Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.enzyme.chem.msu.ru/ekbio/article/2002_39.pdf Дата изменения: Mon Dec 30 14:36:06 2002 Дата индексирования: Mon Oct 1 22:06:41 2012 Кодировка:

Combinedbiological and physico-chemicaltreatment of
filtered pig manure wastewater: pilot investigations
s. Kalyuzhnyi*, v. Sklyar', A. Epov'l. Arkhipchenko", I. Barboulina", o. Orlova" and A. Klapwijk'" Dept.of Chemical Enzymology, Chemistry Faculty, Moscow State University, 119899 Moscow, Russia

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Netherlands Abstract

Agricultural Microbiology, Podbelsky shosse 3, 189620 St-Petersburg-Pushkin 8, Russia of Environmental Technology, Wageningen University, 6700 EV Wageningen, The

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Combined

biological

and physico-chemical

treatment

of filtered pig manure wastewater

has been

investigated the pilot installation on operatedunderambienttemperatures (15-20.C) and included:i) UASBreactor for elimination of major part of COD from the filtrate; (ii) stripper of CO2 + tluidised bed crystallisator

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for phosphate(andpartiallyammonia) removal from the anaerobic effluentsin the form of insolubleminerals struvite (MgNH4PO 4) and hydroxyapatite (Ca5(PO 4)aOH); (iii) aerobic-anoxic biofilter for polishing the final effluent (elimination of remaining BOD and nutrients). Under overall hydraulic retention time (HRT) for the system of 7.8 days, the total COD, inorganic nitrogen and total phosphorous removals were 88, 65 and 74%, respectively. A decrease of the overall HRTto 4.25 days led to 91,37 and 82% removals for total COD, inorganic nitrogen and total phosphorus removals, respectively. The approaches for further improvement of effluent quality are discussed. Keywords Integrated system; nutrient removal; phosphate precipitation; pig manure wastewater; UASB
reactor

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Introduction

More than 30 million tonnes of pig manure wastewater containing 2-4% total solids is produced in Russia at big complexes and medium-scale farms due to flushing technology usedfor cleaning (Arkhipchenko, 2000). A possible solution for sustainableutilisation and treatment of diluted manure streams is the preliminary mechanical separation of solid and liquid fractions followed by separatebiological and physico-chemical treatment of both fractions (Kalyuzhnyi et al., 1999). Various treatment stepsinvolved in this approach were investigated on the laboratory level (Kalyuzhnyi et al., 1999, 2000) during the execution of the joint Russian-Dutch project "The development of integrated anaerobicaerobic treatment of liquid manure streamswith maximisation of production of valuable by-products (fertilisers, biogas) and re-utilisation of water" (1999-2001). They servedas a basis to design a pilot installation (Figure 1) for treatment of filtered pig manure wastewater. This paper discussesthe results obtained during the experimental evaluation of this installation: i) COD elimination from filtered pig manure wastewaterusing a UASB reactor; ii) optimisation of phosphateprecipitation from anaerobic effluents; iii) performance of a biofilter for the removal of remaining BOD and nutrients. Materials and methods
Manure wastewater and pilot installation

The raw manure wastewater (RMW) was taken directly from a pig farm, using a flushing technology for cleaning and located on the territory of municipal solid waste treatment plant in St. Petersburg.The RMW was decantedand filtered through a tissue filter (in full

79


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VASEreactor.TheUASBreactorwasmade from transparent plasticsandhadthefollowing size:cross-section (rectangular) 22.6cm2,height- 206cm,workingvolume- 44.61. It wasseeded with 101of anaerobic sludge originatingfrom ananaerobic digester treating
sewagesludge (Moscow). During the start-up period (1 month), the reactor was operatedin semi-continuous mode to adapt the sludge to new feeding substrate.Then it was switched by decreasinghydraulic retention time (HRT).

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on a continuous regimeanda gradualincrease organicloadingrate(OLR) wasapplied of

Phosphate precipitation block. This block consisted of air stripper (diameter - 20 cm, height - 20 cm, working volume - 6 1) for CO2 removal to increasepH and fluidised bed crystallisator (FBC, diameter- 7.8 cm, height 105 cm, total volume-51) forcrystal1isation of phosphateminerals such as struvite (MgNH4PO4) and hydroxyapatite (Ca5(PO4)30H). Both reactors were made from transparentplastics. The FBC was initially filled by 1 kg of washedsand(0.25-0.5 rom fraction) as a sourceof nuclei to promote phosphatecrystallisation from supersaturated effluents of the stripper. The fluidisation was performed using an airlift loop. Biofilter. The biofilter was madefrom transparentplastics and packed by road metal (0.5-2 cm fraction). It had the following size: diameter - 13 cm, height - 145cm, working volume - 19 1)and functioned in alternating aerobic/anoxic regime for treatment of the FBC effluent. During aerobic phase(duration - 30 or 20 min), the feeding was stopped,while air at a
Table 1 Range of variation of some characteristics of FMW, gll (average values are given in brackets) CODIot CODss COD,., COD,., pH N.H3 Plot PPQ4

3.7-12.4 (8.1)

0.2-4.9 (2.1)

0.3-3.8 (1.2)

2.6-9.9 (4.9)

5.2-8.7 (6.8)

0.37-1.45 0.08-0.24 (0.75) (0.15)

0.04-0.14 (0.09)

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time cycle of 1 hour) controlledall 3 pumpsused.Secondary (nitrifying) sludgefrom wastewater treatment plantof pig complex "Vostochnyi"(Leningrad province) used was as seedsludgefor formationof the attached biofilm. The excess sludgewasperiodically of
withdrawn from the top ofbiofilter.

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Analyses. COD wasanalysed spectrophotometric usingHachtubes.Raw samples ally of influentsor effluentswereusedfor determination total COD (CODtoJ, ~m folded of 4.4
paper-filtered (Schleicher & Schue1l5951/2' Germany) samplesfor determination offiltrated COD (CODfilJ and 0.45 ~m membrane-filtered (Schleicher & Schuell ME 25, Germany) samplesfor determination of soluble COD (CODsoJ.The suspended solids COD (CODss) and colloidal COD (CODcoJ were calculated by the differences between CODtot and CODfiltr' CODfilt and CODsol' respectively. All other analyses were performed 2-3 times per week by standardmethods(APHA, 1992) or asdescribedpreviously (Kalyuzhnyi et al., 1999, 2000). Due to technical problems, the measurements total nitrogen were not of made. All gas measurements are recalculated to standard conditions (1 atm, DOC). Statistical analysis of data was performed using Microsoft Excel. Results and discussion
COD elimination using UASB reactor

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The results of the UASB treatment of the FMW are presentedin Figure 3 and they are outlined in Table 2. It can be seenthat during Period I (days 0-32, Figure 2a), the HRT was on the average 3.5 days resulting in the averageOLR of 1.7 g COD/l/d (Table 2). The total COD removal was 45% while removals of suspendedsolids (SS), colloidal and soluble COD fractions were 69, 59 and 38% (on the average),respectively (Table 2). In spite of big fluctuation of influent pH, the effluent pH was rather stable - around 7.5 (Figure 2c). The specific methane production was also a subject of some variations and accounted (on the average)for 0.23 nl/l/d. This value is somehowbelow the theoretically expectedone (0.27 nl/l/d) taking into account the observed COD removal. The discrepancy can be mainly attributed to entrapment of some part of the undigested SS by the reactor sludge bed. As expected, the ammonia concentrations slightly increased due to anaerobic hydrolysis of proteinaceoussubstances the FMW (Figure 2d). On the contrary, the concentrationsof in total phosphorus and phosphate substantially dropped during the anaerobic treatment of FMW (Figures 2e-f and Table 2). As in laboratory experiments (Kalyuzhnyi et al., 2000), this was attributed to partial precipitation of phosphate minerals (presumably: hydroxyapatite and struvite) inside ofUASB reactor. After a decreaseofHRT during Period II (days 33-75, Figure 2a) to on the average 2 days resulting in an increase of OLR to 5 g COD/l/d (on the average, Table 2), the total COD removal step-wise increasedto around 70% (Figure 3b, 50-75). This was due to
increased removal of colloidal and soluble COD fractions (on the average

-

74 and 63%,

respectively) compared to Period I (Table 2). On the contrary, a slight decreaseof SS removal was detecteddue to increasedwash-out of sludge and other entrappedparticulate matter clearly observedthroughout Period II. The specific methaneproduction rate (Figure 2c, days 33-75) followed a tendency of increasing total COD removal (Figure 2b, days 33-75) though some discrepancieswith the theoretically expected one were observed. In spite of acidic influents fed to the reactor, especially in the end of Period II (Figure 2c), the effluent pH was stabilised around 7 due to volatile fatty acids (VFA) consumption (data

81


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HRT, days OLR,gCOD/l/d

3.2-4.3 (3.5) 3.7-10.1(6.0)
2.2-4.4 (2.9)
% 21-56 (45)

1.4-3.0 (2.0) 6.1-12.4(9.3)
2.7-6.6 (3.7)
20-77 (60)

InfluentCODlol,g/l
COD removal,

1.3-2.9(1.7)

3.0-7.4(5.0)

Effluent CODlo" g/l
Total

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Influent CODss' g/l

0.2-1.9 (1.2)

0.1-4.9 (2.2)

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EffluentCODss,g/l Suspended solidsCOD removal,% InfluentCOD I' g/l co
Effluent CODcol' g/l Colloidal COD removal, % Influent CODsol' g/l EffluentCODsol,g/l Soluble COD removal, % Influent pH Effluent pH CH4 production, nlll reactorld Influent N-NH3, g/l Effluent N-NH3, g/l Influent total phosphorus, g/l Effluent total phosphorus, g/l Total phosphorus removal, % Influent P-PO4' g/l

0.1-1.1(0.5) 55-96 (69) 0.3-2.3 (0.9)
0.1-0.6 (0.3) 33-96 (59) 2.6-4.5 (3.4) 1.1-3.1 (2.1) 20-57 (38) 6.7-8.7(7.7) 7.2-7.9 (7.5)

0.4-2.7(1.1) 17-94 (56) 0.5-2.3 (1.3)
0.1-1.3 (0.5)

59-91 (74)
3.0-10.0 (5.8) 0.9-3.2(2.1) 38-84 (63)

5.2-6.9(6.1)
6.7-7.7 (7.1)

0.14-0.34 (0.23) 0.37-1.45 (0.78) 0.55-1.26 (0.90)
0.08-0.19 (0.15)

0.34-1.41 (0.8) 0.52-1.1 (0.74) 0.56-1.45 (0.84)
0.12-0.24 (0.15)

0.07-0.14 (0.11) 16-47 (29)
0.04-0.08 (0.07) 0.03-0.07 (0.05)

0.09-0.13 (0.11)
8-53 (27) 0.06-0.14 (0.10) 0.04-0.08 (0.05)

EffluentP-PO4, g/l P-PO4removal, %

5-67(31)

32-81(50)

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Figure 2 Performance of UASB reactor treating the FMW: a - HRT and OLR; b - total influent and effluent COD and total COD removal; c - influent and effluent pH and methane production per litre of reactor volume per day; d - influent and effluent ammonia; e - total influent and effluent phosphorus and total phosphorus 82 removal; f

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influent and effluent phosphate and phosphate removal


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undersub-mesophilic temperatures (15-20°C)werecomparable the resultsobtained to in the lab scaletrials undermesophilic regime(30°C)(Kalyuzhnyiet al., 2000).However, suchexhaustion easilydegradable of COD(e.g.VFA) in theanaerobic effluentsmightcreateproblems biologicalpost-treatment for biologicalN andP removal). for (e.g.
Phosphate removal from anaerobic effluents via precipitation

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In spite of substantial precipitation of phosphate minerals inside of UASB reactor, this

process incomplete canbecontinued adjusting pH to theoptimalsupersatuwas and by the
rating value, which is above 9 (Kalyuzhnyi et al., 2000). The results of continuous pilotscale phosphate precipitation promoted by air stripping of CO2 to increase pH and crystallisation in the FBC are shown in Figure 3 and Table 3. The total HRT in the phosphate precipitation block was initially set as 1 day (-0.6 days in the stripper and - 0.4 days

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in the FBC). During days 0-32 (Figure 3a), this block demonstratedvery good efficiency with regard to phosphateremoval- 84% (on the average, Table 3) ensuring the effluent phosphateconcentration below 10 mg/!. Some drop in ammonia concentrations was also detected (Figure 3b, days 0-32). Besides suspected struvite formation, some losses of ammonia probably occurred due to its stripping into the gasphaseat pH values higher than 8 which were usually observedin the precipitation block. In addition, biological nitrification of ammonia was gradually developed in the FBC as the effluents contained 0.2-0.3 g N-NO3 during days 35-45 (data not shown). Since occurrence of ammonia nitrification, which becamealmost complete during days 38-45 (Figure 3b) and led to pH drop below 8, had a deteriorating impact on the phosphateremoval (Figure 3a, days 38-45), the total HRT for precipitation block was reduced to - 0.25 days at day 47. This resulted in a gradual increaseof phosphateremoval (Figure 3a, days 47-75) to the averagevalue of73% with the averageeffluent phosphateconcentration of 15 mg/l for Period 11-2(Table 3). Also ammonia nitrification almost stopped as only negligible concentrations of nitrate and nitrite were observedin the effluent during this period (data not shown). The overall removal of ammonia (presumably due to struvite precipitation and stripping) was accountedfor 32% (Table 3).
Biofilter performance

A successful start-up of biofilter in the nitrifying mode was achieved in 1 month. Then it was switched on alternating (aerobic-anoxic) operation and the corresponding results are presentedin Figure 4 and Table 4. During Period I (days 0-32), when duration of anoxic and aerobic phaseswas 30 min each,the averageHRT was 3.3 days while the averageOLR was 0.86 g COD/l/d (Table 4). The averagetotal COD removal accountedfor 74%, though the removal of individual COD fractions was not uniform- 84, 40, 79% (on the average)for
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83


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HK I , cays Influent P-PO4' gll Effluent P-PO4, gll P-PO4 removal, %

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0.027-0.071 (0.050) 0.001-0.010 (0.007) 64-98 (84) 0.548-1.260 (0.896) 0.343-0.845 (0.560) 13-53 (37)

0.046-0.081 (0.057) 0.011-0.027 (0.015) 56-83 (73) 0.670-1.450 (0.916) 0.530-0.980 (0.747) 23-46 (32)

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SS,colloidalandsoluble matter, respectively (Table4). In spiteof significantvariations in influent concentrations, total COD effluentconcentrations the werefairly stable, slightly
oscillating around 0.72 g COD/l (Figure 4b). The efficiencies of nitrification and denitrification (Figures 4d and e) were 75 and 65% (on the average)resulting in the averageinorganic nitrogen removal of 49% (Table 4). A more than double increase of phosphate concentrationsin the biofilter effluents comparedto thoseof phosphateprecipitation block (see Tables 3 and 4) was likely due to the dissolution of the small phosphateprecipitates entering into the biofilter with the influents (these small precipitates were not accounted during soluble phosphateanalysis becausethe sampleswere centrifuged before analysis). Due to occurrenceof ammonia nitrification in the phosphateprecipitation block resulting in the low influent ammonia concentrations entering to the biofilter (Figure 4d, days 33-46), the duration of anoxic phaseof biofilter operation was increasedto 40 min and that of aerobic phasewas decreasedto 20 min keeping the averageHRT on the samelevel of

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Time, days Time, days Figure 4 Operational performance of biofilter treating effluents from nutrient precipitation block: a - HRT and OLR; b - total influent and effluent COD and total COD removal; c
nia loading rate (ALR); d - influent and effluent ammonia 84 removal and inorganic nitrogen removal; f and ammonia

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Aerobicphase,min : Anoxicphase,min ' HRT,days
OLR, 9 COD/l/d $ALR, 9 N-NH4/1/d Influent CODtot' g/l Effluent CODtot' 9/1 Total COD removal, %

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1.06-1.61 (1.39) 0.268-0.427 (0.365) 2.60-4.50 (3. 15) 0.65-0.94 (0.82) 64-79(71) 0.10-2.15(0.54)

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0.28-1.56 (0.86) 0.05-0.299 (0.168) 2.20-4.42 (2.93) 0.55-0.99 (0.72) 60-85(74) 0.19-1.17(0.52)

0.69-1.20 (1.04) 0.006-0.066 (0.028) 2.90-3.84 (3.55) 0.38-0.50 (0.45) 61-90(85) 0.40-3.17(1.74)

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EffluentCODss,g/l CODss removal,% InfluentCODco!'9/1 EffluentCODcol'9/1 CODcol removal,% InfluentCODooi' g/l EffluentCODsoi'g/l CODool removal,% InfluentpH EffluentpH InfluentN-NH3'g/l EffluentN-NH3'g/l N-NH3removal,% EffluentN-NO3,g/l 'N-NO3 removal,% #Inorganic nitrogenremoval,% Effluent total P, 9/1 EffluentP-PO4,g/l

InfluentCODss,g/l

0.01-0.06(0.05) 50-95 (84) 0.10-0.60 (0.31) 0.08-0.50 (0.23) 6-73 (40) 1.14-3.13(2.10) 0.08-0.62 (0.43) 69-93 (79) 7.6-9.0 (8.5) 7.0-8.7(8.2) 0.343-0.845 (0.560) 0.055-0.230 (0.134) 67-87 (75) 0.025-0.268 (0.140) 25-89 (65) 22-70 (49) 0.020-0.044 (0.031) 0.016-0.020 (0.018)

0.00-0.03(0.02) 98-100 (99) 0.14-1.31 (0.45) 0.01-0.07 (0.04) 75-97 (86) 2.14-2.80(2.36) 0.35-0.43 (0.39) 81-88 (83) 7.2-8.7 (7.8) 7.8-8.5(8.2) 0.060-0.210 (0.094) 0.004-0.045 (0.014) 64-94 (84) 0.046-0.325 (0.195) 14-87 (45) 14-78 (42) 0.022-0.049 (0.031) 0.016-0.022 (0.020)

0.03-0.24(0.12) 65-90 (79) 0.08-1.30 (0.70) 0.05-0.26 (0.15) 43-86 (63) 0.93-3.23(1.89) 0.42-0.67 (0.56) 44-81 (68) 7.6-8.1 (7.9) 7.7-8.1(7.9) 0.503-0.835 (0.738) 0.280-0.563 (0.448) 21-49 (39) 0.003-0.075 (0.017) 77-99 (94) 20-49 (37) 0.011-0.034 (0.021) 0.010-0.024 (0.018)

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$ALR- ammonia loadingrate 'Calculatedas: (1-[N-NO3Je/([N-NO~in [N-NH3Jin [N-NH3JeJ}'100 + #Calculated {1-([N-NO3Jef [N-NH~eJ/([N-NO3Jin[N-NH~in)}'100 as: + +

3.3 days during Period 11-1 (days 33-46, Table 4). In spite of increase of the average OLR till 1.04 g CODIl/d, the total COD removal as well as COD removals of individual COD fractions also increased (compared to Period I) resulting in the average effluent concentration of total and soluble COD of 0.45 and 0.39 g/l (Table 4). It is likely that the latter concentration represents a hardly biodegradable (neither under anaerobic nor under aerobic/anoxic conditions) fraction of COD in the pig manure wastewater. Though the effluent ammonia concentrations were relatively low - around 0.014 g Nil (Figure 4d, days 33-46), the inorganic nitrogen removal was on the average 42% (Table 4) due to insufficient development of denitrification process resulting in high effluent nitrate concentra-

tions - 0.195 g Nil (on the average). It is likely that the concentration of easily biodegradable COD was insufficient to fulfil the denitrification requirements of the system.
In order to improve the nitrate removal, the HR T was decreased to around 2 days (Figure 4a, Table 4, Period 11-2) while duration of anoxic and aerobic phases was equalised to 30

min each. As a result, the average OLR increased to 1.39 g CODNd but the total COD
removal as well as COD removals of individual COD fractions decreased with respect to of Period 11-1, being comparable with those for Period 1 (Table 4). The better availability

easily biodegradable COD immediately resulted in an almost complete nitrate removal
(Figure 4, days 47-87) and the average effluent nitrate concentration accounted forO.017 g Nil during this Period. However, this operation regime had a detrimental effect on nitrifica-

tion - the average ammonia concentration accounted for 0.448 g Nil. Besides higher

85


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-Period I; b- Period 11-2 (FMW -filtered manure wastewater, UASB- UASB reactor; PPB-phosphate precipitation block; BF - biofilter)

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ammonia loadingrateapplied(lessammonia strippingin thePPB),this wasprobablydue
to decreaseof concentration of autotrophic nitrifying bacteria in the biofilter being outcompeted by heterotrophic microflora under the elevated OLR imposed on the system

duringPeriod11-2.
Figure 5 summarisesthe averagedata obtained in the pilot trials of combined biological and physico-chemical treatment of FMW (Figure 1) during Periods I and 11-2(the data for period II-I are not shown due to occurrence of nitrification in the PBB, which should be avoided by decreasing HRT in this block). It is seen that under the overall HRT for the systemof7.8 days (3.5 days in the UASB + 1 day in the PPB + 3.3 days in the biofilter), the total COD, inorganic nitrogen and total phosphorus removals were 88, 65 and 74%, respectively (Figure 5a). A decreaseof the overall HRT to 4.25 days (2 days in both the UASB and biofilter and 0.25 days in the PPB) led to 91, 37 and 82% removals for total COD, inorganic nitrogen and total phosphorusremovals, respectively (Figure 5b). Conclusions 1. The UASB reactor was quite efficient for removal of bulk COD presentedin the FMW even during operation under sub-mesophilic conditions (15-20°C). 2. The PPB was able to decreasethe concentration of soluble phosphatein the anaerobic effluents up to 7-15 mg P/l, but the measureshould be taken to prevent an entranceof small phosphateprecipitates into the biofilter where they can dissolve giving a rise in soluble phosphateconcentrations of the final effluents. The formed in the PPB phosphate minerals (presumably, struvite and hydroxyapatite) have a perspectiveto be sold as fertilisers or as raw material for this industry (e.g. the price of magnesium-ammonia phosphate in Russia is 100-150$/ton). However, stripping of ammonia in the FBB should be minimised, since ammonia releaseto the atmospherecausesacid rains. The latter can also be prevented by installation of acid tramp (e.g. with concentratednitric acid) before dischargeof stripped air into the environment. The concentratedammonia nitrate formed in the tramp can be used as raw material for fertiliser/chemical industry or directly as a liquid nitrogen fertiliser. 3. The application of aerobic/anoxic biofilter asa sole polishing step was acceptablefrom aestheticpoint of view (the effluents were transparentand almost colourless and odourless) and BOD elimination (the resting COD was hardly biodegradable).But the effluent nutrient concentrations(especially nitrogen) were far from the current standards for direct discharge of treated wastewater. The possible actions to improve an overall nitrogen removal in this system can include further playing with HRT and increaseof duration of aerobic phaseto achieve at least a complete nitrification. We are currently investigating thesepossibilities. 4. If the nitrogen removal will be further optimised, the possibility of re-use of treated
86

wastewater flushing shouldbe investigated for with regardto pathogen limits and


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Acknowlegements ThefinancialsupportofNWO(grantNo 047-07-18) gratefullyacknowledged. is References
APHA (1992).Standard Methods Waterand Wastewater for Examination,17thed.Amer. Public Health Assoc.,Washington, DC. Arkhipchenko,I.A. (2000).The livestockwastein Russia:currentsituation.In: Proc.Internat. Con!
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Microbial ecotechnology in processing of organic and agricultural wastes" (22-23 August, 2000, St.

Petersburg, Russia), Archipchenko I.A. and Kalyuzhnyi S.Y. (eds.), pp. 49-53. Kalyuzhnyi, S., Sklyar, Y., Fedorovich, Y., Kovalev, A., Nozhevnikova, A. and Klapwijk, A. (1999). The development of biotechnological methods for utilization and treatment of diluted manure streams. Wat. Sci. Technol., 40(1), 223-229. Kalyuzhnyi, S., Sklyar, Y., Rodriguez, J., Archipchenko, I., Barboulina, I., Orlova, 0., Epov, A., Nekrasova, Y., Nozhevnikova, A., Kovalev, A., Derikx, P. and Klapwijk, A. (2000). Integrated mechanical, biological and physico-chemical treatment of liquid manure streams. Wat. Sci. Technol., 41(12), 175-182.

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