2.48 ± 2.68 2.83 ± 1.38 64 ± 95Perlite MSL system 5.04 ± 9.24 5.25 ± 2.74 36 ± 53
a First phase of data without aeration and sucrose addition (mean ± S.D., n = 21).t rate
t(1ttt
5
RpoTipadrscpmtcecou
r
b Second phase of data with different rates of aeration and constan(mean ± S.D., n = 9).
reated effluent meets the criteria of nitrate and fecal coliformMay–July 2006) of R-2 water and approaches the criteria for R-
water. Improvements in efficiency of the type examined inhis study are needed to meet the phosphate criteria. In addi-ion a process, such as chlorination is needed to disinfect thereated effluent.
. Conclusions
esults of this study showed that both MSL systems have theotential to remediate dairy effluent. The percentage removalf inorganic N was high and similar in both the MSL systems.he percentage removal of phosphate was high to very high
n the Leilehua MSL system and it removed considerably morehosphate than the Perlite MSL system. The supplementaleration, which was applied in the second phase of the study,id not significantly improve the removal of inorganic N. Theemoval of phosphate, however, increased in the Leilehua MSLystem with additional aeration. Application of sucrose withonstant aeration was crucial for removing inorganic N andhosphate. It appears that sucrose additions increased theicrobial activity in the MSL systems which helped to increase
he removal of inorganic N and phosphate. The sucrose appli-ations have the potential to improve MSL systems treatment
fficiency. The installation of MSL systems is simple and basi-ally requires only electricity, freshwater, a constant supplyf effluent and a very small amount of land. The materialssed in the system are inexpensive and easily obtainable.of sucrose, considered as the optimal management of the system
The MSL-treated effluent approaches R-1 water criteria, withimprovements in P removal still needed.
Acknowledgement
We gratefully acknowledge the USDA T-STAR Program, Univer-sity of Hawaii for the support of this research.
e f e r e n c e s
Attanandana, T., Saitthiti, B., Thongpae, S., Kritapirom, S.,Luanmanee, S., Wakatsuki, T., 2000. Multi-media-layeringsystem for food service wastewater treatment. Ecol. Eng. 15,133–138.
Caro-Costas, R., Abruna, F., Figarella, J., 1972. Effect of nitrogenrates, harvest interval and cutting heights on yield andcomposition of stargrass in Puerto Rico. J. Agric. Univ. PuertoRico 56, 267–279.
Fukumoto, G.K., Duponte, M.W., Lee, C.N., 2000. LivestockIndustry Partnering for Education and ProgramImplementation: Nutrient Management Alternatives andPollution Prevention Planning. Phase I. A report submitted tothe State of Hawaii, Governor’s Agriculture CoordinatingCommittee (GACC).
Guo, F., Yost, R.S., 1998. Partitioning soil phosphorus into threediscrete pools of differing availability. Soil Sci. 163 (10),822–833.
Hawaii State Department of Health Wastewater Branch, 2002.The Health State Guidelines for the Treatment and Use of
e e r i n
10 e c o l o g i c a l e n g i nRecycled Water. Available on-line at http://hawaii.gov/health/environmental/compliance/sb library/livestock.pdf (VerifiedJanuary 5, 2006).
Hobo Weather Station, 2001–2003. Onset Computer Coporation.Procasset, MA.
Hawaii State Department of Health Wastewater Branch, 1996.The Health State Guidelines for Livestock WasteManagement. Available on-line at www.state.hi.us/health/environmental/water/wastewater/pdf/reuse-final.pdf (VerifiedMay 5, 2006).
Ikenberry, C.D., Mankin, K.R., 2000. Review of Vegetative FilterStrip Performance for Animal Waste Treatment. Presented atthe 2000 ASAE Mid-Central Meeting, Paper No. MC00128.American Society of Agricultural Engineers. St. Joseph,MI.
Kuo, S., 1996. Phosphorus. In: Sparks, D.L. (Ed.), Methods of SoilAnalysis, Part 3. Chemical Methods—SSSA Book Series No. 5.SSSA, Madison, WI, pp. 908–909.
Littell, R.C., Milliken, G.A., Stroup, W.W., Wolfinger, R.D., 1996.SAS System for Mixed Models. SAS Institute, Cary, NC.
Littell, R.C., Henry, P.R., Ammerman, C.B., 1998. Statisticalanalysis of repeated measures data using SAS procedures. J.Anim. Sci. 76, 1216–1231.
Luanmanee, S., Attanandana, T., Masunaga, T., Wakatsuki, T.,2001. The efficiency of a multi-soil-layering system ondomestic wastewater treatment during the ninth and tenthyears of operation. Ecol. Eng. 18, 185–199.
Luanmanee, S., Boonsook, P., Attanandana, T., Saitthiti, B.,Panichajakul, C., Wakatsuki, T., 2002. Effect of intermittentaeration regulation of a multi-soil-layering system ondomestic wastewater treatment in Thailand. Ecol. Eng. 18,415–428.
Manariotis, I.D., Grigoropoulos, S.G., 2003. J. Environ. Sci. Health
A; Toxic Hazard. Subst. Environ. Eng. 38, 2057–2068.Mulvaney, R.L., 1996a. Nitrogen-Inorganic Forms, Ammonium. In:Sparks, D.L. (Ed.), Methods of Soil Analysis, Part 3, ChemicalMethods—SSSA Book Series No. 5. SSSA, Madison, WI, pp.1153–1155.
g 3 2 ( 2 0 0 7 ) 1–10
Mulvaney, R.L., 1996b. Nitrogen-Inorganic Forms, Nitrate. In:Sparks, D.L. (Ed.), Methods of Soil Analysis, Part 3, ChemicalMethods—SSSA Book Series No. 5. SSSA, Madison, WI, pp.1155–1159.
Prochaska, C.A., Zouboulis, A.I., 2003. Performance ofintermittently operated sand filters: a comparable study,treating wastewaters of different origins. Water Air Soil Pollut.147, 367–388.
SAS Institute, 2004. The SAS system for Windows. Release 9.1.SAS Institute, Cary, NC.
Schaafsma, J.A., Baldwin, A.H., Streb, C.A., 2000. An evaluation ofa constructed wetland to treat wastewater from a dairy farmin Maryland, USA. Ecol. Eng. 14, 199–206.
Sigma Plot, 2004. Systat Software. Version 9.0. Systat Inc.,Richmond, CA, USA.
Smith, V.H., Tilman, G.D., Nekola, J.C., 1999. Eutrophication:impacts of excess nutrient inputs on freshwater, marine, andterrestrial ecosystems. Environ. Pollut. 100, 179–196.
Soil Survey Staff, 2006. National Soil Survey CharacterizationData. Soil Survey Laboratory, National Soil Survey Center,USDA-NRCS-Lincoln, NE. Available on-line at http://ssldata.nrcs.usda.gov/querypage.asp (Verified 5 April 2005).
U.S. Department of Agriculture-Soil Conservation Service(USDA-SCS), 1992. Agricultural Waste Management FieldHandbook. Washington, DC.
Valencia-Gica, R.B., Wilcox, V., Yost, R.S., Evensen, C.I., 2004.Nutrient uptake and effluent clean-up potential of tropicalpasture grasses—Preliminary Report. University of Hawaii atManoa (unpublished).
Wakatsuki, T., Esumi, H., Omura, S., 1993. High performance andN & P removable on-site domestic waste water treatmentsystem by multi-soil-layering method. Water Sci. Technol. 27,31–40.
Wright, P.E., 1996. Prevention, collection and treatment ofconcentrated pollution sources on farms. In: AnimalAgriculture and the Environment: Nutrients, Pathogens andCommunity Relations. Northeast Regional AgriculturalExtension Service, Ithaca, NY, pp. 142–158.
