Tgp chi Khoa hgc Tnr&ng Dai hoc Cdn Tha Phdn A: Kboa boc Tif nhien. Cong ngh? vd .Moi tnrang. 28 (2013). i
Tap chl Khoa hpc Tru'dng Oai hoc Can Thci website: sj.ctu.edu.vn
CHAT LirONG NlTdC TRONG HE THONG NUOI CA SAC RAN {TRICHOGASTER PECTORUS) THAM CANH KET HOP V d l BEO TAI Tl/ONG {PISTIA STRATIOTES) Dao Quoc Binh', Lam Nguyin Ngpc Hoa' va Ngo Thuy Diim Trang'
'Khoa Mdi trudng vd Tdi nguyen Thiin nhiin, Trudng Dai hoc Cdn Tha
Thong tin chung:
Ngaynhdn: 05/05/2013 Ngdy chdp nhgn: 29/10/2013
Title:
Water quality variation in the integrated system of intensive culture snakeskin gourami (Trichogaster pectorlis) and
•water lettuce (Pistia stratiotes)
Td khda:
Beo Tai tuang, cd Sac ran, dgm. ldn, ty le che phu bi mat
Keywords:
Pistia stratiotes L, Trichogaster pectorlis Regan, nitrogen, phosphorus, surface coverage ratios
ABSTRACT
In the traditional earlhem pond culture, water in intensive Trichogaster pectorlis Regan pond culture needs to be renewed by flushing out directly to the adjacent canals, leading to degradation of aquatic ecosystem In order to reuse excessive nutrients, purify pond water and use surface water more effectively, the floating beds of water lettuce (Pistia stratiotes L) at four coverage ratios of 0, 25, 50 and 75% pond surface area were applied. The concentration of NHj-N in the water body was low in all treatments while TP concentration was higher in the lower coverage ratios of 0 and 25%. Coverage ratios did not affect fish growth except the greatest feeding efficiency in the 25% coverage. During 60 days oj experiment, water in the experimental tanks did not require changing, but water quality was remained within a suitable range for normal growth oj Snakeskin gourami. Therefore, the study helps to maximize efficiency oj water use and utilize nutrients that contributes to protect the environment and to sustainably manage water resource.
T 6 M TAT
Vdi cdch nuoi iruyen thdng. nudc trong ao nudi cd Sgc rdn thdm canh cdn duac thay mdi bdng cdch thdi trirc tiep ra hi thdng kenh rach ddn din su suy thodi cita hi sinh thdi thiiy vifc. Nhdm tdn dung lu(mg dinh duong thua, ldm sach nudc ao nudi cd vd sd dung ngudn nudc mat hiiu qud hon, cdc be ndi thd beo Tai tugng (Pistia stratiotes L.) v&i 4 mirc do che phu 0.
25, 50 vd 75% diin tich bi mdt ao duoc su dyng vd danh gid. Ndng do NHj-N thdp d tdt cd cdc nghiim thirc, trong khi TP cd ndng do cao d ty li che phd thdp 0 vd 25%. Ty li che phu khdng dnh hudng din su tdng trudng cua cd, ngogi trit hieu qua thuc dn cua ty le che phu 25% Id nho nhdl. Trong sudt 60 ngdy nghien citu, khdng cdn thay mrdc cho cd, nhung chdt lugng nudc vdn dugc duy tri trong pham vi cho phep cho cd tdng truong binh thudng. Qua do, tdng hieu qud sir dung nudc vd tan dung dinh duang, gop phdn bdo vi mdi trudng vd qudn ly bin vitng tdi nguyen nudc.
1 GlOfl THIEU
Mfit trong nhiing mfi hinh nufii frfing thiiy sdn bin vihig mang lai hieu qui kinh tl cao d dfing bins sfing Cuu Long (DBSCL) li mfi hinh Vudn- Ao-Chudng-Biogas (VACB) vdi ddi tugng nudi la cd Sac rdn. Tgi Viet Nam, nang sudt nuoi ca Sac
rdn dgt binh qudn 2.5 tan/1.000 m-/vu (Thiiy san Viet Nam. 2011). San lugng ci Sgc ran nudi thim canh cua thi gidi tang tir 21.320 tan nam 1999 den hon 40.000 tin nam 2009, dgt hem 30.000 tin nam 2010 (FAO, 2012). Vdi cdch nuoi fruyin thfing, tugna nudc thai ra tir ao nufii ca Sac ran ra mdi
Tap chi Khoa hoc Tru&ng Dgi hgc Cdn Tho Phdn A- Kboa hgc Tu nhien, Cong nghi va Moi truang: JS '2013i- 64-72 trudng vdn con khi ldn, khoing 20-30% lupng
nudc ao mdi tin thay vi sd ldn thay nudc cung kha thudng xuyen, tir 7-10 ngdy/lan cfao 1 vy nuoi keo dii lir 6-8 tfaang.
Dl hgn chi d nhilm ngudn nuoc mat tir nudc thii ao nudi cd Sac ran vi dim bio sinh trudng tdt cho cd. nghiin ciiu sir dyng be ndi thyc vat kit hgp trong cac be nufii ci Sac ran tuan hodn kin dugc thuc hien nham hgn che xd thii vd tdi sOr dung ngufin nudc vi dinfa dudng frong bl nufii ca tgo sinh khoi thyc vdt.
2 PHU'aNG PHAP NGHIEN CUtJ 2.1 Bo tri thi ngfailm
Thi nghiim dugc bfi fri vi thyc hiln tai Khoa Mfii tnrdng & Tai nguyin Thiin nfaien, Kfau 2, Dai hpc cin Tha frong 2 thdng. Su dung 8 bl composite (200 cm x 70 cm x 30 cm: ddi x rfing x cao) de nudi cd, thi ngfailm dugc bd tri ngiu nfailn voi 4 nghiim thuc vd 2 lan lap lai. Nghiim thiic vdi cac diln tich che phii beo Tai tugng kfaac nfaau lin lugt li 0, 25, 50 va 75% so voi dien tich bl mat eua bl (Hinh 1).
Moi be cd thi tich nudc li 0,40 m' vdi mil dp cd thi ban ddu li 70 con/m'. Cd dupe cho an 2 Idn/ngay bdng thiic an Aquaxcel 7424 dgng vien nfii (40% dgm ciia cong ty thiic in Cargill-Vill Nam) vdi lugng thiic dn ban ddu Id 5% frpng lugng CO thi ca. Sau dd tupng thiic in da dugc dilu chinfa theo khd ning dn ciia cd.
Chpn 30 tai beo gin ddng dgng ve kich cd cho moi kfaung, can frpng lugng beo ciia moi bl tnrde bd tri thi nghiem. Cac tai beo dupe giCr bdi cdc khung lim tir dng nhua PVC G 27 mm, khung cd kich thudc 590 mm x 590 mm va cd 1 ldp luoi bao quanh phia dudi nham franh ci an rl beo vi cac choi non.
Nudc diing dl nuoi ca li chit thii tii tui u biogas pha lodng vdi nudc may tfaeo ty 11 178,5 m^
chii thii biogas/1-000 m' nudc may dya frln kit qud nghiin ciiu ciia Ll Thj Phirong Mai (2010).
Theo ddi lugng nudc bfic hoi 2 lin/tuin va bfi sung them nuoc may Se giiir myc nudc ban diu. Ghi nhdn lugng nudc thim vao.
2.2 Cdc chi tieu theo doi 2 2 1 Chdt luong nudc
Miu nudc dugc thu dinh ky mdi tudn di theo ddi bien dpng chdt tugng nude frong he tfadng nudi theo thdi gian. Thdi gian thu miu tir 7h din 8h sang. Cic chi lieu pH. EC. DO \ a nhiet dp dupe do ngay tgi khu thi nghiem bing may cdm tay. trong khi nong do NH.|-N (dgm amfin), vd TP (tdng lan)
dugc phdn tich bing phucmg phdp salicylate va acid ascorbic tuong iing, dya ttieo quy trinh tllu chudn danh gii nudc vi nudc thdi (APHA et al..
1998).
2.2.2 Beo Tai tugng
Chpn them 30 tai beo gin ddng dang vd kich cfi' vdi beo ldm thi ngfailm, do cfaieu ddi tfadn, rl. cdn frpng lugng thdn, rl tuoi vd khd (sdy d nhi?t dfi 70*'C din frpng lugng khdng ddi), de xde djiih frpng lugng trung binh ciia beo ban dau. Trong thdi gian nghiin eiiu, beo phat frien rat tot vd nhanh.
Sau 21 ngay thu hoach beo dgt 1.
Sau dd, beo dugc tfau faoacfa mfii tudn. Moi be thu hoach ngau nhien 20 tai beo, dim tdng so lugng beo mdi sinh ra, do chilu dai thin re ciia 10 tai beo chpn ngau nfailn, can ttpng lugng tuoi va khd (sdy d nhilt dd 70°C din ttpng lugng khong ddi) ciia tfain rl lit cd beo thu dupe. Cuoi thi nghiim, beo dugc thu hoacfa de tinfa cdc efai lilu sinh trudng nhu sd lugng, ttpng lugng tuoi vi khfi (sdy d nhiet dp 70°C din ttpng lugng khfing ddi), tdc dp tang trudng.
2.2.3 Cd Sgc rdn
Chpn 28 ci ihl cd Sic rdn Trichogaster pectoralis, Regan cd gifing (3,4-3,6 g/con) gan dfing dang vd kich cd, do chieu ddi than, can trpng lugng tfroi ciia timg ci thi vi ghi nhan tdng ttpng lugng cd tfad vio mdi bl, chyp hinh trudc khi bo tri.
Trong qui frinh thi nghiem, ghi nhdn sd lupng ca chit, ghi nhgn frpng lugng tucri ciia thiic dn cho ci dn (hdng ngiy). Cufii thi nghiem, cd dupe thu hogch de tinh cac chi tiiu sinh frudng nhu ttpng lugng, FCR, tdc dp tang tnidng, ty 11 sdng.
Cdc thdng sd theo ddi trin cd dugc tinh todn nhu sau:
Trpng lupng ci tang them (g/bl) = ttpng lugng cd thu hoach (g/be) - ttong luang cd ban diu ig/hi).
Tdc dp tdng tnrdng binh quan theo ngay (%/ngay) = 100*(frpng lugng cd tdng thim (Kg/be)/(frpng luong cd ban diu (Kg/ngay)*so ngiy nudi)).
Toe do tang trudng tuong ddi, SGR (%/ngiy) = 100*(Ln(ttpng lupng c i thu hoacfa) - Ln(trpt^
lygng cd ban dau))/sd ngay nudi.
FCR = trpng lugng tfaiic dn sii dung/frpng lugng ci tang thim.
Hieu qua thiie dn cho dn (%) = 100*(Trpng lugng ci ting thim /frpng lugng thiic an).
Ti le sfing (%) = I00*(s6 ci thu hoach /sd ca ban dau).
T^p chi Khoa hoc Innm^Dni hgc Cdn Tho Pbc'in A Kboa hoc Tu nhien. Cong ngh? vd Moi tnr&ng: 28 (2013)- 64-7
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Tap chi Kboa boc Truong Dai hoc Cdn Tba Phan A Kboa bgc Tw nbien, Cdng nghe vd Mdttni&r^: 2S12013): 64-'2 2.3 Phuong phap xd ly so lilu EC va NHj-N bi dnh hudng bdi ci 2 nhin td ty II . , , ,.- che pfaii vi thdi gian, trong khi tfadng sd nhiet dfi Cac chi lieu chat lugng nuac dugc theo doi ^^^. ^^. ^^ ^- ^ ^ ^ ^ ^. ^ ^ ^ • theo thdi gian vi phan tich phuong sai hai nhan to
(Two-way ANOVA) vdi nhin tfi thu I la ty 11 che Gia tri tnmg binh ciia cdc thdng sd chdt lugng phii vi nhdn td thii 2 la thdi gian. So sinfa trung nud^ ttong 9 dgt thu mdu dugc trinh bay frong binh cdc nghiem thiic dya frln kiem dinh Tukey Bdng 2. Ty 11 che phu va thcri gian inh hudng din (5%) bdng phin mim Statgraphie Centurion XV tdt cd cdc tfafing sfi theo ddi. ngoai trir nhiet dd.
(StatPoinL Inc.. USA). .^^^^ ^^^^ ^^ ^^-j ^^ ^ ^ n^em thiic (NT) 3 KET QUA VA THAO LUAN che phu cd nhilt dp ttimg bmh 25.5-28,l°C va 3.1 Ch^t lugng nudc trong bl naoi ci theo ^d sy biin ddng nhilu theo tfadi gian (p<0.001;
thdi gian ^ ^ S 0 . nhung khdng cd sy kfaac bill giira cac be cd. Sy biln ddng nfaiet dp trong 1^ ca cd tfae do inh Qua kit qud thdng ke phuong sai 2 nhdn td cho faudng bdi diiu kiln thdi tiit ttong thdi gian 2 thiy cfi sy tucmg tic 2 nhin td ty ll che pfaii vd thcri thing thi nghiim. TTieo Duong Nhyt Long (2004), gian cho cdc chi tiiu theo doi pH vd TP. nhung ngudng nhilt dp do dugc nim trong khoing nhilt khdng cosy tuong ldc d cdc thfing sfi nhiet dp. DO, do pfaii hgp (24-30°C) cfao su pfadt triin cua ci EC va NH4-N (Bing 1). Tat ca cic thfing so DO, gac rgn
Bang 1: Kit qua thong ke phircmg sai 2 nfadn to (gia tri F) giua 2 nhan to ty-1| cfae phii va thdi giao eho chat lirgng nudc bl nuoi ca Sac ran
Tbdng sd Nhan tfi cfainh Ttrong tac
Ty le che phii Thdi gian T> le cfae phu x Tfadi gian
Nhietdd (X) 0,17-^ 35,65*" 0,42"*
pH 28,72"' 15,78'" 1.88' DO (mg/L) 6.27"' 50.65"' 1,55"
EC (pS/cm) 11.12"" 18.46'" 0,72""
NH4-N (mg/L) 3.07' 4.88"' 0,79^
TP (mg/L) 65.48"' 107.26'" 6,07'"
'P<0.05. "P<0.01. "'P<0.001: Khdc biet coy nghia o muc 5%. I%va0.1%
" Khong khdc biel CO y nghTa thdng ke
Bang 2: Gid tri trung binh cua cac chi tiiu ly, hoa nudc trong cac nghiem tfauc che phii TI.A.iBtii Tyle che phu
Nhijt do C O pH DO (mg/L) EC (MS/cm) NHj-N (mg/L) TP (mg/L)
0%
27,2 ± 0,2 7,4 ±0,2"
L8±0,6' 0,3 ± 0,02"
0,2 i O . ! ' 4.5 ± 0.6"
25%
27,2 ± 0,2 6,9 ± 0 , 1 ' 1,4 ±0,5'*
0.3 ± 0,02' 0,3 ±0.1"' 2,7 ± 0,5'
50%
27.2 ± 0,2 6.6 ±0,1 = 0,9 ± 0 , 5 ' 0 J ± 0.02"*
0 J ± 0 , 1 * 2.6 ± 0.7"
75%
27,2 ± 0,2 6,6 ±0,1' 0,8 ± 0.5' 0.18 ±0,02' 0,4 ±0,1"
2.4 ± 0,6' Ghi chu: Tmng binh = Do lech chudn. n=18 (9 dot thu mau x 2 ldn lap lgi)
* * ' ; khdc ky tu trong ciing 1 hdng Id khdc biet co y nghTa thong ke a muc y nghta 5% (dua tren hem dinh Tukey) Giafri pH trung binh Ciia cic bica dao dpng til thdp. Tfaeo Truong Qudc Phii & Vu Ngpc Ut 6.1-8,1 va cd sy khac bill theo thdi gian thu mau (2006). pH trong ninic cdng thdp flii xu hudng ty 11 {p<0.05). Gid fri pH bi anh hudng bdi ty 11 che NH4'/NH? cdng cao, dgc tinh it dfii vdi ddng vgt phu, d NT cd ty le che phu cang cao thi gid fri pH thiiy sinh. Hon niiaL cd Sdc rdn ti loii cd khi nang cang thap (p<0.001; Bing I). Dilu nay dugc gidi efaiu dung cac ap lyc ciia radi ttmmg cao. cd tfai thich do d cic bl ca che phii cao inh sdng khdng chiu dugc ngudng pH thip 4-4.5 (Duong Nhgt chilu xuong bi m^t nudc han chi sy phat friin ciia Long, 2004). nin gid tri pH do dugc ttong nghiin ldo. do dd qua frinh quang hgp hdp fliu CO2 kem cim nay Id phii hgp cho cd Sac rdn phdt niin. Diiu ddn din pH fliap hon (Dang Dinh Bach & Nguyin nij ciing phii hgp vdi nhdn dinh ciia Ngd Trpng Lu Viin Hdi. 2006) so vdi cdc bl cd cd ti te che phu
Tap chi Khoa hgc Tnr&ng Dgi hgc Cdn Tho Phan .i: Khoa hgc Tu nhien. Cong ngh? va Moi truang:: 120131 64-72 SL Thdi B i H d (2001), cfao r i n g pH 4,5-9,5 k h o i n g
thich hgp cho ci Sdc rin sinfa sdng.
Sau 8 tudn thu mdu, nhin cfaung nfing do oxy hda tan (DO) cd xu hudng gidm din vi cudi thi nghiim (p<0,O0T, Bang 1) vd cd sy kfadc bilt giiira cic be cd (p<0.01; Bdng 1). Ndng dfi DO trung binh frong cdc bi ci giam ddn theo sy ldng din ty te che phii, biin dfing tuang iing tir 0,8 din 1,8 mg/L (Bdng 2). CJ NT cd ty 11 che phu 0% (NT dfii chung khfing che phu) cd gia fri DO cao hon NT 50% vd NT 75%, cd thi do sy hien dien eiia beo Tai tugng da ngdn can su khuylch tin oxy tir khfing khi d NT cd t^* 11 che phu cao, bin cgnh beo ciing cdn oxy cho qua trinh fad hap. Mdt khdc, do sy che phu cua beo, tio d NT 50% vd NT 75%
ciing khfing phdt triln nhieu nin ndng dp DO frong nudc thdp hon. Vao nhiing dgt thu miu cudi, nfing dp DO ciia cdc NT hdu nhu gidm thip vi cd gid fri gdn bang 0 mg/L. Su tich luy chat hitu co thfing qua thiic an du thira, phdn cd, sy phdt ttiln va tin tyi ciia tao dan den tdng nhu ciu oxy cho sy phdn giii chat hiJu co va nhu cau oxy cho hoat ddng ciia ci ting theo thdi gian. Ngoii ra, diiu ki|n hi thdng nufii ca ciia nghiin cim nay la tuan hoin kin khdng thay nudc do dd din din vile giam ddn ham lugng DO frong nudc nudi vao cufii vy so vdi ban dau (Lin et al., 2002; Trang. 2009). Theo nh|n dinh ciia Ngfi Trpng Lu & Thai Ba Hfi (2001) thi nguong DO thdp nhat ma ca Sgc ran cd tfai sdng dugc li 1,4-2,3 mg/L. Nhy v^y, gid tri DO do vao thdi diem cudi vu (0,2-0,5 mg/L) trong nghiin ciiu ndy nhd hon ngyfing chiu dung cua cd Sic rdn. Duong Nhgt Long (2004) ghi nhan ring ci Sdc rdn cd co quan hfi hdp khi trdi, ci cd khd nang ddp khi kfai diiu kiln oxy hoa tan frong nudc thip. Qua quan sit thyc tien, ca Sac rdn trong bi nudi cd hoat ddng ddp khi vdo buoi sang d tit ca cdc nghi|m thitc.
Dilu ndy cd tfal anh huong din kfaa nang sinfa frufing ciia cd.
Gia tri EC frong nudc ciing giam dan khi ty 1?
che phu bi mat nudc tdng ip<0.001; Bdng 1 & 2) va biin ddng nhiiu giiia cdc dgt thu miu (p<0,001;
Bang 1 & 2). Kit qua nay ngugc lgi vdi nhgn djnh khi ndi vi vai tro ciia thyc vat thiiy sinh cy the la cung cdp oxy tao dilu kien cho cac vi sinh vat thyc hi^n cac qui trinh oxy hda, qua frinh nitrate hoa sinh ra nfaiiu ion hoa tan nhu NO2" va NOj" (Brix.
2003), ldm tdng EC trong nudc. Tuy nhien. d NT che phii cao nhdt (75%) mat dfi beo dugc thi vao be cao nhat, tfing sinh khdi la cao nhdt, do dd vai ttd cua beo dugc phit huy nhilu qua co chi hdp thu dinh dudng hda tan nhu PO^^" va NOj' tgo sinh
khdi lam giim nfing dfi cac chat hda tan nay, dan den sy gidm di cua gia fri EC frong nuoc (Bdng 2).
Theo Truong Qufic Phu & Vu Ngpc Ut (2006), NH4' frong nudc rdt can thilt cho sy phdt frien ciia cdc thyc vgt thiiy sinh, nhung nlu ham lugng NH4"
qud cao frong thiiy vyc gdy phii dudng, din din hien tugng tio nd hoa, khfing co lgi cho ci (vl thieu oxy cue bd vdo sang som, pH dao dpng trong ngiy nhilu...). Nfing dp NH4-N ed xu hudng tdng din theo sy tdng lln ciia ty 11 che phii (p<0,05;
Bing 2). Tai NT che phu 75% co ndng dp NH4-N cao hon NT 0% va khdng khic bilt so vdi 2 NT con lai (Bing 2). Dieu nay cho thiy ty 1? che phii anh hudng din nfing dfi NH4-N ttong bl nufii cd vi cd xu hudng ngugc lgi vdi kit qud ndng do DO ttong nudc (Bang 2), DO cang cao tao dilu ki|n cfao qui trinh nitrate hfia (Trang, 2009) lam cho ndng dp NH4-N gidm di d nghiim thiic 0% che phii. Tuy vay, beo van ddng tdt vai tro hdp thu dam ttong nudc ao nufii thfing qua chl tiiu dgm tfing ttong nghiim thiic che phu 75% li thap nhat (sfi lieu chtra cdng bfi). Nfing dfi NH4-N qua cde dgt thu mdu dao dfing trong khoang 0,06-0,86 rag/L (Hinh 2), vi co sy biln dfing theo thdi gian (p<0,00T, Bing 1). Sau 7 ngay ttien khai ngfailn ciru, nfing dp NH4-N giam d tit ca cac NT, sau dd tdng ttd lai d 2 tuan tiip theo. Cufii ciing, nfing dp NH4-N gidm vi duy fri d ndng dp thip cho din khi kit thiic tfai nghiim, so vdi ndng dp NH4-N ngiy ddu tiln thi khfing cd sy tich liiy NH4-N frong nudc cic be nudi ci (Hinh 2). Sy biin ddng NH4-N theo thdi gian cd thi lien quan din vile hip thu dinh duong ciia thuc vat va tio. Do sau I ludn bd tti, beo Tai tuong va tdo phat ttiln can dinh duong dl phat ttiin dan den nfing dp NH4-N ddng loat gidm.
Trong cac dpt thu mau cufii ciia thi nghi|m, beo Tai tupng di thich nghi vdi mfii ttuong nudc nudi cd vi sy hiln dien ciia tdo da giiip duy tri nong dp NH4-N ttong nudc.
Tdm lai, nfing dp NH4-N ttong nudc bi nufii cd phy tfaupe vao ty 1| che phu (Bdng 2), va cd gid tri ttung binh klidng cao (0,2-0,4 mg/L). Theo Boyd (1998), nfing dp NH4-N thich hgp ttong ao nufii thiiy sdn nhiet ddi dao dfing trong kfaodng 0,2- 2 mg/L, do do, nong dp NH4-N trong nghien cim hien tgi khfing la yeu tfi hgn chl sinh trudng ciia cd Sdc rin. Masser et al. (1999) khing dinh rdng nfing dp NH4-N cd mfii quan he mat thiit vdi NHs. la mpl dgng doc tfi ciia dfing vat thiiy sinh. Nfing do NH?
frong nudc dugc udc tinh dya vdo ndng dfi NH4-N, gia tri nhiet dp vd pH tgi thdi diem thu mau cufii cimg d 4 NT lin lugt li 0,003; 0,001; 0,002 vd
Tap chi Kboa hgc Truang Dgi hgc Cdn Tha PhdnA: Khoahgc Tunhien. Congnghf vd .Mdi truang- 2812013): 64-72 0,001 mg/L, tucmg iing d ty l l 0; 2 5 : 50 va 7 5 % .
Theo Masser el al (1999). ndng dp NH3 ttong khoang 0,02-0.07 mg/L lam cho ci chdm phdt triln vi nguy co gdy benh d mfit sfi loal ci nhilt ddi.
Nhu vdy. nfing dp NH3 frong nghien ciiu nay li rdt thdp, do do NH3 ciing kfafing infa faudng den sy smfa truong ciia ci Sic rdn.
Nfing dp TP cd xu hudng gidm din kfai ty 11 che phu ting lln vi cd sy biln dgng giiia cic dgt thu mau (p<0,OOT, Bdng 1 & Bang 2). Do nudc frong bl cd khfing dugc thay mdi, nin ndng dp lin frong bl ci sl tdng ddn theo qua trinh licfa liiy thirc an thira va bii tilt chdt thai ciia ca (Trang, 2009). Tuy nhien. frong nghiin cuu hiln tgi, d cac NT 25%, 50% vd 75% ndng dp TP cd xu huong giam vi
kfafing cd sy tich luy vao cudi vu nudi (Hinh 3).
frong khi chi ed sy tich luy TP d cdc bi ca ddi chiing khdng thd beo. Qua dd cho thiy, beo Tai tugng cd vai frd gdp phin giim thilu sy tt'ch liiy lin ttong nudc nudi cd theo thdi gian. hgn chi inh hudng xiu din sy sinh truong ciia cd Sdc rdn.
Thdng tfaudng lan trong ao nudi kfadng li yiu tfi gdy dfic cho cd, nhung ndng dp ldn cao giy ra hien tugng tio nd hoa frong nufifc ao nudi sl giy dpe giin tilp den vdt nudi vi thilu OTiy frong nudc va cic sin phdm ciia qud frinh phan fauy hilm khi.
Nlu khdng cd biln pfaip xir ly giim ndng dO lin frong nudfc thdi ao nufii thi khi thai ra mdi tnrdng kinh racfa. cd thi anh huong din chit lugng mfii tnrdng tfaiiy vuc (Konnerup et ai, 2011).
Hinh 2: Nong dp NH4-N trong nudc bi ^ cd ciia NT che pfaii 0% (•), 25% (o), 5
50% ( • ) va 75% (A) theo thdi gian ^
Tom lgi, sy co mil ciia beo Tai tugng gop phan ding ke vao vile giam thieu him lugng lan tdng qua CO chl hdp tfau dinh duong tao sinh khoi, cung cap oxy va re cung cdp gia bim cho cac loai vi sinh vdt phdn hiiy chat thii.
3.2 Sir sinfa trudng ciia beo Tai tugng Thyc vit ddng vai frd quan frgng trong he
thdng dit nggp nudc, chiing ting kha ndng loai bo chit dinh duong trong nudc thai thdng qua ca che hip thu dl tang sinh khdi. giiip van chuyin oxy xudng bfi re 3s cay sinh tnrdng vd phdt triin dugc frong dieu kien yIm kfai (bao hoa nudc), va lam gii bdm cho vi sinh vdt phat ttiin (Brix. 1994).
Hioh 3: Nong dp TP trong nirdc bl ca cna - NT che phti 0% (•), 25% (o), 50% ( • ) va J
75% (A) theo thdi gian ^
Tgp chi Khoa hgc Tru&ng Dgi hgc Cdn Tha Plidn A: Khoa hgc Tu nhien. Cong ngh? vd .Moi tnr&ng: 28 (2013). 64-' Theo quan sat ttong qud ttinh ngfailn ciiu ghi
nhdn dugc beo Tai tugng phat triin rdt tfit kfai kit hgp frong bl nufii cd Sac rin frong diiu kiln thi nghiim khfing thay nudc. Ben cgnfa vile gia tang sd tupng, sinh khfii than vi rl cung gia tang rat nhanh. La beo xanh tot, re ddi hon so vdi cic lai
Bang 3: Mpt si chi tieu sinh hpc cua beo Tai tugng d 3 ty II che phu 25,50 va 75%
beo frong mfii frudng tu nfailn. Sau 3 tudn friln khai tfai nghiim, beo Tai tugng da phat friin vd che phii todn bd dien tich cua be. Do dd, cdc tai beo da dugc thu hoach mpt phin nham tao dieu kiln cho cac tai beo cdn lai tdng truong vd phdt ttiin.
Chi tiiu
Sinh kh6i kho ban dSu (g/m-) Sinh khoi kh6 sau cung (g/m^) So ca the sau ciing (cay/be) SQRkh6(%/nsay)
2 5 % 1,4 500±0,1 396±6' 9,63±0.3
Nghi£m thiJc 5 0 % 1,4 400±0,1 332±3' 9,47±0,3
7 5 % 1,4 30a±0,04 325±13' 9,14±0,2
Oia tri P 0,15 0,02 0,07 Ghi chu: Trung binh ± Do lech chudn (n=2)
**; khdc ky lu trong cung 1 hdng Id khdc biet co y nghia thong ke a muc y nghta 5%
Tir ket qud ghi nhgn vl tfic dp lang truong sinh khdi tdifi >9 %/ngay d ca 3 ty 11 che phii (Bing 3), cho thdy beo Tai tugng tdng sinh khdi rdt nhanh frong ngfailn ciiu hien tai phii hgp voi ghi nhan cua Reddy & Busk (1984). VI beo Tai ttrgng cd sinh khfii ldn va cd gia fri dinh dudng cao nen dupe dimg lam ngudn cicbon bfi sung cho vi|c sin xuit khi mltan vi cdn lim thirc dn bfi sung frong chan nufii (Henry-Silva & Camargo, 2005), hodc san xuit phan xanh (Raju & Gangwar, 2004). Nghiin ciru ciia Biii Huy Thfing (2012) da cho thdy kha ning sir dung beo Tai tugng dl lim nguyen lieu ngp cho ttii li biogas khi thilu ngufin phan heo.
Ngoai ra, beo Tai tugng con cd kha ndng hip thu va giam chdt d nhiem trong nudc thai d^t may (Roy era/., 2010).
3.3 Sur tdng truong cua cd Sac rdo Trpng lugng trung binh ciia cd tha ban diu la 3,4-3,6 g/con. Sau 8 tuin nghien ciiu trpng lugng
ca dat tir 20,9-22,7 g/con, va cd xu huong li ci frong nghiim thuc khdng che phil co frpng lugng liic thu hoach cao faon. Tuy nhiin, cd frong nghiem thirc nay tai cfi tfic dp tdng frudng thip hon so vdi cic nghiim thiic con lgi (Bing 4). Ddn din trpng lugng ca tdng thim frong nghiem thiic khdng che phu (NT 0%) la thip (Bang 4). Kit qui thing kl cho thiy khfing cd sy khde bill ve frpng lugng cd liic thu hoach vd ttpng lugng ci tdng thim giira cic nghiem thiic (Bang 4).
Hieu qua thiic an cho ca an (%) trong nghiem thiic kfafing che phii (NT 0%) thap nhit so vdi cdc nghiim tfairc che phii cdn lai (p<0,05; Bdng 4).
Dieu cin quan tdm la ty 11 ca chit cao hon d nghiim thiir khdng che phii va sd lugng cd chit cfi xu huong giim din khi ty le che phii tSng (Bang 4).
Qua dd, cho thdy rdng khi cfi sy hiln diln ciia beo Tai tugng giiip cii thi|n dilu kien mfii trudng nudc ao nudi giiip cd thich nghi hon vi ting ty 11 sfing sdt cho ca.
Bang 4: IVIdt so chi tieu sinh hpc ciia cd Sgc rin d 4 t> le che phii 0,25, 50 vd 75%
Thdng so Nghiem thirc
0%
100,3=1,3 3,6±0,04 9,5=0,1 568=6,9 399±19 299±20 ) 5,0=0,4
54i4,r 1,5±0,02 2.3=0.1 84±5
25%
98,2±4,7 3,5±0,1 9,3±0,05 555±2,9 494±15 396±20 6,8±0,7 66,6±I,4-' 1,5±0,1 2,7±0,1 96±4
50%
95,8±2,7 3,4 ±0,1 9,7±0,4 581±25,8 495±3 399±6 7,0±0,3 7I,6±1,2' 1,4±0,05 2,7±0,05 98±2
75%
100,8±2,8 3,6±0,1 9,8±0,4 586±24,2 455±38 354±41 5,9±0,8 60,5±3,7-' 1,7±0,1 2,5±0,2 100±0
triF 0,55"
0,56"
0,39"
0,39"
3,94"
3,74"
2,38"
6,86' 5,78"
2,07"
5,06"
Trpng lupng ci ban dau (g/bl) Trpng lugng ca TB ban dau (g/con) Lugng thiic an TB (g/bi/ngay) Tfing lupng thuc Sn tuai (g/bi) Tfing trpng lugng ca cufii cung_(g/bi) Trpng lupng ca ting thira (g/bl)
Toe dp tang trudng trung binh theo ngay (%/ngay) Hi|u qua thiic in cho an (%)
HI sfi sii dyng thirc an SGR (%/ngay) Tv le sfing (%)
Ghi chu. Tnmg binh ^ Do lich chudn (n=2)
^'' khdc ki' tu trong ciing 1 hdng Id khdc Nil co y nghia ihdng ke a muc y nghia 5% (dua trin kiem dinh Tukey)
*p<0.05: khdc bi?! coy nghTa a mirc 5% "': Khong khdc biel
I lip chi Kboa boc Tnrang Dpi hgc Cdn Tha Phon .4 - Kboa hgc T\r nhiin, Cong nghe va Mdi truang. 28 (2013): 64- 72 4 KET LUAN VA D £ XUAT
4.1 Ket ludn
Beo Tai tugng ting truong vi phat friln tfit frong diiu kiln ket hop nufii ca Sac rin thim canh md khdng cin cung cip tfalm chdt dinh dudng vd CO khac.
Ty le che phii kfadng dnh faudng ten tfic dp ting tnrdng va sinh khfii ciia beo Tai tugng vi lit cd nhung thdng sfi sinh hpc ciia ed Sic rdn, ngoai trir hieu qua sii dyng thiic an.
- Ty 11 che phii inh faudng tin cfadt lugng nudc nufii ca cu thi li ty 11 che phu cdng cao nfing dp TP frong nudc cang giam, nhimg NH4-N cd xu hudng ngugc lgi.
He thfing nufii kit hop khdng thay nudc gfip phan gia ting hieu qua sir dung nudc va tan dyng dinh duong. gdp phdn ban che d nhilm mdi trudng nudc.
4.2 De xuat
- Nghilu ciiu ling dung ty le che phu beo Tai tuong tten ao nuoi cd Sac ran tham canh ngodi thuc tien.
Nghien cim thim cic md fainh kit hop be noi thyc vgt vdi cac loai thyc vdt thiiy sinh khae d cac ty le che phii frln ao nudi ca Sic ran thim canh.
LCn CAM T ^
Dy in niy dugc hd frg kinh phi tir dy in PhysCAM, Chinh phu Dan Mgch tii frg. Tac gia chin thanh cam on Bfi mdn Khoa hpc Mdi truong da nhiet tinh hfi ttg phong thi ngfailm. giiip chiing tfii hoan thanfa tfit kit qua nghien cuu nay.
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(APHA), American Water Works Association (AWWA), Water Conttol Federation (WCF), 1998. Standard mefliods for the examination of water and wastewater, 20th ed. Washington D.C., USA.
2. Boyd, C.E.. 1998. Water Qualit>' forpond Aquaculture. Reasearch and Development series No. 43. August 1998, Alabama. 37 pp.
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Aquatic Macrophyles for Wastewater Treatment in Constructed Wetland"'. Hosted by ICN and INAG, Portugal: 81-102 5. BuiHuyThdng,20t2.Kfainangsinhkhi
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Wang, 2002. Nuttient removal from aquaculture wastewater using a constructed weflands system. Aquaculture. 209: 169-184.
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Losordo. 1999. Recirculating Aquaculture Tank Production Systems, Management of Recirculating Systems. SRAC Publication No. 452.
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NXB Ndng nghiep Ha Ndi.
15. Raju, R. A. and B. Gangwar, 2004.
Utilization of potassium rich green leaf manures for rice {Oryza saliva) nursery and their effect on crop productivity. Indian Joumal of Agronomy. 49: 244-247.
Tap chi Khoa hoc Tnt&ng Dai hgc Cdn Tho PhdnA: Khoa hoc Tunhien, Cong nghe va Moi truang 28 (2013): 64-72 16. Reddy, K. R. and W. F. D. Busk, 1984.
Growth characteristics of aquatic macrophytes cultured in nutrient enriched water. Economic Botany. 38:229-239.
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Bai giang Quan ly chit lirpng nudc. Khoa Thuy san. Dai hpc Cin Tho.
