911103biofloc(thai)

Tp ch Khoa hc Trng i hc Cn Th Phn B: Nng nghip, Thy sn v Cng ngh Sinh hc: 30 (2014): 53-63

53

NH HNG CA MN N S HNH THNH V PHT TRIN CA BIOFLOC TRONG AO BN PHN Nguyn Vn Ha1, ng Kim Thanh, Nguyn Th Ngc Anh, Nguyn Th Hng Vn, Trng Ch Linh2 v Phm Th Tuyt Ngn1 1 Khoa Thy sn, Trng i hc Cn Th 2 Hc vin Cao hc K19, Khoa Thy sn, Trng i hc Cn Th

Thng tin chung: Ngy nhn: 19/11/2013 Ngy chp nhn: 26/02/2014 Title: The formation and development of biofloc in fertilized ponds at different salinities

T kha: biofloc, mn, ao bn phn, t l C:N, thnh phn sinh ha Keywords: Biofloc, salinity, fertilized pond, C:N ratio, proximate composition

ABSTRACT This study aimed to determine the suitable salinity for the development and formation of biofloc in fertilized ponds. The experiment was conducted at four different salinities (35, 60, 80 and 100 ppt) with 3 replicates per treatment and lasted for 21 days. Earthen ponds with area of 150 m2, water column of 30 cm were fertilized with chicken manure together tapioca to maintain the C:N ratio of 10. Results showed that the environmental factors (temperature, dissolved oxygen, pH) were suitable for the formation and development of biofloc. The C:N ratio ranges from 5 to 9. The TOC content at 35 ppt (20.21 to 50.5 mg/L) was less than at higher salinity (40 to 74.89 mg/L). The mean value of TSS and VSS were 20 to 670 mg/L and 7 to 126.6 mg/L, respectively and there was no significant difference among the treatments at day 18 and 21 (p>0.05). Total bacteria counts reached highest number at day 15 (4.1 log CFU/ml), the maximum volume of biofloc ranged from 0.4 to 0.5 ml and no significant difference among treatments (p>0.05). Vibrio, Bacillus, Nitrosomonas and Nitrobacter were found in all salinities, in which Bacillus presented with highest proportion. The ratio of un-known bacteria at salinity 60 ppt were very high (63-100%). At high salinity (80-100 ppt), floc size was smaller (32.5 - 61.5 m wide; 61.3 - 97.9 m long) than at low salinity (52,3 - 71.0 m wide; 76.7 - 105.3 m long). Proximate compositions analysis showed the low proportions of protein (8.5 to 17.4%) and lipid (0.65 to 1.08%), whereas ash content was very high (67.1 to 86.4%). TM TT Nghin cu ny nhm xc nh mn thch hp cho s pht trin v hnh thnh biofloc trong ao bn phn. Th nghim gm 4 nghim thc mn (35, 60, 80 v 100 ppt) v c lp li 3 ln, thi gian th nghim l 21 ngy. Ao th nghim c din tch 150 m2 vi mc nc 30 cm v s dng phn g + bt khoai m duy tr t l C:N 10. Kt qu th nghim cho thy cc ch tiu mi trng (nhit , oxy ha tan, pH) nm trong khong thch hp cho s hnh thnh v pht trin ca biofloc. T l C:N dao ng t 5-9. Hm lng TOC thp nht 35 ppt (20,21-50,5 mg/L) v cc mn cao t 40-74,89 mg/L. Hm lng TSS v VSS t 20-670 mg/L v 7-126,6 mg/L v khng c s khc bit gia cc mn ngy 18 v 21 (P>0,05). Mt vi khun tng t cao nht vo ngy 15 (4,1 log CFU/ml)), th tch biofloc cao nht l 0,4-0,5 ml v khng c s khc bit gia cc mn (P>0,05). C 4 nhm vi khun c pht hin l Vibrio, Baccillus, Nitrosomonas v Nitrobacter, trong nhm Bacillus lun chim t l cao tt c cc mn. T l vi khun cha nh danh mn 60 ppt chim rt cao (63-100%). mn cao (80-100 ppt) kch thuc ht biofloc nh hn (rng: 32,5-61,5 m v di: 61,3-97,9 m) so vi mn thp (rng: 52,3-71,0 m v di: 76,7-105,3 m). Phn tch thnh phn dinh dng ca biofloc cho thy t l ca protein (8,5-17,4%) v lipid (0,65-1,08%) u thp, trong khi , hm lng tro rt cao (67,1-86,4%).


54

1 GII THIU Biofloc (hay cn gi l bng cn sinh hc) l

hn hp gm nhiu loi vi sinh vt khc nhau gm mnh vn hu c, ht keo, cation v cc t bo cht, Trong nui trng thy sn, cng ngh biofloc c th c ng dng nh mt phng php qun l cht lng nc, da vo s pht trin v kim sot vi khun d dng trong h thng nui vi vic khng hoc t thay nc (Avnimelech 2007; De Schryver et al., 2008). Khi cng ng vi khun pht trin, biofloc c hnh thnh (Jorand et al., 1995; Hagreaves, 2006; Avnimelech, 2007; De Schryver et al., 2008), sau biofloc c th c ng vt nui tiu th nh l mt ngun thc n, to thnh mt qu trnh ti s dng cht dinh dng trong h thng nui trng thy sn. Cung cp t l C:N thch hp nhm thc y s pht trin ca vi khun d dng bng cch ng ha ammonia trc tip t mi trng nc sn xut protein cho t bo (Avnimelech, 1999; Crab et al., 2009). Trong iu kin t l C:N cao (10-20), vi khun d dng l thnh phn ch yu ca biofloc s ng vai tr trong x l nc v sn xut thc n t nhin, gim chi ph thc n v x l cht thi (Kent et al., 2011). Cng ngh BFT tr thnh mt cng ngh rt c a chung trong nui tm th chn trng. Cng ngh ny bc u thnh cng Belize (Chamberlain et al., 2001), Innxia (Taw, 2005), tm s c (Smith, 2008) v c r phi Israel (Avnimelech, 2007).

Nhn chung, cc nghin cu v biofloc tp trung trn mt s i tng l mn vi mn mi trng trong khong 30-35 nh tm th chn trng, tm s, c r phi, Trong khi thnh phn

ca biofloc gm vi khun, to, mn b hu c, c th l thc n cho mt s i tng n lc sng mn cao hn (80-100 ppt) nh Artemia, vn l i tng n lc khng chn la (Sorgeloos, 1986) cha c quan tm, do vic nghin cu s hnh thnh biofloc cc mn khc nhau l rt quan trng nhm tm ra mn thch hp ng dng cng ngh BFT cho ngh nui Artemia trn rung mui.

2 PHNG PHP NGHIN CU 2.1 Vt liu nghin cu Nghin cu c thc hin trong 3 tun t

ngy 06 n 27 thng 01 nm 2013 ti Tri Thc nghim Vnh Chu (i hc Cn th), Phng Vnh Phc, Th x Vnh Chu, tnh Sc Trng.

2.2 B tr th nghim Th nghim gm 4 nghim thc (NT) mn

vi 3 ln lp li: 35, 60, 80 v 100 ppt. Cc NT c b tr trong cc ao t c din

tch: 150 m2, mc nc 30 cm. Ao th nghim khng lt bt, khng c mng

quanh v khng lp h thng sc kh. Chm sc v qun l th nghim: nc c

cp vo cc ao th nghim 1 ln/2-3 ngy. Ba trc mi ngy hai ln vo sng sm v lc gia tra.

B sung phn g v bt m vo cc ao nhm duy tr t l C:N 10, tnh ton lng s dng da vo cch tnh Avnimelech (1999) vi liu lng:

Phn g: 1,5 kg/ao 150 m2 (100kg/ha/3ngy). Bt m: 0,3 kg/ao 150m2 (20 kg/ha/3ngy)

Bng 1: Hm lng P, C, N ca phn g v bt m (% khi lng kh) Nguyn liu m P C N C:N Bt khoai m 10,92 0,45 0,41 0,11 72,14 1,81 1,32 0,09 54,61 4,91 Phn g 23,72 2,04 4,25 2,27 14,83 2,06 1,88 0,57 8,23 2,05

2.3 Thu thp v phng php phn tch mu Nhit , pH, oxy ho tan o bng my mi

ngy vo lc 7:00 h v 14:00 h. Thu mu nc cc nghim thc tin hnh

phn tch tng carbon, tng cht rn l lng v cht rn l lng bay hi (phng php APPHA et al., 1995): 1 ln/3 ngy, mu c thu vo lc 7 h sng. Thu 5 im trong ao, sau trn u v ly mi ch tiu mt mu. Mu nc c tr mt 4oC.

Tng vi khun (trong mi trng nc), th tch biofloc: 1 ln/3 ngy

Gi tr dinh dng, kch thc biofloc: thu vo ngy 7, 14 v 21.

o kch thc ht biofloc: thu mu biofloc vo chai nha 100 mL v c nh bng formol vi nng t 2-4%, sau mu c o di knh hin vi c thc o.

2.4 Phng php x l s liu Php phn tch ANOVA - STATISTICA,

version 7.0 c s dng tm s sai bit c ngha thng k gia cc nghim thc mc p


55

gi tr trung bnh v lch chun ca cc s liu v v th v s bin thin ca chng.

3 KT QU Trong qu trnh th nghim cc yu t mi

trng nh nhit nc dao ng t 27,8oC n 30,7oC vo bui sng v 30,2-36,6 oC vo bui chiu; pH trung bnh gia cc nghim thc dao ng t 7,2-8,3. Hm lng oxy ha tan gia bui

sng (4,42-6,73 mg/L) chnh lch khng nhiu so vi bui chiu (5,58-10,92 mg/L).

T l C:N c khuynh hng gim dn khi mn tng, kt qu Hnh 1 cng cho thy NT 35 v 60 ppt, t l C:N gim mnh trong 3 ngy u trong khi cc NT c mn cao hn (80 v 100 ppt) th t l C:N tng i n nh v dao ng t 5-9.

Hnh 1: Bin ng hm lng C:N gia cc NT trong ao bn phn

Hm lng TN trung bnh cc nghim thc trong th ngim dao ng t 3,8-11,8 mg/L (Hnh 2). Hm lng TN khng c s bin ng ln v tng i n nh cc nghim thc qua cc t thu mu, tuy nhin c s chnh lch gia

cc NT v c xu hng tng khi mn tng. C th hm lng TN thp nht NT 35 ppt (3,8-4,2 mg/L) tng dn theo mn v t cao nht NT 100 ppt (8,7-11,8 mg/L).

Hnh 2: Bin ng hm lng TN gia cc NT trong ao bn phn

Tng carbon (TOC = Total Organic Carbon): Hm lng TOC c khuynh hng gim t ngy 0 n ngy 6 ca th nghim sau c khuynh hng tng dn v tng i n nh cho n cui th

nghim (Hnh 3). Hm lng TOC cc NT dao ng trong khong 20,21-74,89 mg/L, thp nht l NT 35 ppt v cao nht l 100 ppt.


56

Hnh 3: Bin ng hm lng TOC gia cc NT trong ao bn phn

nh gi cng ngh biofloc trong ao bn phn thng qua cc thng s TSS, VSS, tng vi khun v th tch biofloc cho thy:

Tng cht rn l lng (Total Suspended Solids-TSS): Hm lng TSS trong cc NT dao ng trong khong 20-672 mg/L. Nhn chung, TSS c khuynh hng gim dn sau 9 ngy th nghim sau

tng tr li v tng i n nh v cui th nghim. Kt qu thng k cho thy cc NT gn nh khng khc bit c ngha thng k ngoi tr NT 100 ppt (ngy 0) v NT 60 ppt (Ngy 15 v 18) khc bit c ngha so vi cc NT cn li (Bng 2).

Bng 2: Bin ng hm lng TSS v VSS gia cc NT trong ao bn phn (mg/L) Ngy TSS 35ppt 60ppt 80ppt 100ppt

0 256,766,0a 157,510,6 a 98,530,5 a 67238,3 b 3 60,00,0 a 20,05,7 a 207,538,9 ab 321,97,6 b 6 55,07,1 b 30,00,0 a 37,53,5 ab 47,53,5 ab 9 59,521,9 a 75,50,7 a 68,011,3 a 70,014,1 a

12 100,028,3 a 370,070,7 b 137,538,9 a 107,53,5 a 15 56,84,6 a 365,035,4b 205,07,1 a 51,01,4 a 18 162,53,5 a 170,056,6 a 170,042,4 a 108,54,9 a 21 80,028,3 a 135,07,1 a 145,021,2 a 82,53,5 a VSS 0 60,91,3 b 55,00,0 b 26,54,9 a 126,67,6 c 3 22,53,5 ab 8,00,0 a 57,510,6 c 39,56,4 ab 6 10,50,7 a 10,00,0 a 7,00,7 a 12,53,5 a 9 11,85,3 a 14,02,8 a 12,00,0 a 22,53,5 a

12 12,53,5 a 103,04,2 b 30,07,1 a 27,53,5 a 15 11,51,4 a 110,014,1 b 17,00,0 a 14,50,7 a 18 45,014,1 a 55,07,1 a 20,00,0 a 47,510,6 a 21 15,00,0 a 50,014,1 a 26,31,8 a 22,53,5 a

Cc gi tr trong cng mt hng c k t (a, b, c) khc nhau biu th s khc bit c ngha p


57

Hnh 4: Bin ng tng vi khun gia cc NT trong

ao bn phn

Khi phn tch thnh phn vi khun (Bng 3)

cc nghim thc cng cho thy c 4 nhm vi khun c pht hin l Vibrio, Baccillus, Nitrosomonas

v Nitrobacter, trong nhm Bacillus lun chim t l cao tt c cc NT.

Bng 3: Bin ng t l vi khun/ tng s vi khun/tng s vi khun theo thi gian Ngy 0 3 6 9 12 15 18 21

35 ppt Vibrio 0 0 0 0 0.12 0.08 0.19 2.23 Bacillus 2.05 5.07 3.82 2.45 23.50 42.91 12.42 6.13 Nitrosomonas 0.00 0.00 0.00 2.45 1.27 2.08 1.55 5.01 Nitrobacter 0.00 0.00 0.00 0.00 0.12 0.85 3.11 6.68 Khc 97.95 94.93 96.18 95.09 75.00 54.09 82.72 79.95

60 pptVibrio 0 0 0 0 0.00 0.11 1.45 1.77 Bacillus 1.86 1.67 3.11 0.41 3.56 7.12 4.50 11.98 Nitrosomonas 0.00 0.00 0.00 1.24 1.66 1.61 1.13 1.57 Nitrobacter 0.00 0.00 0.00 0.00 0.24 0.57 1.45 1.77 Khc 98.14 98.33 96.89 98.35 94.55 90.58 91.47 82.91

80 pptVibrio 0 0 0 0 0.00 0.00 0.72 1.43 Bacillus 6.00 4.92 1.31 1.21 2.67 3.19 1.99 15.36 Nitrosomonas 0.00 0.00 0.00 1.21 1.15 1.22 1.27 1.25 Nitrobacter 0.00 0.00 0.00 0.00 0.38 0.38 1.09 1.25 Khc 94.00 95.08 98.69 97.58 95.80 95.22 94.93 62.84

100 pptVibrio 0 0 0 0 0 0 0 0 Bacillus 0.00 0.00 0.00 0.00 1.78 0.77 13.35 21.24 Nitrosomonas 0.00 0.00 0.00 0.31 0.30 1.28 2.36 1.86 Nitrobacter 0.00 0.00 0.00 0.00 0.09 0.39 2.36 1.86 Khc 100.00 100.00 100.00 99.69 97.84 97.56 81.94 75.05

Kt qu cng ch ra rng t l vi khun Vibrio mn cao thp hn so vi mn thp, in hnh nh NT 100 ppt khng pht hin nhm Vibrio. Ngoi ra, Bng 3 cng cho thy t l vi khun khc mn 60 ppt chim rt cao (63-100%). y c th l cc dng vi khun a mn (Halophilic bacteria) cha c nh danh trong mu nghin cu.

Th tch ca biofloc (bng cn sinh hc) ca th nghim c trnh by Hnh 5.

Theo , th tch ca biofloc cc NT 60, 80, 100 ppt xut hin ngay t u v c khuynh hng tng dn v t mc cao t ngy 9-15 sau gim dn v cui th nghim. Th tch biofloc ti a l 0,4-0,5 ml/L v khng c khc bit ln gia cc NT (p>0,05).

Kch thc ca biofloc cng c o thi gian th nghim v c trnh by Bng 4.


58

Hnh 5: Bin ng th tch biofloc gia cc NT trong ao bn phn

Bng 4: Bin ng kch thc ht biofloc (x std, m) trong thi gian th nghim Nghim thc

Ngy 35 ppt 60 ppt 80 ppt 100 ppt Rng Di Rng Di Rng Di Rng Di 7 62,630,2 93,630,4 59,825,9 76,727,4 51,628,8 81,446,6 39,711,4 74,530,5

14 71,020,4 105,330,9 57,522,3 102,636,4 61,530,5 97,951,4 37,126,1 61,336,8 21 52,318,7 98,255,7 55,319,4 80,641,6 32,519,6 66,328,3 33,815,8 49,722,2 Kch thc ht biofloc trung bnh cc NT

bin ng trong khong 32,5-71,0 m i vi chiu rng v 49,7-105,3 m i vi chiu di. Trong cng mt nghim thc, bin ng kch thc ht biofloc tng i ln (LC ln). Theo thi gian nui, kch thc ht biofloc c xu hng tng vo ngy 14 (ngoi tr NT 100 ppt) sau gim dn vo ngy 21. Nhn chung, mn cao (80-100 ppt) kch thc ht biofloc dng nh nh

hn (32,5-61,5 m chiu rng v 61,3-97,9 m chiu di) so vi mn thp (52,3-71,0 m chiu rng v 76,7-105,3 m chiu di).

Khi phn tch gi tr dinh dng ca biofloc trong thi gian th nghim cho thy hm lng protein tng i thp dao ng t 8,5-17,4%, hm lng lipid 0,65-1,08%. Trong khi , hm lng tro li rt cao v dao ng t 67,1-86,4%.

Bng 5: gi tr dinh dng ca biofloc (% khi lng kh) trong thi gian th nghim Nghim

thc Thi gian thu mu

Ngy 7 Ngy 14 Ngy 21 Protein Lipid Tro Protein Lipid Tro Protein Lipid Tro

35 ppt 12,2 b 0,80 a 69,9 b 17,4 a 1,05 a 67,1 a 9,3 a 0,65b 86,4 a 60 ppt 10,5ab 0,89 a 76,2 ab 16,4 a 0,92 a 70,4 a 12,4 b 1,02 a 74,8 a 80 ppt 9,8 a 0,77 a 80,6 a 15,6 a 1,08 a 69,9 a 10,4 a 0,83 ab 81,0 a 100 ppt 8,5 a 0,67 a 82,2 a 15,9 a 0,94 a 71,7 a 9,6 a 0,91 a 78,9 a

Nhn chung, gi tr dinh dng ca biofloc cc nghim thc c s chnh lch. Hm lng protein cc NT 80 v 100 ppt thp hn 35 v 60 ppt, tuy nhin hm lng tro th ngc li (cao hn). Kt qu cng ch ra rng hm lng protein cc NT u t cc i vo ngy 14, sau gim ngy 21 (Bng 5).

4 THO LUN Wilen et al. (2000) thy rng s kt dnh ca

floc xy ra nhit thp (4C) km hn so vi

nhit cao (18-20C), c th l do s st gim hot ng ca vi sinh vt trong bioflocs. Krishna and Van Loosdrecht (1999) cho rng nhit nc trung bnh 20-25C l tt nht bioflocs n nh v nhit cao hn (30-35C) s dn n hin tng bn kh lng (SVI 500 ml/g) do s sn xut qu mc ca ng a phn t ngoi bo. Nhit 28-30oC c coi l khong ti u cho s pht trin ca biofloc (Nguyn Th Thu Hin, 2012). Nhit c theo di trong th nghim ny dao ng trong phm vi 27-36,6oC. Kt qu ny

0.000.100.200.300.400.500.60

0 3 6 9 12 15 18 21Thi gian th nghim (ngy)

Th t

ch bi

o-floc

(ml/L

)

35 ppt 60 ppt 80 ppt 100 ppt

a

a

aa a

abab

b

aaaa a

aaaaaaaa

a

aaa

aab

b

aaa

a


59

tng ng vi kt qu Trn Nguyn Hi Nam (2012) khi theo di kh nng pht trin ca vi khun d dng bng cch b sung ngun carbohydrate t bt khoai m cng cho thy phm vi nhit trong khong 24-36oC. Boyd (1998) cho rng nh hng ca nhit rt phc tp, nhit khng ch nh hng trc tip ln qu trnh trao i cht ca vi sinh vt m cn tc ng n hm lng oxy ha tan trong nc.

Hm lng oxy ha tan khng ch nh hng n hot ng trao i cht ca cc t bo trong ht biofloc hiu kh m cn tc ng n cu trc biofloc (Wilen and Balmer, 1999). Kch thc v n nh ca cc ht biofloc c xu hng c ci thin khi hm lng oxy ha tan tng (De Schryver et al., 2008). Mt s nghin cu trong cc h thng nui vi cng ngh biofloc cho thy hm lng oxy ha tan thch hp cho i tng nui v s pht trin ca biofloc thng >3 mg/L (Nyan Taw, 2005; Trn Nguyn Hi Nam, 2011, Widanarni et al., 2012, Emerenciano et al., 2012). Do hm lng oxy ha tan trong th nghim cu ph hp vi cc nghin cu trn v khng nh hng n qu trnh hnh thnh biofloc.

pH l mt trong nhng yu t mi trng c s lin quan ln nht ti s tng trng ca vi sinh vt. Vi sinh vt chim u th trong phm vi pH c li cho dinh dng, sinh sn v tn ti Carvalho, 1978). Do , thay i pH c th nh hng n tnh n nh ca biofloc trong ao nui (Mikkelsen et al., 1996). Nguyn Th Thu Hin (2011) cho rng khi pH < 7,1 th ch s FVI (Floc Volume Index) ca biofloc 7,3. Trong mt th nghim tng t gn y ca Trn Nguyn Hi Nam (2012) cng cho thy pH dao ng trong trong khong 7,1-8,4 tng t nh kt qu trong th nghim ny (7,2-8,3). Madigen et al. (2000) cho rng cc loi nm pht trin tt trong iu kin c tnh axit, trong khi vi khun pht trin trong mi trng kim, mt khc phm vi pH thch hp cho s pht trin ca hu ht cc loi to (l thnh phn ca biofloc) l 7-9, ti u l 8,2-8,7 (Richmond, 1986). Nhn chung, cc yu t mi trng c s chnh lch gia cc NT nhng vn nm trong khong thch hp cho s pht trin ca biofloc.

Protein l thnh phn ch yu to nn t bo vi khun. T l C:N hu ht vi khun l t 4-5 (Ebeling and Timmons, 2006). Khi vi khun c cung cp c cht cha carbon khng c hoc c rt t nitrogen (nh cc loi ng, bt, r ng

protein, bt khoai m,) chng phi ly nitrogen t mi trng nc sn sinh ra protein cn thit cho s pht trin v nhn ln ca t bo. Nhiu tc gi (Avnimelech 2007; Samocha et al., 2007; De Schryver et al., 2008; Crab et al., 2007; Hargreaves, 2013) cho rng t l C:N thch hp, vi khun d dng c nh nit v c trong mi trng chuyn ho thnh sinh khi ca chng, lng sinh khi vi khun ny cc iu kin nht nh s gn kt thnh phn khc to thnh biofloc. Jana et al. (2001) cho rng t l C:N trong khong 5-55 gip cho s pht trin ca h vi khun d dng. Khi nghin cu h sinh thi nc l ven bin, Lancelot and Billen (1985) kt lun vic hp th nit v c ca vi khun ch din ra khi t l C:N ca vt cht hu c >10. V nh vy vic gia tng t l C:N c th lm tng ln sc sn xut ca vi khun trong ao nui tm (Burford et al., 2003). T l C:N 8 10 vi khun t dng chim 64,4% v 35,6% l vi khun d dng. Khi t l C:N 12 14 gn nh vi khun d dng chim 100% (Ebeling and Timmons, 2006). T l C:N cao hn 15 c xem l hiu qu kim sot s tch t ca cc hp cht nitrogen cng nh qu trnh ti to protein. Mt s tc gi (v d Tezuka, 1990; Avnimelech, 1999; McIntosh, 2000; Panjaitan, 2010, Widanarni et al., 2012) bo co rng t l C:N tng ng l 15:1 c xem l hiu qu loi b ni t t nc. Trong th nghim ny vic b sung phn g v bt khoai m duy tr t l C:N10, mc d vy kt qu t Hnh 1 cho thy t l C:N cc NT trong thi gian th nghim ch bin ng trong khong 5,2-9


60

nitrogen thm vo c chuyn sang dng nitrogen hu c l lng (nitrogen trong biofloc).

Theo Rittman and McCarty (2001) th lng biofloc c th c c tnh da trn hm lng TSS v VSS. Hm lng VSS c s dng nh thc o sinh khi ca vi khun (Rittmann and McCarty, 2001; Ebeling et al., 2006). Kt qu thng k Bng 2 cho thy hm lng TSS v VSS trong th nghim khng c s khc bit ln gia cc NT, mn 80 v 100 ppt cho thy khng c khc bit thng k (p>0,05) vi 35 v 60 ppt, iu ny ch ra rng mn trong phm vi nghin cu khng nh hng n thng s TSS v VSS. Bn cnh , Kuhn et al. (2008) cho rng b sung ngun carbon lm gia tng tc hnh thnh ca biofloc (vi khun d dng l thnh phn vi sinh chnh trong biofloc). S pht trin ca vi khun d dng cng c th c nh gi thng qua biofloc. Tng t nh TSS v VSS, tng vi khun (Hnh 4) v th tch biofloc (Hnh 5) cng cho thy khng c khc bit ln gia cc NT v thp hn cc nghin cu ca Nguyn Th Thu Hin (2011) v Trn Nguyn Hi Nam (2012). Nguyn nhn c th do thi gian th nghim qu ngn (21 ngy) trong khi cc nghin cu khc l trn 30 ngy, t l C:N trong th nghim ch dao ng trong khong 5-90,05). Thnh phn chnh ca biofloc l vi khun v to. Trong th nghim, ngoi cc chng vi khun c xc nh nh Vibrio, Bacillus, Nitrosomonas v Nitrobacter th cn cc chng vi khun khc (Bng 3) chim t l rt cao trong cc nghim thc. C th y l nhng vi khun a mn. Deng et al. (2013), nghin cu thnh phn vi khun a mn (Hallophilic bacteria) trn rung mui Trung Quc cho thy phn ln vi khun hot ng nng mui t 0-250 ppt, nng mui ti u l 50 ppt. Phm vi mn trong th nghim cng nm trong khong hot ng ca vi khun. Mt khc, mt s nghin cu cho thy mn khng c nh hng trc tip n s tng trng ca vi khun, mn tng ln hoc h xung s chn lc cc loi c chc nng sinh l mi c kh nng chu ng cc nng mui nht

nh (Del Giorgio and Cole, 1998;. Nielsen et al., 2003).

De Schryver et al. (2008) cho rng vi khun c kch thc rt nh (khong 1 m). Tuy nhin, mt cao, vi khun c khuynh hng kt dnh vi nhau v to thnh ht biofloc c ng knh khong 0,1 mm n vi mm. Kch thc ca ht biofloc trng thi n nh trong cc h thng biofloc l mt ch tiu quan trng v trong nui trng thy sn, kch thc ca ht thc n cng l mt trong nhng tiu ch th hin cht lng thc n (De Schryver et al., 2008). Do vy, qui trnh vn hnh cng ngh biofloc c th c iu chnh cn i kch thc ca ht biofloc theo yu cu ca i tng nui tng giai on sinh trng khc nhau. Nu cng khuy o v lu tc dng chy cao, kch thc trung bnh ca ht biofloc s gim do chng b v ra (De Schryver et al., 2008). Biggs and Lant (2000) cho bit khi s dng bn hot tnh x l nc, vi bin thin lu tc trung bnh (G) l 19,4/s (0,5 W/m3) th kch thc trung bnh ca t bo l 130 m. Kch thc t bo gim xung ch cn khong 20 m khi bin thin lu tc tng ln n 346/s (125 W/m3). Trong th nghim ny, ba trc 2 ln/ngy l phng php c s dng nhm khuy o dng nc tc ng lm v ht biofloc v lm chng c kch thc nh hn ph hp cho i tng nui. Mt khc, kt qu trong th nghim cho thy mn cao 80 v 100 ppt kch thc ht biofloc nh hn mn thp (35 v 60 ppt) (Bng 4 v Hnh 6). De Schryver et al. (2008) cho rng c nhiu c ch kt hp nh hng n s hnh thnh, hnh dng v s bn vng ca biofloc. Nhiu sinh vt c kh nng to cc hp cht cao phn t ngoi bo (t cc polysaccharide, protein, hp cht mn). Cc hp cht ny c xem nh cht keo gn kt t bo v cc phn t khc li vi nhau. Ngoi ra cn mt c ch kt dnh khc l s cn bng gia lc ht khong cch ngn (tng tc phn t, lng cc, lin kt hydrogen) v lc y tnh in. Hin nay vn rt t ti liu nghin cu v kh nng kt dnh ht biofloc mn khc nhau mc d hu ht sinh vt mang in tch m v to ra lc y tnh in, khi mn cao (lc ion cao) hoc ion a ha tr chim u th, vic b sung Ca2+ hoc Al3+ to nn s kt dnh bn vng (De Schryver et al., 2008). Do c th khi mn cao th s kt dnh km bn, d b ph v nn kch thc ht biofloc mn cao nh hn. Ngoi ra, mn cao vi khun pht trin chm hn mn thp (cng thi im) dn n kch thc cng khc nhau.


61

Hnh 6: Hnh dng v kch thc ca biofloc mn 100 ppt (a)) v 60 ppt (b)) ngy 21 Kt qu phn tch dinh dng ca biofloc cho

thy khng c s khc bit ln cc mn khc nhau. Hm lng protein trong ht biofloc cc NT rt thp (8,5-17,4% khi lng kh), trong khi cc nghin cu trc y (McIntosh et al., 2000; Tacon et al., 2002; Soares, 2004; Wasielesky et al., 2006; Ju et al., 2008, Kuhn et al., 2009; Maica et al., 2011; Emerenciano et al., 2012) th hm lng protein kh cao (12-49% khi lng kh). Ngc li, hm lng tro trong th nghim li rt cao chim 67,1-86,4% so vi cc kt qu khc l 13-46%. McIntosh (2000) v Tacon (2002) u xc nh hm lng tro ca ht biofloc mc cao nhng trung bnh cng ch t 26,0 v 30,2%. Thnh phn dinh dng ca biofloc khc bit ty thuc vo iu kin mi trng, ngun carbon s dng, hm lng TSS, mn, mt nui, cng chiu sng, qun x thc vt ph du v vi khun(Kuhn and Lawrence, 2012). De Schryver et al. (2008) cng cho rng thnh phn dinh dng ca biofloc c s khc bit ng k khi ngun carbon b sung khc nhau. Vic b sung cc ngun carbon khc nhau (nh glucose, tinh bt, glycerol hoc acetate) to ra nhng khc bit ng k v hm lng ca cc nhm acid bo (Crab et al., 2010). Ngoi ra, trong biofloc cn c to, nm v mt lng ng k cc sinh vt s dng chng lm thc n nh ng vt nguyn sinh hoc ng vt ph du. S hin din ca nhng tc nhn ny c th nh hng n t l phn trm ca hm lng dinh dng trong biofloc. Nhn chung, nh hng ca mn ln s hnh thnh v pht trin ca biofloc trong th nghim ny vn cha r rng. Mc d Timmons et al. (2002) lu rng pH, kim, nhit , oxy, amoniac, v mn cng nh hng

n s pht trin ca vi khun d dng, tuy nhin cc ti liu nghin cu c lin quan rt hn ch c th so snh c th trong th nghim ny.

5 KT LUN V XUT 5.1 Kt Lun T l C:N gim nhanh mn 35 v 60

ppt trong 3 ngy u, cc mn cao hn th t l C:N n nh trong mc t 5-9; sau 2 tun t l C:N gim khi mn tng ln.

Cc thng s nh gi cht lng biofloc TSS, VSS, tng vi khun v th tch biofloc cho thy: hm lng TSS v VSS tng dn theo thi gian nui. Tng t, tng vi khun cng tng dn v t cao nht vo ngy 15. Th tch biofloc gim dn theo mn.

Vi khun vibrio chim t l rt thp v mn cao (100 ppt) khng pht hin nhm vi khun ny.

T l vi khun khc cha c nh danh mn 60 ppt chim rt cao.

Kch thc ht biofloc cc mn 35 v 60 ppt ln hn mn 80 v 100 ppt.

Hm lng protein tng i thp ( mn cao hm lng protein thp hn). Trong khi , hm lng tro li rt cao.

5.2 xut Ko di thi gian th nghim v gia tng t

l C:N vi khun d dng pht trin tt hn. C th ng dng cng ngh biofloc cho i

tng nui Artemia mn thch hp da vo kch thc ht floc (80-100 ppt).

2,6 m a) b)


62

TI LIU THAM KHO 1. Avnimelech, Y. 1999. Carbon/nitrogen ratio

as a control element in aquaculture systems. Aquaculture 176:227-235.

2. Avnimelech, Y. 2006. Bio-filters: the need for an new comprehensive approach. Aquac. Eng. 34 (3), 172178.

3. Avnimelech, Y. 2007. Feeding with microbial flocs by tilapia in minimal discharge bioflocs technology ponds. Aquaculture 264, 140-147.

4. Boyd, C.E., 1998. Pond water aeration systems. Aquac. Eng. 18 (1), 940.

5. Burford, M. A., Thompson, P.J., McIntosh R. P., Bauman R. H., Pearson D. C. 2003. Nutrient and microbial dynamics in high-intensity, zero-exchange shrimp ponds in Belize. Aquaculture 219: 393411.

6. Crab, R., Avnimelech, Y., Defoirdt, T., Bossier, P., Verstraete, W. 2007. Nitrogen removal in aquaculture towards sustainable production. Aquaculture 270 (14), 114.

7. Crab, R., Kochva, M., Verstraete, W., Avnimelech, Y. 2009. Bioflocs technology application in over-wintering of tilapia. Aquac Eng 40:105-112.

8. Chamberlain, G., Avnimelech, Y., McIntosh, R.P., Velaso M. 2001. advantages of aerated microbial reuse systems with balanced C:N. I. Nutrient transformation and water quality benefits. Global aquaculture advocate 4: 53-6

9. De Schryver, P. 2010. Poly--hydroxybutyrate as a microbial agent in aquaculture. PhD thesis, Ghent University, Belgium.

10. De Schryver, P., Crab, R., Defroit, T., Boon, N. and Verstraete, W. 2008. The basic of bioflocs technology: The added value for aquaculture. Aquaculture 277, 125-137.

11. Del Giorgio, P., Cole, J.J. 1998. Bacterial growth efficiency in natural aquatic systems. Annu Rev Ecol Sys 29:503-541.

12. Ebeling, J.M., Timmons, M.B., Bisogni, J.J. 2006. Engineering analysis of the stoichiometry of photoautotrophic, autotrophic, and heterotrophic removal of ammonianitrogen in aquaculture systems. Aquaculture 257: 346358

13. Emerenciano, M., Ballester, E.L.C, Cavalli, R. and Wasielesky, W. 2012. Biofloc

technology application as a food source in a limited water exchange nursery system for pink shrimp Farfantepenaeus brasiliensis (Latreille, 1817). Aquaculture Research 43: 447457.

14. Hargreaves, J.A. 2013. Biofloc Production Systems for Aquaculture. 11p.

15. Hargreaves, JA. 2006. Photosynthetic suspended-growth systems in aquaculture. Aquac Eng 34:344-363.

16. Jana, B. B., Chakraborty, P., Biswas, J. K., Ganguly, S. 2001. Biogeochemical cycling bacteria as indices of pond fertilization: importance of C:N/P ratios of input fertilizers. Journal of Applied Microbiology 90: 733-740.

17. Jorand, F, Zartaria, F, Thomas, F, Block J.C, Bottero, J.Y, Villemin G, Urbain V, Manem J. 1995. Chemical and structural (2d) linkage between bacteria within activated-sludge flocs. Water Res 29:1639-1647.

18. Ju, Z.Y., Forster, I., Conquest, L., Dominy, W., Kuo, W.C., Horgen, F.D. 2008. Determination of microbial community structures of shrimp floc cultures by biomarkers and analysis of floc amino acid profiles. Aquaculture Research, 39, 118133.

19. Kent, M.., Browdy C.L., Leffler, J.W. 2011. Consumption and digestion of suspended microbes by juvenile Pacific white shrimp Litopenaeus vannamei. Aquaculture. 319: 363-368.

20. Krishna, C., Van Loosdrecht, M.C.M., 1999. Effect of temperature on storage polymers and settleability of activated sludge. Water Res. 33 (10), 23742382.

21. Kuhn, D.D., Boardman, G., Lawrence, A., Marsh, L., Flick, G. 2009. Microbial floc meal as a replacement ingredient for fish meal and soybean protein in shrimp feed. Aquaculture, 296, 5157.

22. Kuhn, D.D, Lawrence, A. 2012. Ex-situ biofloc technology. In: Avnimelech Y, editor. Biofloc Technology - a practical guide book, 2nd ed., The World Aquaculture Society, Baton Rouge, Louisiana, USA. pp. 217-230

23. Kuhn, D.D., Boardman, G.D., Craig, S.R., Flick, Jr.G.J., McLean, E. 2008. Use of microbial flocs generated from tilapia effluent as a nutritional supplement for shrimp, Litopenaeus vannamei, in


63

recirculating aquaculture sistems. J World Aquacult Soc 39:72-82.

24. Lancelot, C., Billen, G. 1985. Carbonnitrogen relationships in nutrient metabolism of coastalarinecosystems. In: Jannasch, H.W., Williams, J. J. L. (Eds.), Advances in Aquatic Microbiology vol.3. AcademicPress, NewYork, USA, pp. 2633210.

25. Maic, P.F., Borba, M.R., Wasielesky, W. 2011. Effect of low salinity on microbial floc composition and performance of Litopenaeus vannamei (Boone) juveniles reared in a zero-water-exchange super-intensive system. Aquaculture Research (online published firstDOI: 10.1111/j.1365-2109.2011.02838.x).

26. McIntosh, R.P. 2000. Changing paradigms in shrimp farming: III. Pond design and operation considerations. Global Aquaculture Advocate, 3:42-44.

27. Metcalf and Eddy, 2003. Wastewater Engineering: Treatment and Reuse, 4th edition.

28. Nielsen, D.L., Brock, M.A., Rees, G.N., Baldwin, D.S. 2003. Effects of increasing salinity on freshwater ecosystems in Australia. Aus J Bot 51:655-665.

29. Nguyn Th Thu Hin. 2012. Bn tin Vin Nghin cu Nui trng Thy sn I, S 8 (2012 - 1/2013): 13-15.

30. Panjaitan, P. 2011. Effect of C:N Ratio Levels on Water Quality and Shrimp Production Parameters in Penaeus monodon Shrimp Culture with Limited Water Exchange Using Molasses as a Carbon Source. ILMU KELAUTAN Maret 2011. Vol. 16 (1) 1-8.

31. Panjaitan, P. 2010. The Penaeus monodon shrimp culture with zero water exchange model using molasses as carbon source. The Study Centre of Anima; Husbandry, Fisheries, Coastal and Marine Resource, Animal Husbandry Faculty, University of HKBP Nommensen, Medan Indonesia.

32. Rittmann, B.E., McCarty, P.L. 2001. Environmental Biotechnology: Principles and Applications. McGraw-Hill, New York. 754 pp.

33. Ronald Lulijwa 2010. Effect of nutrient supplementation on Artemia production in solar salt ponds in the Mekong Delta, Vietnam. MSc thesis, Gent University.

34. Samocha, T.M., Patnaik, S., Speed, M., Ali, A.M, Burger, J.M, Almeida, R.V, Ayub, Z.,

Harisanto, M., Horowitz, A., Brock, D.L. 2007. Use of molasses as carbon source in limited discharge nursery and grow out sistems for Litopenaeus vannamei. Aquac Eng 36:184-191.

35. Soares, R., Jackson, C., Coman, F., Preston, N. 2004. Nutritional composition of flocculated material in experimental zero-exchange system for Penaeus monodon. In: Australian Aquaculture, 2004 WAS, Sydney p.89.

36. Tacon, A.G.J., Cody, J.J., Conquest, L.D., Divakaran, S., Forster, I.P., Decamp, O.E. 2002. Effect of culture system on the nutrition and growth performance of Pacific white shrimp Litopenaeus vannamei (Boone) fed different diets. Aquaculture Nutrition, 8, 121137.

37. Taw, N. 2005. Shrimp Farming in Indonesia, evolving industry responds to varied issues. Global aquaculture advocacate, 8(4), 65-67.

38. Tezuka, Y. 1990. Bacterial regeneration of ammonium and phosphate as affected by the Carbon: Nitrogen: Phosphorus ratio of organic substrates. Microbial Ecology, 19: 227238.

39. Timmons, M.B., Ebeling, H.J., Wheaton, F.W., Summerfelt, S.T., Vinvi, B.J. 2002. Recirculating aquaculture systems, 2nd edition. NRAC Publication, vol. 01-002. 2d Edition. 768 pp.

40. Trn Nguyn Hi Nam, 2012. nh hng ca t l C:N trong ngun thc n b sung ln s pht trin ca vi khun d dng, sn lng v cht lng trng bo xc trong ao nui Artemia. ti cp b. 82 trang.

41. Wasielesky, W.Jr, Atwood, H., Stokes, A., Browdy, C.L. (2006). Effect of natural production in a zero exchange suspended microbial floc based super-intensive culture system for white shrimp Litopenaeus vannamei. Aquaculture, 258, 396403.

42. Widanarni, Ekasari, J., Maryam, S. 2012. Evaluation of Biofloc Technology Application on Water Quality and Production Performance of Red Tilapia Oreochromis sp. Cultured at Different Stocking Densities. HAYATI Journal of Biosciences 19 (2): 73-80.

43. Wilen, B.M., Nielsen, J.L., Keiding, K., Nielsen, P.H., 2000. Influence of microbial activity on the stability of activated sludge flocs. Colloid Surf. B. 18 (2): 145156.

911103biofloc(thai)

Documents