A study to use activated sludge anaerobic combining aerobic for treatment of high salt seafood processing wastewater

llutants and shortening the processing time. The experiment was conducted when the active 
sludge content in anaerobic tank was fixed to 8000 mg/L and changed the activated sludge content 
in aerobic tank with values of 4000 mg/L, 6000 mg/L and 8000 mg/L. The retention time of 
anaerobic period is 16 hours, the aerobic time is 6 hours in (Fig. 6). 
Fig 6. Effect of the activated sludge content to efficiency COD, NH4+ and PO43- 
 In Fig. 6, with activated sludge content of 4000 mg/L, the processing efficiency of COD, NH4+ 
and PO43- the whole process is 91.25%; 75.83%; 45.63%, the output value is 168 mg/L, 36.5 
mg/L, respectively and 27.3 mg/L has not met the output standard. With activated sludge content 
of 6000 mg/L, the processing efficiency of COD, NH4+ and PO43- the whole process is 97.32%; 
94.54%; 87.56%, output values are 54 mg/L, 7.1 mg/L and 4.2 mg/L. The treatment efficiency is 
higher than the activated sludge content of 4000 mg/L. Output parameter values have reached the 
output standard. When increasing activated sludge content to 8000 mg/L, COD and NH4+ 
treatment efficiency increased to 97.42% and 95.03%. In general, the higher the mud content, the 
better the performance. However, the activated sludge content of 6000 mg/L and 8000 mg/L has 
no significant difference in treatment performance. Thus, the sludge content of 6000 mg/L in 
aerobic tank is suitable for treatment because if the activated sludge is too high, then handling the 
excess sludge is also a problem. 
2.5 Study on supplementation of saline microorganisms to improve processing efficiency 
 Salt concentrations above 2% (20 g/L NaCl) in the wastewater will affect the growth of the bacteria. 
Study from Joong et al.24 in the experiment for examination of the salt effect on cellular growth shows 
that there was no effect on cellular growth at concentrations of 1% and 2% NaCl, but they observed 
that there was an effect on cellular growth at the concentration of 3.5% NaCl. Burnett22 reported that 
operation of activated sludge process at salt contents higher than 20 g/L was characterized by poor 
flocculation, high effluent solids, and a severe decrease in substrate utilization rate. Hamoda and Al-
Attar25 reported on the effect of standard sodium chloride on aerobic activated sludge treatment 
 84
processes. They demonstrated that no decrease in wastewater treatment performance was observed at 
concentrations approaching 3% NaCl (w/w). The saline microorganism of Bacillus velezensis was 
isolated from the sea of the Institute of Natural Products Chemistry. Surveying the concentration 
of microorganisms favoring salinity from 3 - 10% (density of microbial cells equivalents to 104 
CFU/mL) added to the wastewater treatment process had a salinity level of 3%. The result is given 
in Fig. 7 as follows: 
Fig. 7. Effect of ration Bacillus velezensis additional to processing efficiency 
 The results show that treatment efficiency was directly proportional to increasing microbial 
concentration. However, at a high rate of supplementation (7-10%), treatment efficiency increased 
but not significantly. The reason is that the nutrients in the environment are exhausted. The 
appropriate percentage of additional microorganisms for treatment is determined at 7%. The 
quality of wastewater after treatment with anaerobic activated sludge combining aerobic with 
additional saline microorganisms the output standard according to QCVN 11-MT: 2015 / BTNMT 
(column B). However, as the concentration of salinity exceeds this limit, the tendency of bacteria 
aggregation or adsorption decreases26,27. 
Fig. 8. The quality of waste water after treatment with anaerobic activated sludge system 
combining aerobic with added saline microorganisms 
3. Conclusions 
 The results of this study have been useful for determining the optimum operational conditions 
for seafood processing wastewater treatment by method biological. The biological continuous 
flow system should minimize the amounts of pollutants in the effluent water to reduce 
environmental contaminant levels and to improve the seafood processing effluent water quality so 
that it could be reused and protect the environment quality. 
Acknowledgement 
 The paper has been completed with the financial support of Ministry of Industry and Trade 
T. T. H. Pham and T. M. H. Nguyen / Current Chemistry Letters 9 (2020) 
85
(Vietnam), ĐTKH.072/18. 
4. Experimental section 
Material and methods 
4.1 Seafood processing wastewater preparation 
 The major types of wastes found in seafood-processing wastewaters are blood, offal products, 
viscera, fins, fish heads, shells, skins, and meat “fines”. These wastes contribute significantly to 
the suspended solids concentration of the waste stream. However, most of the solids can be 
removed from the wastewater and collected for animal food applications. Wastewaters from the 
production of fish meal, solubles, and oil from herring, menhaden. However, the degree of 
pollution of a wastewater depends on several parameters. The most important factors are the types 
of operation being carried out and the type of seafood being processed. 
 Fish processing wastewater and fish blood were collected from the processing of edible fish 
species, which were purchased from a local fish market. The processing of fish involves hand-
skinning, filleting, and washing with tap water. The fish processing wash water and fish blood 
were collected immediately in a beaker and homogenized by agitation on the stirrer plate for 30 
min. The wastewater was then kept in a polyethylene bottle and subsequently stored in the freezer 
below 00C for future use. To make the influent for feeding into the bioreactor, the raw wastewater 
was diluted with distilled water to achieve the required concentration. The wastewater from 
seafood processing with the chemical input parameters of pH = 7-8.5, COD = 2000 mg/L, total 
nitrate nitrogen = 150 mg / L, NH4+ = 90 mg/L, total phosphorus=50 mg/L8,9 and at different salt 
concentrations (0.5%, 1.0%, 1.5%, 2.0%, 3.0%, 4.0%, 4.5%, 5.0% w/v NaCl) and without salt 
content (0.0% w/v NaCl)11,12.The wastewater used as feed was maintained in a refrigerator at 40C. 
It was maintained in a feed reservoir and mixing was applied manually at regular intervals. 
4.2 Biological treatment 
 The biological treatment was applied to the seafood processing wastewater after 
sedimentation/flotation and coagulation/flocculation steps in order to evaluate the organic matter 
removal efficiency by activated sludge. The experiments for this study were performed in a 
biological system that consists of a 7.5 L feed tank containing the wastewater to be treated, an 
anaerobic and an aeration tank, height (H) 30,5 cm, edge 15.5cm working volume (V) 5 L. 
Fig 9. Anaerobic tanks and SBR used in the study 
 86
4.3 Activated Sludge Systems 
 In an activated sludge treatment system, an acclimatized, mixed, biological growth of 
microorganisms (sludge) interacts with organic materials in the wastewater in the presence of 
excess dissolved oxygen and nutrients (nitrogen and phosphorus). The microorganisms convert 
the soluble organic compounds to carbon dioxide and cellular materials. 
 Most of the activated sludge systems utilized in the seafood-processing industry are of the 
extended aeration types: that is, they combine long aeration times with low applied organic 
loadings. The detention times are 1 to 2 days. The suspended solids concentrations are maintained 
at moderate levels to facilitate treatment of the low-strength wastes, in experiment have used 
aerobic activated sludge available at the laboratory of Material Technology Center, Institute of 
Applied Technology, activated sludge is fed by domestic wastewater, has yellow brown color, 
activated sludge concentration about 6000 mg/L, with the ratio of MLVSS/MLSS 0.7 - 0.8. 
Besides, we have used Anaerobic sludge Obtaining from anaerobic BHT tank at the Institute of 
Environmental Science and Technology, Hanoi University of Science and Technology. Anaerobic 
sludge is black, BHT concentration is about 8000 - 10000 mg / L, with MLVSS/MLSS ratio 0.7 - 
0.75. 
4.4 Analytical methods 
 Standard Methods for the Examination of Water and Wastewater were adopted for the 
measurement in Table 1 28,29. 
Table 1. Measurement used for examination of water and wastewater 
Parameters Analytical methods Equipment and machinery used 
pH TCVN 6492:2011 (ISO 10523:2008) PH measurement electrode (E01581 Thermo, USA) 
COD Standard method (5220 D), Heating block (DRB200, USA); Photometric machine (Thermo Scienfic, USA) 
Total Nitrogen Persulfate Digestion HACH DR 6000 
NH4+-N Standard method (4500-NH3, F) Ammonium measuring electrode (E01581 Thermo, USA) 
Total Phosphorus Molybdovanadate uses TNT pipes HACH DR6000 
DO TCVN 6001-2:2008 (ISO 5815-2:2003) Máy YSI – 5000 (Mỹ) 
Turbidity USEPA Method 180.1 Turbidity meter HI 98703 (Hanna, Italy) 
SS, MLSS TCVN 6625:2000 (ISO 11923:1997) Drying oven (Daihan / Korea), analytical (HR 200, Japan) 
Salinity Salinity and EXTECH temperature meter EC170 
 The reported values represent the average of at least two measurements; in most cases each 
sample was injected three times, validation being performed by the apparatus only if the 
coefficient of variation (CV) was smaller than 5%. 
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