Copyright @ 2003 by Humana Press Inc.All rights of any nature whatsoever reserved.0273-2289/03/109/0077/$20.00

Sustainable Treatment and Reuseof Diluted Pig Manure Streams in Russia

From Laboratory Trials to Full-Scale Implementation

SERGEY KALYUZHNYI,*,2 VLADIMIR SKLYAR,1

ANDREY Epov,1IRINA ARKHIPCHENKO,2

IRINA BARBOULINA/ OLGA ORLOVA,2

ALEXANDER KOVALEV,3 ALLA NOZHEVNIKOVA,4

AND ABRAHAM KLAPWIJK5

'Department of Chemical Enzymology, Chemistry Faculty,Moscow State University, 119899 Moscow, Russia,

E-mail: svk@enz.chem.msu.ru; 21nstitute of Agricultural Microbiology,Podbelsky shosse 3, 189620 St. Petersburg-Pushkin 8, Russia;

3 Russian Institute of Agriculture Electrification, 109456 Moscow, Russia;

41nstitute of Microbiology, Russian Academy of Sciences,117811 Moscow, Russia;

and 5Subdepartment of Environmental Technology,Wageningen University, 6700 EV Wageningen, The Netherlands

Abstract

This article summarizes the results obtained during the laboratory andpilot development of integrated biologic and physicochemical treatment andreuse of diluted pig manure streams. The application of a straw filter was aneffective means to separate the solid and liquid fractions of raw wastewaterand resulted in the removal of a significant part of the dry matter, totalnitrogen, and phosphorus (65,27, and 32%, respectively). From the filtrategenerated, 60-80% of the total chemical oxygen demand (COD) was removedin an upflow anaerobic sludge bed reactor operating at 15-30°C. Ammoniawas efficiently eliminated (>99%) from the anaerobic effluents using Urallaumantite as an ion exchanger. However, the nitrogen-content of the zeolitewas too low to consider this method of ammonia removal economically fea-sible. The phosphate precipitation block, consisting of stripper of CO2 andfluidized-bed crystallizator, was able to decrease the concentration ofsoluble phosphate in the anaerobic effluents up to 7-15 mg of phosphate/L.The application of aerobic/anoxic biofilter as a sole polishing step wasacceptable from an aesthetic point of view (the effluents were transparent

. Author to whom all correspondence and reprint requests should be addressed.

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78 Ka/yuzhnyi et a/.

and almost colorless and odorless) and elimination of biochemical oxygen Idemand (the resting COD was hardly biodegradable). However, the effluent i

.; nutrient concentrations (especially nitrogen) were far from the current stan-, dards for direct discharge of treated wastewater. We discuss the approaches

for further improvement of effluent quality. Finally, we provide an outlineof a full-scale system that partially implements the laboratory- and pilot-scale results obtained.

Index Entries: Integrated system; nutrient removal; phosphate precipita-tion; pig manure wastewater; straw filter; upflow anaerobic sludge bed ,reactor; zeolite. !

Introduction

In Russia, according to the available statistics, on January 1,1999, therewere, respectively, 8.575,17.381, and 210.810 million pigs, cattle, and poul-

.I try (Table 1) (1). Taking into account the average figures presented injl Table 1, the yearly produced manure can be estimated as 382.7 million t" (as concentrated livestock wastes). However, in the Soviet Union, breeding

of agricultural animals has been developed on an industrial basis, and! Russia has inherited the majority of the facilities. As a result, currently,I e.g., almost one quarter of all pigs are handled on huge complexes (in total

i:i 33) having a capacity for fattening 54,000-216,000 of the animals. However,,":i as a result of the flushing technology used for cleaning, these complexes!' produce yearly about 30 million t of pig manure wastewater containingJ'i' only 2-2.5% total solids. Although these complexes are equipped with

aerobic treatment plants, their 30-yr exploitation has demonstrated a com-, ; plete failure of this technological approach. Often the aerobic systems work

1 f' (if they do) unsatisfactorily owing to frequent overloading with high-I strength manure, and, therefore, the complexes are responsible for the

severe pollution of soils, groundwaters, rivers, and lakes in the surround-ing areas. In addition, such a practice leads to the loss of manure and itsfertilizer potential, a serious problem considering the current lack of organicfertilizers in Russia and an exhaustion of soils in most regions (3).

A possible solution for sustainable utilization and treatment of suchdiluted manure streams is the preliminary mechanical separation of solidand liquid fractions followed by separate biologic and physicochemicaltreatment of both fractions. Using this approach, treatment can be focusednot only on environmental protection but also on reutilization of the valu-able components comprising manure wastewater. This approach is thebasis of two consecutive joint Russian-Dutch projects: (1) "the develop-ment of biotechnological methods for manure treatment focused onfertiliser production" (1996-1998); and (2) "the development of integratedanaerobic-aerobic treatment of liquid manure streams with maximisationof production of valuable byproducts (fertilizers, biogas) and re-utilisationof water" (1999-2001). The ideology and main directions of the researchactivities within these projects are represented in Fig. 1. Various steps of

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Treatment and Reuse of Pig Manure Streams 79

Table 1Livestock and Waste Production in Russia

(without nonmarketable breeding animals) (1)

Average productionof manure Estimated yearly

Number of heads (t/[head.yr]; manure productionAnimals (million) % humidity) (2) (million t)

Pig 8.575 2.4 (87.5) 20.6Cattle 17.381 20 (90) 347.6Poultry 210.810 0.069 (73-76) 14.5Total 382.7

a r

~J--.mc, ""'D """ E-.

t .. r NO.- Discharge to

Re-use for hydraulic wash-out surface waters

Fig. 1. Proposed scheme of integrated liquid manure treatment/reutilization.A, farm (manure production); B, separation of solids/liquid; C, composting of solids;D, final form of fertilizer; E, anaerobic elimination of major part of chemical oxygendemand (COD) (and nitrate if necessary); F, physicochemical removal of nutrients;G, biologic elimination of resting biochemical oxygen demand (BOD) and nutrients.

this integrated treatment scheme were investigated on laboratory and pilotlevels (3-9). This article summarizes the results obtained and gives anoutline of a full-scale system that partially implements them.

Materials and MethodsWastewater

The raw manure wastewaters (RMWs) were taken directly from thepig farms using flushing technologies for cleaning and located in the Mos-cow, St. Petersburg, and Vologda regions. Some of the wastewater charac-teristics are presented in Table 2.

Laboratory Installations

Upflow Anaerobic Sludge Bed ReactorsThe laboratory reactors (diameter: 6.8 cm; height: 85 cm; total working.

volume: 2.6 L) were made from transparent plastic and seeded with floccu-lar anaerobic sludge originating from a previous research study (3). The oper-ating temperatures were 29-30 or 17-20°C. The reactors were fed withstraw-filtered pig manure wastewater in Moscow.

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Table 2Range of Variation in Some Characteristics of Raw Pig Manure Wastewater"

Parameters Moscow St. Petersburg Vologda

OM (g/L) 10-15 12-36 15-20COO (g/L) 11-17 15-43 15-25

totCOOss 4.8-5.9 NO NOCOOcol 1.9-4.2 NO NOCOO.a! 4.2-7.2 NO NOTotal nitrogen (g/L) 0.61-0.91 1.21-2.20 1.0-2.0N-NH3 (g/L) 0.29-0.65 0.98-1.45 0.5-0.9Total phosphorus (g/L) 0.19-0.25 0.2-0.49 0.2-0.26P-PO4 (g/L) 0.17-0.21 0.19-0.23 0.15-0.18pH 6.6-7.5 6.2-8.5 6.5-7.5

aND, not determined.

Ion-Exchanger Columns

Ammonia removal from anaerobic effluents was investigated usingcolumns packed with 300 mL of zeolite (Urals laumantite). Hydraulicretention time (HRT) of the anaerobic effluent in the columns was main-tained at 4 h throughout all the experiments.

Nutrient Precipitation

The feasibility of simultaneous removal of ammonia and phosphatefrom anaerobic effluents via their precipitation in the form of insolubleminerals was investigated in batch vessels by pH adjustment to the alkalivalues performed by natural aging, CO2 stripping, and NaOH dosing asdescribed in ref. 4. In every run, the solution after precipitation was centri-fuged before analysis.

Biofilter

The reactor was made from glass, packed with road metal (workingvolume of 0.7 L), and used as a continuous nitrifying reactor as well as analternating aerobic/ anoxic reactor for treatment of the anaerobic effluentsat ambient laboratory temperatures (17-20°C). In the latter case, the regimeof its operation was as follows: During aerobic phase (duration: 20 or

j 30 min), the feeding was stopped, while air at a flow rate of 1 L/min waspumped through an external loop of the biofilter. Aeration was switchedoff during the anoxic phase (duration: 30 or 40 min), while the continuousfeeding was restored and the high recycle rate of effluent (20 L/h) wasapplied to ensure an adequate mixing in the biofilter. A programmablemultichannel timer controlled all three pumps used. Additionally, in themiddle of the external loop, an electronic sensor (Datchik, Russia) wasinserted for online monitoring of soluble oxygen. The electric signal fromthis sensor was transferred to a programmable data logger system. Thedata were recorded every 2 or 30 s and were averaged (when necessary)over 3-min intervals. A personal computer programmed to function as a

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Treatment and Reuse of Pig Manure Streams 81

terminal emulator was used to communicate with the data logger. Second-ary sludge from Kur'yanovskaya municipal aeration station (Moscow) wasused as the seed sludge for formation of the attached biofilm.

Pilot Installations

Straw FiltersTwo installations consisting of tanks with a rack to retain a randomly

packed wheat straw were constructed. The straw filter in St. Petersburg hadthe following parameters: IS-kg straw weight, 0.52-m2 cross-section, 0.5-mheight, 0.26-m3 volume. The straw filter in Moscow had approximately fivetimes less working volume with a similar cross-section/height ratio andstraw weight of 3 kg. The other details are given in ref. 9.

Upflow Anaerobic Sludge Bed ReactorThe up flow anaerobic sludge bed (UASB) reactor was made from

transparent plastics and had the following size: 22.6-cm2 cross-section(rectangular), 206-cm height, 44.6-L working volume. For experiments inSt. Petersburg, it was seeded with 10L of anaerobic sludge originating froman anaerobic digester treating sewage sludge (Moscow). The RMW wasdecanted and filtered through a straw filter before being used as an influentfor the U ASB reactor. After finishing the trials in St. Petersburg, the reactorwith the sludge was kept unfed in a cool room for 6 mo. Then it was trans-ferred to the pig complex Nadeyevo (Vologda) to assess its performance fortreating a liquid fraction of RMW obtained after separation of solids onvibro sieves.

Phosphate Precipitation Block

The phosphate precipitation block (PPB) consisted of air stripper(diameter: 20 cm; height: 20 cm; working volume: 6 L) for CO2 removal toincrease pH and fluidized-bed crystallizator (FBC) 7.8-cm diameter,105-cm height, 5-L total volume) for crystallization of phosphate mineralssuch as struvite (MgNH4PO4) and hydroxyapatite (Cas[PO4]30H). Bothreactors were made from transparent plastics. The FBC was initially filledwith 1 kg of washed sand (0.25- to 0.5-mm fraction) as a source of nuclei to

I promote phosphate crystallization from supersaturated effluents of thestripper. The fluidization was performed using an airlift loop. This blockworked in line with the UASB reactor during pilot trials in St. Petersburg.Other details are given in ref. 5.

BiofilterThe biofilter was made from transparent plastics and packed with

road metal (0.5- to 2-cm fraction). It had the following size: 13-cm diameter,145-cm height, 19-L working volume) and functioned in alternating aero-bic/ anoxic regime for treatment of the FBC effluent. During the aerobicphase (duration: 20 or 30 min), the feeding was stopped, while air at a flowrate of 5 L/min was pumped through an external loop of the biofilter.

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82 Ka/yuzhnyi et a/.

Aeration was switched off during the anoxic phase (duration: 30 or40min),while the feeding was performed for 5 or 10 min, and the high recycle rateof effluent (20 L/h) was applied to ensure an adequate mixing in thebiofilter. A programmable multichannel timer (with total time cycle of 1 h)controlled all three pumps used. Secondary (nitrifying) sludge from thewastewater treatment plant of the pig complex Vostochnyi (Leningrad

,1 province) was used as seed sludge for formation of the attached biofilm.: : The excess sludge was periodically withdrawn from the top of the biofilter.

I. It worked in line with the UASB reactor and PPB during pilot trials inSt. Petersburg. All other details are given in refs. 4 and 6. i

'Analyses: All analyses were performed using standard methods (9) or as I

: described previously (3-8).

Results and Discussion

Application of Straw Filters for Separation of Manureinto Solid and Liquid Fractions (step 8)

Separation into solid and liquid fractions is an important element ofliquid manure handling in Russia (3). Currently, it is performed by appli-cation of sieves and centrifuges. However, both methods are costly, and inRussian agriculture, there is a need to develop less expensive alternativesgiving byproducts suitable for reuse. Based on the Flemish experience witha pig slurry separation using straw filters (10), we tested this method underRussian conditions.

Typical dynamics of filtrate quality during the startup of the strawfilter in St. Petersburg are shown in Fig. 2. After 3.5 h of operation, the strawfilter was able to remove from the RMW 97, 79, 75, and 45% of the totalsuspended solids (TSS), COD, phosphorus, and nitrogen, respectively.An integrated mass balance of the straw filter for a working cycle (4 d) ispresented in Fig. 3. From these data, one can conclude that the systemensures a removal of 83,32, and 27% of dry matter (DM), total phosphorus,and nitrogen, respectively. These cumulative figures are inferior to thoseobtained during the startup period, possibly owing to the partial solubi-lization of entrapped matter on the straw filter (see curve of ammonia inFig. 2). Thus, to minimize these unwanted processes, the duration of aworking cycle for a straw filter should be decreased to 2 to 3 d (if possible).Testing of the straw filter in Moscow where the RMW was more diluted(Table 2) also showed a significant reduction (up to 60%) in TSS and colloi-dal COD (COD coJ in the filtrate (4). However, straw filtration had a minimalinfluence (what it is quite obvious) on concentrations of soluble compo-nents such as volatile fatty acids (VFA), ammonia, and phosphate.

Thus, application of straw filter was an effective measure for separa-tion of pig manure into liquid and solid fractions. Moreover, this technique ;"

,I Applied Biochemistry and Biotechnology Vol. 709,2003 ,

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Treatment and Reuse of Pig Manure Streams 83

40 2,5~ ~ ---Ntot '"-N-NH3~ 32 --- TSS '"- CODtot . 2,0 ~ Ptot= =

'. ~~ 24 ~ 1,5 bf fd 16 a ~ 1 0~ = ,OJ ~

g 8 g 0,5u u

0 0,0

0 60 120 180 240 0 60 120 180 240Filtmtion time, miD Filtration time, miD

Fig. 2. Typical dynamics of filtrate quality during startup of straw filter.

. Entrap~d . Filtrate10080

c 60~c 40

20

0

Mass DM Ntot Ptot

Fig. 3. Distribution of mass, OM, total nitrogen, and phosphorus between entrappedmatter in straw filter and filtrate (duration of operation is 4 d).

allowed direct use of straw with entrapped manure matter for composting(discussed next).

Composting of Straw with Entrapped Manure Matter (steps C and 0)and Compost Quality

The straw with the entrapped manure matter was a subject of exten-sive composting (6-mo duration). The details are given in refs. 7 and 8.The quality of compost obtained was tested with ryegrass in greenhousesusing a podsolic soil. The results showed a good efficiency of the compostsapplied; the crop was increased by 61-95% concerning control without anyfertilizers (8).

Elimination of COO Using UASa Reactor (step E)

Laboratory ExperimentsThe data for straw-filtered manure wastewater (SFMW) were exten-

sively published (3,4,6). The optimal results are summarized in Table 3.It can be seen that in spite of a 10°C drop in temperature, the performanceof sub mesophilic treatment was comparable with mesophilic treatmentregarding total COD (CODtoJ removal under similar HRTs and organicloading rates (OLRs). However, for both regimes, the ammonia concentra-tions increased in the effluents owing to hydrolysis of proteinaceous sub-

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Treatment and Reuse of Pig Manure Streams 85

stances in the SFMW (Table 3). The concentration of phosphate substan-tially dropped during treatment of SFMW. This was attributed to partialprecipitation as whitish deposits (presumably calcite, CaCOy hydroxyapa-tite, Cas[PO 4]30H; and struvite, MgNH4PO J, which were clearly visible onthe reactor walls and in the internal gas sludge separation device (4).Note that the COD removal was higher compared to that in the availableliterature about treatment of pig manure in UASB-like reactors (11). How-ever, such exhaustion of easily degradable COD (e.g., VFA) in the anaero-bic effluents might create problems for subsequent biologic nitrogenremoval.

Pilot Experiments

Because the SFMW in St. Petersburg had a higher strength and theseed sludge was poor quality, the pilot trials were started under higherHRT compared to the laboratory experiments (Table 3). When the HRTwason average 3.5 d, resulting in an average OLR of 1.7 g of COD/(L-d), theCODtot removal was 45% while removal of suspended solids (SS), and col-loidal and soluble COD (COD.oJ fractions was 69,59, and 38% (on average),respectively (Table 3). In spite of a large fluctuation in influent pH,the effluent pH was rather stable, about 7.5. Specific methane productionwas also a subject of some variations and accounted (on average) for0.23 nLI (L-d). This value is somewhat below the theoretically expected one(0.27 nL/[L-d]) taking into account the observed COD removal (Table 3).The discrepancy can be mainly attributed to entrapment of some part of theundigested SS by the reactor sludge bed. As expected, the ammonia con-centrations slightly increased and the concentrations of phosphate sub-stantially dropped during the anaerobic treatment of SFMW (Table 3), forreasons similar to those in laboratory experiments.

After a decrease in HRT to on average 2 d, resulting in an increase inOLR to 5 g of COD I (L-d) (on average; Table 3), the CODtot removal stepwiseincreased to about 70%. This was the result of increased removal of COD

Jcoand COD.oJ fractions (on average 74 and 63%, respectively) compared to theregime with an HRT of 3.5 d (Table 3). By contrast, a slight decrease in SSremoval was detected owing to increased washout of sludge and otherentrapped particulate matter clearly observed throughout the last period ofthe pilot trials. In spite of acidic influents fed to the reactor, the effluent pHwas stabilized around 7.2 (Table 3) owing to VF A consumption and ammo-nia production. A phenomenon of substantial total phosphorus and par-ticularly phosphate removals was also observed during this period (Table 3).

The pilot trials in Vofogda did not reveal significant differences com-pared with the trials in St. Petersburg, and all the accumulated data servedas a basis for designing a full-scale UASB reactor at pig complex Nadeyevo,Vologda province (discussed later).Removal of Ammonia from Anaerobic Effluents by Zeolite (step Fl)

It was found (4) that 1 vol of Urals laumantite (particle size of 1 to2 mm) could treat at least 10 vol of anaerobic effluent (HRT of 4 h), reducing

Applied Biochemistry and Biotechnology Vol. 109,2003I~

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86 Ka/yuzhnyi et a/.

ammonia concentrations from 360 to 1-5 mg of N /L. However, the chemi-cal analysis showed that 1 kg of completely saturated zeolite containedonly 3.6 g of ammonia and 5.3 g of total nitrogen. Such a low nitrogencontent restricts its application as a fertilizer and this type of zeolite as aneconomically attractive ammonia adsorbent. One possible solution may bea chemical regeneration of zeolite for multiple (cyclic) uses. Nitric acid hasbeen proposed as a regenerating agent with the aim of producing a liquidfertilizer (ammonia nitrate). Another solution could also include a searchfor ion exchangers with better ammonia adsorption properties than Urallaumantite. Clinoptiolite and wollastonite (if locally available) are amongthe candidates to be considered (12).

Removal of Phosphate and Ammonia from Anaerobic Effluentsvia Precipitation (step Fl)

In addition to ammonia and phosphate, the anaerobic effluents con-tain magnesium and calcium (usually at concentrations ~ mM). Thus,struvite and hydroxyapatite precipitation can be initiated by adjusting thepH to the optimal supersaturating value, which is above 9.0 (13). However,partial precipitation of these minerals likely occurred in the UASB reactor(see step E) that had an effluent pH of about 7.5 (Table 3). Effluent pH canbe further increased by natural aging, air stripping of CO2, or base dosing(13). Our experiments with the first two methods indeed showed a substan-tial increase in pH (especially during air stripping) in the anaerobic efflu-ents accompanied by a noticeable decrease in phosphate and ammoniaconcentrations: 23 and 7% (natural aging) and 66 and 29% (air stripping),respectively (4). Comparable (with air stripping) nutrient removal from theanaerobic effluents was achieved using base dosing accompanied by addi-

! tion of magnesium (4). However, base/magnesium dosing and batch: precipitation are not very convenient from a technological point of view.i Thus, we have developed a continuous reagentless process based on air

stripping similar to that described by Battistoni et al. (14,15).The results of continuous, pilot-scale phosphate precipitation pro-

moted by air stripping of CO2 to increase pH and crystallization in the FBCare presented in Table 4. The total HRT in the PPB was initially set as -1 d(-0.6 d in the stripper and -0.4 d in the FBC). During d 0-32, this blockdemonstrated a very good efficiency regarding phosphate removal-84%(on average; Table 4)-ensuring effluent phosphate concentration below

i 10 mg/L. Some drop in ammonia concentrations was also detected.In addition to suspected struvite formation, some losses of ammonia prob-ably occurred owing to its stripping into the gas phase at pH values >8.0,which were usually observed in the precipitation block. Furthermore, bio-logic nitrification of ammonia was gradually developed in the FBC; theeffluents contained 200-300 mg ofN-NO3 during d 35-45 (data not shown).Since occurrence of ammonia nitrification, which became almost completeduring d 38-45 and led to a drop in pH below 8.0, had a deterioratingimpact on the phosphate removal, the total HRT for the precipitation block

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Treatment and Reuse of Pig Manure Streams 87

Table 4Operational Parameters and Efficiency of PPB Treating Anaerobic Effluents (5)"

Parameter Period 1 (d 0-32) Period 11-2 (d 47-75)HRT (d) l' ' 0.25

Influent P-PO4 (mg/L) 50:t: 21 57:t: 11Effluent P-PO4 (mg/L) 7:t: 3 15:t: 4P-PO4 removal (%) 84:t: 12 73:t: 10Influent N-NH3 (mg/L) 896 :t: 348 916 :t: 246Effluent N-NH3 (mg/L) 560 :t: 217 747:t: 213N-NH3 removal (%) 37:t: 13 32:t: 9

"Means:!: SO.

was reduced to -0.25 d at d 47. This resulted in a gradual increase in phos-phate removal to the average value of 73%, with the average effluent phos-phate concentration of 15 mg/L for period 11-2 (Table 4). In addition,ammonia nitrification almost stopped; only negligible concentrations ofnitrate and nitrite were observed in the effluent during this period (data notshown). The overall removal of ammonia (presumably owing to struviteprecipitation and stripping) was 32% (Table 4).

Removal of Nutrients from UASB and PPB EffluentsUsing Aerobic/Anoxic Biofilter (step G)

Laboratory ExperimentsSince the PPB effluents were available only during pilot trials, all the

laboratory experiments were performed with the anaerobic effluents thatwere similar to the PPB effluents regarding nitrogen concentrations. Somecharacteristics of the anaerobic effluents used are listed in Table 3 (underheading "Laboratory experiments") and Table 5. A successful startup of thebiofilter in a nitrifying mode was achieved using an HRT of 2 to 3 d and anOLR of 0.4-0.7 g of COD / (L.d). Ammonia and COD removals in the end ofstartup period were higher than 90 and 65%, respectively (4). Prior to start-ing an alternating aerobic/ anoxic mode of biofilter operation, the actual,basic (endogenous), and nitrifying respiration rates were assessed. Theywere 49.1 :!: 4.7, 13.7:!: 0.2, and 34.3:!:: 1.4 mg of °2/(L.h), respectively (4).Thus, the respiration rate for the oxidation of easily biodegradable COD inthe anaerobic effluent accounted for 14.8:!: 3.1 mg of °2/(L.h) or 360:!:70 mg of COD / (L.d). Taking into account the planned ammonia load on abiofilter (about 300mg ofN-NH4+ /[L.d]), this quantity of easily biodegrad-able COD cannot fully fulfill denitrification requirements. In spite of thislimitation, the alternating aerobic/ anoxic experiment was started in orderto assess not only nitrogen but also phosphorous and COD removals in realreactor conditions. Note that the denitrification proceeded almost immedi-ately after switching the biofilter to alternating mode of operation.The typical dynamics of COD, soluble oxygen, nitrate, and ammonia

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88 Ka/yuzhnyi et a/.

Table 5Performance of Laboratory Biofilter Treating UASB Reactor Effluents (6)-

COD Ammonia Nitrate PhosphateParameter (g/L) (mg N /1) (mg N /1) (mg P /1)

HRT: 1.0.t 0.1 d; OLR: 0.87.t 0.10 g COD/(L.d);

aerobic phase: 30 min; anoxic phase: 30 min

Influent 0.869 .t 0.097 336 .t 53 0 70 .t 10Effluent 0.353 .t 0.057 77.t 18 175 .t 29 30 .t 9Removal (%) 66.t 7 77.t 5 25 .t 3b 57.t 17

HRT: 1.01 .t 0.04 d; OLR: 0.75.t 0.04 g COD/(L.d);

aerobic phase: 20 min; anoxic phase: 40 min

Influent 0.741.t 0.026 246.t 110 0 40.t 1

Effluent 0.301 .t 0.021 42 .t 1 128 .t 6 21 .t 1Removal (%) 70.t 1 81 .t 8 31 .t 5b 48 .t 2

-Means:t SD.

lI"fotal nitrogen removal

-.-N-N03 ---N-NH3 -02 -o-COD- 190 85 4 480'Ob - ~e 185 ~ e 3 460 ~0" 80 ..,. .:, 440 eZ 180 :c ~ 2 420 ci

I 75 ;zr - 0Z 175 Z :a 1 400 u

0170 70 rJ) 0 380

0 30 60 90 120 0 30 60 90 120Tinx:, mill Time, miD

Fig. 4. Dynamics of soluble oxygen, COD, nitrate, and ammonia concentrationsduring alternating operation of biofilter (influent CODtot: 790 mg/L; influent ammo-nia: 344 mg of NIL; HRT: 1.13 d).

concentrations during several aerobic/ anoxic phases are shown in Fig. 4.Some results of laboratory biofilter performance are presented in Table 5.Surprisingly, the biofilter showed good removal of phosphate-about 50%.It is likely that some chemical precipitation of phosphate minerals occurredbecause the sludge had an increased mineral content (data not shown).Nitrification of ammonia was about 80%, while denitrification owing toshortage of easily biodegradable COD was rather poor, resulting in totalnitrogen removal of only 25-30% (Table 5). The effluent COD concentra-tions slightly fluctuated around 0.3 g/L throughout the entire experiment.It is likely that this concentration represents a hardly biodegradable(under neither anaerobic nor aerobic conditions) fraction of COD in the pigmanure wastewater.

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Treatment and Reuse of Pig Manure Streams 89

Table 6Operational Parameters and Efficiency of Biofilter Treating Effluents from PPBa

Period I Period 11-1 Period 11-2Parameter (d 0-32) (d 33-46) (d 47-87)

Aerobic phase (min) 30 20 30Anoxic phase (min) 30 40 30HRT (d) 3.3:t 0.6 3.3:t 0.1 2.0:t 0.4OLR (g COD/[L.d]) 0.86:t 0.48 1.04:t 0.16 1.39:t 0.22ALR (mg N-NH3/[L.d])b 168:t 118 28:t 22 365:t 62Influent CODtot (g/L) 2.93:t 0.7 3.55:t 0.29 3.15:t 0.55Effluent CODtot (g/L) 0.72:t 0.17 0.45:t 0.05 0.82:t 0.12Total COD removal (%) 74:t 11 85:t 5 71:t 7Influent CODss (g/L) 0.52:t 0.33 1.74:t 1.34 0.54:t 0.44Effluent CODss (g/L) 0.05::!: 0.01 0.02:t 0.01 0.12::!: 0.09CODssremoval (%) 84:t 11 99::!: 1 79:t 11Influent CODcol (g/L) 0.31 :t 0.21 0.45 ::!: 0.31 0.70:t 0.60Effluent CODcol (g/L) 0.23::!: 0.15 0.04:t 0.03 0.15::!: 0.10CODcOl removal (%) 40::!: 33 86:t 11 63:t 20Influent CODsol (g/L) 2.10:t 0.96 2.36:t 0.22 1.89:t 0.96Effluent COD sol (g/L) 0.43:t 0.19 0.39::!: 0.04 0.56:t 0.11CODso1 removal (%) 79:t 10 83:t 2 68::!: 13Influent pH 8.5:t 0.5 7.8::!: 0.6 7.9:t 0.2Effluent pH 8.2::!: 0.5 8.2:t 0.3 7.9::!: 0.2Influent N-NH3 (mg/L) 560:t 217 94:t 34 738:t 97Effluent N-NH3 (mg/L) 134::!: 79 14:t 10 448:t 115N-NH3 removal (%) 75:t 8 84:t 10 39:t 10Effluent N-NO3 (mg/L) 140::!: 115 195::!: 130 17:t 14N-NO3 removal (%)c 65:t 24 45:t 31 94:t 5Total nitrogen removal (%)d 49:t 21 42:t 28 37:t 12Effluent total P (mg/L) 31:t 11 31:t 11 21:t 10Effluent P-PO4 (mg/L) 18::!: 2 20:t 2 18::!: 6

"Means :t: SD.b ALR, ammonia loading rate.'Calculated as follows: (1- [N-NOj /([N-NO3L + [N-NH.L - [N-N~]~) x 100.dCalculated as follows: (1- ([N-NOJq + [N-~1q)/([N-Nb31n + [N-NH3];n)} X 100.

Pilot ExperimentsThe results obtained with the PPB effluents are presented in Table 6.

During period I (d 0-32), when duration of anoxic and aerobic phases was30 min each, the average HRT was 3.3 d while the average OLR was 0.86 gofCOD/(L.d) (Table 6). TheaverageCODtotremoval was 74%, although theremoval of individual COD fractions was not uniform-84, 40, and 79%(on average) for 55, colloidal, and soluble matter, respectively. In spite ofsignificant variations in the influent concentrations, the CODtot effluentconcentrations were fairly stable, slightly oscillating around 0.72 g ofCOD IL (Table 6). The efficiencies of nitrification and denitrification were75 and 65% (on average), resulting in average inorganic nitrogen removal

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90 Kalyuzhnyi et al.

of 49%. A more than double increase in phosphate concentrations in thebiofilter effluents compared with those of PPB (see Tables 4 and 6) waslikely owing to the dissolution of the small phosphate precipitates enteringthe biofilter with the influents (these small precipitates were not accountedfor during soluble phosphate analysis because the samples were centri-fuged before analysis).

Because of the occurrence of ammonia nitrification in the PPB result-ing in the low influent ammonia concentrations entering the biofilter, theduration of anoxic phase ofbiofilter operation was increased to 40 min andthat of aerobic phase was decreased to 20 min, keeping the average HRT onthe same level of 3.3 d during period II-I (d 33-46; Table 6). In spite of anincrease in the average OLRto 1.04 gofCOD/(L.d), the CODtotremoval aswell as COD removal of individual COD fractions also increased (com-pared to period I), resulting in average effluent concentrations of total andCODso1 of 0.45 and 0.39 glL, respectively, approaching the biodegradabilitylimit of the pig manure wastewater. Although the effluent ammonia con-centrations were relatively low, about 14 mg of NIL, the total nitrogenremoval was on average 42% (period II-I; Table 6) owing to insufficientdevelopment of the denitrification process (lack of biodegradable COD),which resulted in high effluent nitrate concentrations (195 mg of NIL on

average).To improve nitrate removal, the HRT was decreased to about 2 d

(period 11-2; Table 6) while duration of anoxic and aerobic phases wasequalized to 30 min each. As a result, the average OLR increased to 1.39 gof COD/(L-d), but the COD tot removal and COD removal of individualCOD fractions decreased with respect to period II-I, being comparablewith those for period 1 (Table 6). The better availability of easily biodegrad-able COD immediately resulted in an almost complete nitrate removal, andthe average effluent nitrate concentration accounted for 17 mg of NILduring this period. However, this operation regime had a detrimental effecton nitrification-the average ammonia concentration accounted for 448 mgof NIL. Besides the higher ammonia loading rate applied (less ammoniastripping in the PPB), this was probably owing to a decrease in concentra-tion of the autotrophic nitrifying bacteria in the biofilter, which wereoutcompeted by heterotrophic microflora under the elevated OLR imposedon the system during period 11-2.

Conclusion

The application of a straw filter was an effective means of separatingthe solid and liquid fractions of diluted pig manure wastewater andresulted in the significant removal of CODtot' nitrogen, and phosphorus(in our experiments 80, 27, and 32%, respectively). The compost obtainedfrom the straw-entrapped OM was an effective fertilizer, increasing thecrop of ryegrass in greenhouses by 61-95%.

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Treatment and Reuse of Pig Manure Streams 91

100 1 . CODtot ,. Ntot 0 Ptot~ Id' 80 ~0

.it: 60-c

g 408.~ 20 -llJi!!~ 1'(i;,

~ 0 .,RMW SF UASB PPB BF

Fig. 5. Relative decrease in CODtot' nitrogen, and phosphorous concentrations aftereach treatment step. SF, straw filter; BF, biofilter.

From the filtrate generated, up to 70-80% of the COD could beremoved in the UASB reactor operating even under submesophilic condi-tions (15-20°C). Ammonia was efficiently removed (>99%) from theanaero-bic effluents using Urallaumantite as an ion exchanger. However, thenitrogen content of the zeolite was too low to consider this method ofammonia removal economically feasible.

The PPB was able to decrease the concentration of soluble phosphatein the anaerobic effluents up to 7-15 mg of phosphorus/L, but measuresshould be taken to prevent entrance of small phosphate precipitates intothe biofilter, where they can dissolve, increasing soluble phosphate con-centrations in the final effluents.

The application of aerobic/ anoxic biofilter as a sole polishing step wasacceptable from an aesthetic point of view (the effluents were transparentand almost colorless and odorless) and BOD elimination (the resting CODwas hardly biodegradable). However, the effluent nutrient concentrations(especially nitrogen) were far from the current standards for direct dis-charge of treated wastewater. Possible remedies include usage of some partof the nontreated liquid fraction of RMW to fulfill the denitrificationrequirements in biodegradable COD or application of posttreatment stepssuch as constructed wetlands.

Figure 5 summarizes the averagf!data showing decreases in CODtot'nitrogen, and phosphorous concentrations for the RMW after each treat-ment step in pilot investigations. It is interesting to analyze the possibilityof phosphorous recovery in the proposed scheme of RMW. Approximatelyone third of phosphorus is retained with solid fraction after straw filterfiltration and can be reused in the form of compost. An additional 18% isprecipitated inside the UASB reactor while 36% can be recovered fromanaerobic effluents using the PPB. The phosphate minerals (presumablystruvite and hydroxyapatite) formed have a prospective use as fertilizers oras raw material for the phosphate industry (e.g., the price of magnesium-ammonia phosphate in Russia is $100-150/ t). Based on the data of pilot-scale trials presented in this article, the potential of phosphate recovery

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92 Kalyuzhnyi et al.

, from overall flow of manure wastewater from Russian pig complexes canI: be estimated as 4.3 thousand tons (as phosphorus) per year.

Outline of Full-Scale Implementation

The developed technology is in the implementation stage now at pigcomplex Nadeyevo (Vologda province). This complex, fattening 54,000 pigsper year, produces daily 1600-1700 m3 of RMW. The wastewater treatmentplant was constructed 20 yr ago and includes two-step aeration tanks(not designed for nutrient removal). It stopped operation in the mid-1990sbecause of enormous energy expenses for aeration as well as the amortiza-

,[ tion of pumping equipment and other infrastructure. Since that time, the, RMW after separation of solid fraction on vibro sieves was directly dis-

charged into sewerage of the city of Vologda. However, as the result ofoverloading of this municipal treatment plant, such a discharge of the FMWwithout substantial reduction of COD, nitrogen, and Phosphorous con-

totcentrations will be banned at the end of 2002. To solve this problem, themanagement of complex Nadeyevo together with the governmentalauthorities of Vologda province have decided to reconstruct the waste-water treatment plant with partial implementation of the scheme depictedin Fig. 1.

According to the reconstruction plan (the overall investments areestimated as $1,000,000), a full-scale UASB reactor (working volume of1000 m3) has already been designed and will be commissioned in 2002.This reactor will be inserted after installment of vibro sieves and primarysettlers (which will be optimized) and will treat -70% of settled SFMW. Theanaerobic effluents will be then treated in the PPB (this block is scheduledto be built in 2003) in order to reduce the phosphorous content in them andmitigate scaling problems caused by spontaneous precipitation of phos-phate minerals in the pipelines (this is a continuing problem for wastewatertreatment plants on such complexes). The PPB effluents together with 30%

, of settled SFMW (source of biodegradable COD to fulfill denitrificationi requirements) will then be treated in the existing air tanks. The latter, how-il ever, will be renovated (new pumping equipment and so on) and tuned for1 not only BOD but also nitrogen removal.i Some important parameters of old and new technological schemes for, treatment of the RMW are shown in Table 7. The new technological scheme

undoubtedly has advantages compared with the old one. Namely, itreduces electric energy consumption and sludge production, guarantees a

I:, mu~h better quali~ of treated w.at~~ (especially re~arding nutrient concen-i trahons), and provIdes the possIbilIty of energy (blogas) and phosphorous

recovery.

Acknowledgment

We gratefully acknowledge the financial support of NetherlandsOrganization for Scientific Research (NWO) (grants 96-299971 and 047-07-18).

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Treatment and Reuse of Pig Manure Streams 93

Table 7Basic Parameters of Old and New Technological Schemes

for Treatment of RMW at Complex Nadeyevo (Vologda province)

Parameter Old technology" Proposed technologyb

Quality of treated waterCOD (mg/L) 500-600c 100-300SS (mg/L) 25-30 25-30Total nitrogen (mg/L) 300-350 35-50Total phosphorus (mg/L) 80 30-.,35

Energy consumption I recovery(kWh I d)

Aeration: air flow (m3/h) 17,860 5920Energy consumption 11,424 7584dSludge recirculation 1390 1720

and mixingEnergy production (as heat) 0 27,300

(CH4: --4750 m3 I d)Energy balance -12,814 +18,266

Sludge productionPrimary sludge 9.05 t/d, or 180 m3/d 10.2 t/d, or 204 m3/dAerobic sludge 5.42 tl d, or 542 m3 I d 2.94 tl d, or 294 m3 I dAnaerobic sludge 0 0.98 tl d, or 20 m3 I d

Total 14.5t/d,or720m3/d 14.1t/d,or520m3/dPhosphate recovery (t/d) 0 0.5

"Not in operation now; calculations are made on the basis of data from the mid-1990s.bDesigned to fulfill the limits for direct discharge into sewerage of the city of Vologda.cWithout excess sludge (ideal case, almost never fulfilled).d'fogether with mechanical mixing..

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