Swine wastewater and biogas technology in Vietnam
Status of pig farming and swine wastewater in Vietnam
Pig farming accounts for about 60% of the value of the Vietnamese livestock industry
The number of pigs increased from 27.4 million in 2017 to 28.1 million in 2018 Pork accounts for about 74% of the total meat consumption in Vietnam (TCTK, 2018)
In 2008, small-scale pig farms accounted for 85% of total pigs and 15% of the total is commercial pig farms (Hoang, 2012) In 2014, 70% of pigs were produced by household farms, the rest were from large-scale commercial pig producers (CCN,
2015) There are 4 million pig farming households in 2014 It is expected that in 2025 this number will decrease by 1.5–2 million households
The transition from traditional pig production to industrial production is creating an increasing amount of pig waste By 2015, pig production has created the highest manure rate (30.3%) (MARD, 2015) Pig manure is not easy to collect because of its slurry form The mass of urine and feces excreted daily by a pig is about 9-11% of its body mass
Table 1.1 The mass of urine and feces excreted daily by a pig
Depending on the method and conditions of livestock production, swine wastewater has different characteristics In swine wastewater, organic compounds account for 70-80% including cellulose, protein, amino acid, fat, carbohydrate, etc, in feces and leftovers Inorganic substances account for 20-30%, the pollution characteristics are shown in detail in the below table:
Table 1.2 The characteristic of swine wastewater
In addition, the feces also contain a variety of bacteria, viruses and parasites In 1kg of feces contain 2000-5000 eggs of helminths (Nguyen, 2004)
Table 1.3 Some microbiological components in pig waste
Along with the tendency of large-scale pig and intensive farming, environmental pollution is becoming more serious due to poor treating of pig waste and inappropriate use of industrial feed Untreated nutrition, antibiotics, and pathogens in pig manure when discharged into the soil and surrounding water, are observe causes of pollution Environmental pollution caused by livestock production is can be the biggest risk to public health.
Environmental impact of swine wastewater
Air pollution consists of bad odors emitted from the decomposition process of organic substances in manure, urine, and leftovers The strength of odors depends on the permissible level of NH3 and H2S are 200 àg/m 3 and 42 àg/m 3 , respectively The concentration of NH3 and H2S in air emitted from pig farm in the North of Vietnam is reported to be 7–18 times higher and 5–50 times higher than the permissible level, respectively (Vu, 2014).A study of environmental pollution caused by livestock in
2009 showed that air pollution (NH3 content) is 18 times higher than the permissible level for household farms and 21 times for large-scale commercial farms (Phung et al., 2009)
Pigs emit about 70 to 90% of nitrogen, minerals and heavy metals in food Direct discharge of swine wastewater into the soil without treatment causes contamination of the receiving soil Lands in areas with a high density of pig farms are being polluted at many levels However, there is still little research and data about this phenomenon (World bank, 2017)
If swine wastewater is not treated well, it will contaminate surface water sources and cause eutrophication The accumulation of pollutants in surface water over a long time may be the cause of the contamination of groundwater due to the permeability process
In terms of microbial contamination, for farm households, the concentration of coliform was 278 times higher than the permissible level (5000 CFU/100 mL) while the industrial farm was 630 times higher than permitted (Phung et al., 2009)
Because of these effects, if swine wastewater is not treat reasonable will greatly affect public health, disease outbreaks in animals, causing serious environmental pollution.
Biogas production technology in Vietnam
Currently, pig manure is treated in many ways, including composting, used for biogas and using fresh manure directly as fertilizer In composting, solid waste is collected and mixed to produce organic fertilizer while the liquid is washed away from the floor and discharged into the surrounding environment or fish pond In the biogas method, swine wastewater is collected and processed in biogas digester, gas generated will be used for cooking and swine wastewater after biogas is used as fertilizer or discharged into fish ponds
In pig production, the use of biogas digesters for swine wastewater treatment is relatively widespread About 53% of industrial farms in the south, 60% in the north and 42% in the central region are reported to have used biogas digesters for swine wastewater treatment (Vu, 2014) The majority of the commercial farms (81%) have a biogas plant for swine wastewater treatment, while only 12.7% of household farm use it (Dinh, 2009)
According to the report of the Vietnam Institute of Animal Husbandry, swine wastewater treatment is often treated by single method This is a big problem because the effluent not meets discharge standards Most pig farms treat wastewater simply and let the wastewater flow freely into the surrounding environment standards Most pig farms treat wastewater simply and let the wastewater flow freely into the surrounding environment Figure 1.1 shows the swine wastewater treatment process popular in Vietnam:
Figure 1.1 Swine wastewater treatment process
Biogas production technologies in Vietnam are design and processing effect different, biogas technologies applied so far is shown in the table 1.4:
Table 1.4 Biogas production technology in Vietnam
Biogas digester with fixed cap (KT1- Chinese technology)
- Materials are brick and cement Volume from 5 to 50m 3 , high durability, gas generated high pressure
- Due to funding from the Netherlands, this type of biogas tunnel is applied in many provinces in Vietnam
- The structure is compact, occupying less construction area, higher cost than other type
- In addition, the cover is quite heavy, easy to rust
Biogas bags made of nylon polyethylence
- Easy installation technique Simple operation and less running costs Because of its low price so alot of households use this type
- The disadvantage is that biogas bags need to avoid sunlight and mechanical damage
- Built of hight quality plastic yarn, make molds with high-tech compressors Meet the technical needs, simple design, lightweight, high gas efficiency, easy to install,
The total number of biogas plant installed in Viet Nam, by type of technology and scale, is shown in table 1.5:
Table 1.5 Biogas plant in Vietnam by type of technology
Type of technology used Large – scale farm
Total number of biogas plant 15370 450000 465370
MBP: Medium Biogas plants have an average volume of 500m 3 ; LBP: Large Biogas plants have an average volume of 2000 m 3 ; SBP: Small Biogas plants have an average volume of 10m 3
According to the study of Nguyen (2012), the effectiveness of biogas digester for swine wastewater treatment is shown in the table 1.6:
Table 1.6 Effectiveness of biogas digester for swine wastewater treatment
Parameter Influent (mg/L) Effluents (mg/L) Efficiency (%)
Due to lack of information, in Vietnam most people are still not aware of all the risks associated with the improper treatment of swine wastewater, the main reason for farmers to build biogas plants is that they want to reduce odor and fly problems (Luu,
2015) Many farmers do not know that wastewater after biogas treatment is not safe
In fact, the biogas plant only reduces the concentration of E coli by 2log10 CFU/mL
The biogas digester sample is still positive for some pathogens that are harmful to humans and exceed national standards for wastewater (MARD, 2013) Total coliforms in swine wastewater after biogas treatment exceeds the permitted level (500CFU/100mL) from 4 to 2200 times BOD5 (100mg/L) and COD levels (300mg/L) from breeding facilities in the north exceed the permitted threshold from
3 to 5 times (Vu, 2014) In order to qualify for discharge into the environment, wastewater should be treated further Wastewater treatment using duckweed systems is considered to be used in the treatment of the organic matter, nutrient and pathogen removal (Smith et al., 2001).
Using duckweed pond system for swine wastewater treatment
General information of duckweed
Duckweed is divided into four genera including Wolffia, Wolffiella, Spirodela, Lemna belongs to the family of the Lemnaceae, so far, about 40 species are known The fronds of Lemna and Spirodela are oval and flat Wolfia fronds are often crescent- shaped while Wolffiella has a boat shape Spirodela has more than two roots on each frond, Lemna has only one Wolffiella and Wolfia do not have roots (Leng, 2017)
Duckweed is the smallest flowering plant, size from 1mm to 1cm, which floats on the water surface They are dependent on nutrition available in the water (Buijzer et al.,
Lemnacae family appears worldwide, but most in subtropical or tropical areas They easily grow in the summer season in temperate and cold areas, however, they are very sensitive to frost Duckweed can survive in both fresh and brackish water They do not live in fast flow water, common in still waters, on mud and a rich source of organic nutrients (Borisjuk et al., 2018)
When there are ideal conditions for pH, light, temperature, and nutrients, duckweed can double their biomass in 16h to 48h When meeting unfavorable conditions such as declining temperature, lack of water, duckweed have a special mechanism to survive by flowering in late summer, producing starchy filled structures and sink to the bottom during the winter until favorable conditions available (Leng, 2017)
In this study, Spirodela polyrhiza were selected The table 1.7 below shows the characteristics of this duckweed:
Table 1.7 The characteristic of Spirodela polyrhiza
Active growth period Spring Foliage porosity summer/winter Porous
After harvest regrowth rate Slow pH 5.0-8.6
C:N ratio Medium Planting density per ha 1080-1920
Flower color Green Bloom period Late summer
Foliage color Green Vegetative spread rate Rapid
Genome size(Mbp) 158 Form turions during winter Yes
The duckweed has been showed that very effective in wastewater treatment, due to they grow rapidly and uptake nutrients, particularly phosphate and nitrogen It is also a source of nutritious food for animals (Ansa et al., 2015), (Chaudhuri et al., 2014).
Factors affecting the growth of duckweed
Duckweed grows in the temperature range of 6-33°C The optimal growth rate when the temperature from 25-31 degrees The treatment efficiency of duckweed is significantly reduced when the temperature is below 17 degrees and above 35 degrees Duckweed can survive in the pH range of 5 to 9 The optimal value is from 6.5 to 7 (Leng, 2017)
Duckweed is very sensitive to the wind, so in very windy regions, wastewater treatment using duckweed pond is not suitable Duckweed will be swept away to the shore of pond by the wind and die, resulting in reduced coverage, enabling algae and mosquitoes to grow (Iqbal, 1999)
The natural habitat of Lemnaceae family is quiescent water bodies so they can only withstand water velocity 8.5) and low pH (8.5) and low pH ( 10% is acceptable, which were calculated by the formula (Martin-Latil et al., 2012):
The recovery of MNV is shown in figure 3.4:
Figure 3.4 The recovery of MNV in CFS
The results show that the recovery of 19/20 samples was acceptable, ranged from 12% to 49%, this means that the proposed procedure was acceptable
Samples collected from the CFS were subjected to analysis, the results showed that:
- The concentration of pathogen parameters in 2 lines is not much different
- Because of low input concentration values, it is difficult to find the trend of FRNA- phages, E coli, Total coliforms
- Other viruses were undetermined except for PMMoV
Therefore, a further experiment was necessary to make clear the role of duckweed in the fate of pathogens, whether duckweed contributes to reducing microbes or viruses in wastewater through attachment to their surfaces or not.
Batch mode system (BMS)
The occurrence of bacterial indicator in batch mode system
The analysis and calculation of E coli and Total coliforms were conducted for 3 zones: (i) Zone 1 (surface zone: duckweed), (ii) Zone 2 (middle water zone) and (iii) Zone 3 (bottom zone: 1cm from the bottom) Results are shown in table 3.5:
Table 3.5 logconcentration (mean ± SD) of E coli and Total coliforms in zone 2 in BMS
E coli (CFU/mL), log concentration (mean ± SD) log Removal
Total coliforms (CFU/mL), log concentration (mean ± SD) log Removal
In the last day of the experiment (HRT = 81h), samples were collected from the surface of DTS and the bottom of all ponds, analysis results may give some image on the distribution of pathogens in duckweed ponds The mean concentrations are shown in the table 3.6 and figure 3.5 - 3.6:
Table 3.6 logconcentration (mean ± SD) of E coli and Total coliforms in zone 1 and zone 3 in BMS log ( E coli ) in zone 3 (CFU/mL) log (TC) in zone 3 (CFU/mL) log ( E coli ) in zone 1 (CFU/g) log (TC) in zone 1 (CFU/g)
Figure 3.5 logconcentration of E coli in BMS
Figure 3.6 logconcentration of Total coliforms (TC) in BMS
In zone 1 of the pond, the concentration of E coli and Total coliforms were 2.79×10 6 CFU/g, 3.74×10 7 CFU/g, respectively
HRT (h) zone 2 - w duckweed zone 2 - wo duckweed zone 3 - w duckweed zone 3 - wo duckweed zone 1 - w duckweed
0 27 54 81 log CFU/g log CFU/mL
HRT(h) zone 2 - w duckweed zone 2 - wo duckweed zone 3 - w duckweed zone 3 - wo duckweed zone 1 - w duckweed
In the zone 2 of the pond, E coli and TC were decreased over time log removal of
E coli and TC in DTS were 1.62log, 1.57 log and 1.15 log, 1.18log in CS, respectively log removals of DTS is a bit better than CS in reduction of E coli and Total coliformss, 0.47 log and 0.39 log, respectively In the study of Elshafai et al.,
2007, TC removal has the logreduction was 4.35 for DTS with HRT = 15 days, in our case HRT ~ 3.4d
In the other hand, E coli and TC also attached to the suspended solid particles then settle to the bottom of the pond, so the concentration of E coli and TC in the bottom layer is higher than in the zone 3 E coli concentration was 3.47×10 8 and 1.44×10 8 CFU/mL, and TC was 2.15×10 9 , 1.79×10 9 CFU/mL, respectively
Compared with CFS, the interpolation values of E coli at HRT = 81h according to graph of E coli concentrationin DTS and CS were 3.53×10 -1 , 4.33×10 0 CFU/mL, respectively log removal of DTS and CS were 3.07 log, 1.98 log, respectively The interpolation values of TC at HRT = 81h according to graph of TC concentrationin DTS and CS were 2.72×10 1 , 5.32×10 1 CFU/mL, respectively log removal of DTS and CS were 1.90 log, 1.60 log, respectively Therefore, log removal in both DTS,
CS of CFS higher than BMS
From the results of samples and the initial concentration (HRT=0), the distribution of
E coli and Total coliforms between three pond’s zones can be calculated as follow:
Amount of E coli /TC/FRNA-phages (initial)
C z1 : Mean concentration of E coli or TC (CFU/g)/or FRNA-phages (PFU/g) in zone
1 (the surface of duckweed), HRT = 81 h m dw: Mean fresh weigh of duckweed in the surface of pond (5.2812g)
C z2 : Mean concentration of E coli/or TC (CFU/mL)/ or FRNA-phages (PFU/mL) in the zone 2, HRT = 81 h
C z3 : Mean concentration of E coli/or TC (CFU/mL)/or FRNA-phages (PFU/mL) in the zone 3, HRT = 81 h
V z3 : Volume of water with the height was 1 cm from the bottom of the pond (mL)
T: The number of E coli/or TC (CFU)/or FRNA-phages (PFU) taken out of sample collection to analyze (table 3.7, table 3.8)
T0, T1, T2, T3: Mean concentration of E coli/or TC (CFU/mL)/or FRNA- phages (PFU/mL) in zone 2 in each time of sample collection, duration between samplings = 27h
V0, V1, V2, V3: Volume of water was taken out in zone 2 in each time to analyze parameters (mL)
TB: Mean concentration of E coli/or TC (CFU/mL)/or FRNA-phages
(PFU/mL) in zone 3, HRT = 81h
VB: Volume of water was taken out in zone 3 (mL)
D: The die off number of E coli/or TC (CFU)/or FRNA-phages (PFU)
In the case of CS, there was no zone 1
Table 3.7 is shown the number of E coli was taken out to analyze in each time sampling
Table 3.7 The number of E coli taken out in each time sampling
Concentration of E coli in DTS (CFU/mL)
E coli was taken out in DTS (CFU)
Concentration of E coli in CS (CFU/mL)
The number of E coli was taken out in
Results of E coli in three zones at HRT = 81h were given in table table 3.8-3.9 and figures 3.7-3.8 below:
Table 3.8 The concentration in different zones of E coli in DTS and CS
Amout of E coli in DTS
Concentration of E coli in CS (CFU/mL)
1 : Amout of E coli in Zone 1 = C z1 (CFU/g) × m dw (g) = CFU
2 : Take out = Total T in table 3.7
According the above results, the distribution of E coli in the pond can be calculated
Table 3.9 is shown the distribution of E coli in DTS and CS
Table 3.9 The distribution of E coli in DTS and CS
Amout of E coli in DTS (CFU)
Fig 3.7 Distribution of E coli in DTS (CFU) Fig 3.8 Distribution of E coli in CS (CFU)
Table 3.10 is shown the number of TC was taken out to analyze in each time sampling
96.51 zone 1 zone 2 zone 3 Die off
Table 3.10 The number of TC taken out in each time sampling
Concentration of TC in DTS (CFU/mL)
TC was taken out in DTS (CFU)
Concentration of TC in CS (CFU/mL)
TC was taken out in
Results of TC in three zones at HRT = 81h were given in table table 3.11 below:
Table 3.11 The concentration in different zones of TC in DTS and CS
TC in DTS (CFU/mL)
Concentration of TC in CS (CFU/mL)
TC in CS (CFU) Initial 0 8000 1.74 × 10 6 1.39 × 10 10 1.63 × 10 6 1.30 × 10 10
1 : Amout of TC in Zone 1 = C z1 (CFU/g) × m dw (g) = CFU
2 : Take out = Total T in table 3.10
According the above results, the distribution of TC in the pond can be calculated
Table 3.12 and figure 3.9-3.10 are shown the distribution of TC in DTS and CS
Table 3.12 The distribution of Total coliforms in DTS and CS
Amout of TC in DTS
% Total Amout of TC in CS
Figure 3.9 Distribution of TC in DTS (CFU) Figure 3.10 Distribution of TC in CS (CFU)
From the distribution of E coli and TC in the different sections of the pond, it is observed that the amount of E coli and TC taken out during multiple sampling after 3.4 days in both systems were similar, by 5.38 × 10 8 and 6.49 × 10 8 CFU/mL for E coli, 1.50 × 10 9 and 1.72 × 10 9 CFU/mL for TC, respectively
The distribution of E coli and Total coliforms at DTS in zone 3 were also lower than that of CS The of E coli and Total coliforms attached to the duckweed on the surface was very small, 0.14% and 1.6%, respectively The most obvious thing is that the reduction of E coli and TC was mostly due to the die off
There have not been many studies on the mechanism of the effects of the duckweed on pathogens, therefore more specific studies are needed.
The occurrence of viral indicator in batch mode system
In this experiment, FRNA-phages were possitive in all samples The analysis results and calculation of FRNA-phages is show in the table 3.9 and figure 3.11:
Table 3.13 The mean concentration of FRNA-phages in water layer of BMS
FRNA-phages (PFU/mL), log concentration (mean ± SD) log
81.5 zone 1 zone 2 zone 3 Die off
Figure 3.11 log concentration of FRNA-Phages
FRNA-phages distribution also tends to be similar to E coli and Total coliforms, they were reduced over time
In the surface of duckweed, the concentration of FRNA-phages was 1.12×10 7 PFU/g
This proves that a part of FRNA-phages has attached to duckweed in the surface
In the zone 2 of the pond, during operation the system, the logreduction of FRNA- phages in the middle water zone was 3.4 log for DTS, 1.95 log for CS The log reduction of FRNA phages in DTS was higher than the control 1.45 log
FRNA-phages also attached to the suspended solid particles then settle to the bottom of the pond
Table 3.14 is shown the number of FRNA-phages was taken out to analyze in each time sampling
Table 3.14 The number of FRNA-phages taken out in each time sampling
Concentration of FRNA- phages in DTS (PFU/mL)
The number of FRNA-phages was taken out in DTS (PFU)
Concentration of FRNA- phages in CS (PFU/mL)
The number of FRNA- phages was taken out in
HRT (h) zone 2 - w duckweed zone 2 - wo duckwedd zone 3 - w duckweed zone 3 - wo duckweed zone 1 - w duckweed
Results of FRNA-phages in three zones at HRT = 81h were given in table table 3.15 below:
Table 3.15 The concentration in different zones of FRNA-phages in DTS and CS
Concentration of FRNA-phages in DTS (PFU/mL)
Amout of FRNA- phages in DTS (PFU)
Concentration of FRNA- phages in CS (PFU/mL)
Amout of FRNA- phages in
1 : Amout of FRNA-phages in Zone 1 = C z1 (CFU/g) × m dw (g) = CFU
2 : Take out = Total T in table 3.14
According the above results, the distribution of FRNA-phages in the pond can be calculated Table 3.16 and figure 3.12-3.13 are shown the distribution of TC in DTS and CS
Table 3.16 The distribution of FRNA-phages in DTS and CS
Amout of FRNA-phages in DTS (CFU)
% Total Amout of FRNA-phages in CS (CFU)
Fig 3.12 Distribution of FRNA-phages in DTS (PFU) Fig 3.13 Distribution of FRNA-phages in CS (PFU)
99.96 zone 1 zone 2 zone 3 Die off
The amount of FRNA-phages in three zone of the pond in both DTS and CS was very low The amount of FRNA-phages attached to duckweed on the surface very small, the distribution rate was 0.0001% The main cause of reduced FRNA-phages concentration in DTS and CS were due to the die-off b) PMMoV
In this experiment, PMMoV wasn't spiked into the system The result in table 3.18 is the log concentration of PMMoV available in wastewater, 17/30 samples were positive when detected by q-PCR
Table 3.17 log concentration (mean ± SD) of PMMoV in zone 2,3 of BMS
PMMoV in the middle layer (copies/L), log concentration
PMMoV in zone 3 (copies/L) log concentration (mean ± SD)
1 : Only one sample log concentration of PMMoV is shown in the figure 3.14:
Figure 3.14 log concentration of PMMoV
HRT (h) zone 2 - w duckweed zone 2 - wo duckweed zone 3 - w duckweed zone 3 - wo duckweed
PMMoV was detected in the samples with the reducing concentrations along the time in DTS was similar with in CS, by 0.15 log and 0.14 log PMMoV PMMoV was decreased over time due to die off and the other factors impacted on them Since the results have not been repeated, the impact of DTS on PMMoV needs further study
Compared with CFS, the interpolation values of PMMoV at HRT = 81h according to graph of PMMoV concentrationin DTS and CS were 6.83×10 3 , 9.52×10 3 copies/L, respectively log removal of DTS and CS were 0.3 log, 0.2 log, respectively
Therefore, log removal of PMMoV in both DTS, CS of CFS higher than BMS.
Positive control
MNV virus was added in RNA extraction step The results of recovery of MNV were given in figure 3.15 Fig 3.15 shows that the recovery of 28/30 samples are acceptable, ranged from 11% to 35% MNV is a process control very usefull because it can provide the efficiency of RNA extraction and virus concentration
Figure 3.15 The recovery of MNV
Other parameters
TN, TP in CFS
TN and TP were analyzed during the sampling of the CFS The concentration of Total Nitrogen, Total Phosphorus are shown in figure 3.16 and 3.17, respectively:
Figure 3.16 Concentration of TN of CFS (mg/L)
Figure 3.17 Concentration of TP of CFS (mg/L)
The interpolation values of TN, TP, PO4 3- at HRT = 81h according to graph of them concentration in DTS were 49.78 mg/L, 5.621 mg/L, 0.95 mg/L and in CS were 67 mg/L, 8.364 mg/L, 1.21 mg/L, respectively
In the continuous flow system, the DTS was highly capable of removing organic matter as well as nutrients The DTS removal efficiency of, TN, TP, PO4 3- at HRT 100.8 were 49%, 48%, 38% respectively This similar to the study of Leng, 2017 (removal efficiency of TN = 50%, TP = 48.4%), but there was no mention about HRT
Removal in CS of TN, TP were 30%, 20%, 21%, respectively Therefore, DTS treatment efficiency was higher than CS.
pH, ammonium, Turbidity in CFS and BMS
In BMS, the values of pH at HRT = 81h in DTS and CS were: 7.86 and 8.06, respectively In CFS, the interpolation values of pH at HRT = 81h according to graph of pH values in DTS and CS were 6.73, 7.03, respectively The results are shown in figure 3.20 and figure 3.21
Figure 3.19 pH in CFS Figure 3.20 pH in BMS
Along the time, in both systems, CFS and BMS, the pH decreased gradually It may be due to the nitrification In both systems, DTS had stronger pH reduction as compared with CS This phenomenon may be explained by the existence of duckweed root system, it may serve as a microbial carrying material, then microbial nitrification was stronger than in CS, the consequence was that DTS pH was lower than that of
In BMS, the values of NH4 +-N at HRT = 81h in DTS and CS were: 46.89 mg N/L and 52.19 mg N/L, respectively The removal efficiency of NH4 +-N in DTS and CS at HRT = 81h were 33% and 24%, respectively
In CFS, the interpolation values of NH4 +-N at HRT = 81h according to graph of NH4 +-
N in DTS and CS were 9.79 mg N/L and 19.42 mg N/L, respectively The removal efficiency of NH4 +-N in DTS and CS at HRT = 81h were 79% and 59%, respectively
Therefore, the removal efficiency of NH4 +-N in CFS higher than BMS
The results are shown in figure 3.20 and figure 3.2
Fig 3.21 Concentration of N-NH 4 + in CFS (mg/L) Fig 3.22 Concentration of N-NH 4 + in BMS (mg/L)
Duckweed exposed to both Ammonium-N and Nitrate-N and it preferably uptake for ammonium So that in ponds with duckweed the concentration of ammonium was lower than in ponds without duckweed Then, ammonium reduction in DTS was also higher than the controls in both configurations c) Turbidity
In BMS, the values of turbidity at HRT = 81h in DTS and CS were: 9.5 NTU and 9 NTU, respectively The removal efficiency of turbidity in DTS and CS at HRT = 81h were 95% and 96%, respectively
In CFS, the interpolation values of turbidity at HRT = 81h according to graph of turbidity in DTS and CS were 2.05 NTU and 3.23 NTU, respectively The removal efficiency of turbidity in DTS and CS at HRT = 81h were 93% and 88%, respectively
Figure 3.23 Turbidity in CFS Figure 3.24 Turbidity in BMS
Turbidity also decrease steadily Turbidity were similar between two systems This shows that the turbidity decreases mainly due to sedimentation
From results and discussion part, the following conclusions may be made:
1a) For CFS, this study found quantitative values of 3 pathogen parameters for 2 systems DTS and CS:
E coli, DTS, HRT = 100.8h (81h * ) = 5×10 -1 (3.53×10 -1 ) CFU/mL
E coli, CS, HRT = 100.8h (81h * ) = 5×10 -1 (4.33×10 0 ) CFU/mL
TC, DTS, HRT = 100.8h (81h * ) = 2.91×10 1 (2.72×10 1 ) CFU/mL
TC, CS, HRT = 100.8h (81h * ) = 1.89×10 1 (5.23×10 1 ) CFU/mL PMMoV, DTS, HRT = 100.8h (81h * ) = 3.94×10 3 (6.82×10 3 ) copies/L PMMoV, CS, HRT = 100.8h (81h * ) = 9.31×10 3 (9.52×10 3 ) copies/L FRNA-phages, and other viruses HEV, NoV GII, FRNA-GI were too low to be quantified
1b) For BMS, this study found quantitative values of 4 parameters:
E coli, DTS, zone 1, HRT = 81h: 2.79×10 6 CFU/g
E coli, DTS, zone 2, HRT = 81h: 3.47× 10 4 CFU/mL
E coli, CS, zone 2, HRT = 81h: 8.75 × 10 4 CFU/mL
E coli, DTS, zone 3, HRT = 81h: 3.57× 10 5 CFU/mL
E coli, CS, zone 3, HRT = 81h: 8.58 × 10 5 CFU/mL
TC, DTS, zone 1, HRT = 81h: 3.74 × 10 7 CFU/g
TC, DTS, zone 2, HRT = 81h: 4.67 × 10 4 CFU/mL
TC, CS, zone 2, HRT = 81h: 1.08 × 10 5 CFU/mL
TC, DTS, zone 3, HRT = 81h: 4.42 × 10 6 CFU/mL
TC, CS, zone 3, HRT = 81h: 5.36 × 10 6 CFU/mL FRNA-phages, DTS, zone 1, HRT = 81h: 2.12 × 10 6 PFU/g FRNA-phages, DTS, zone 2, HRT = 81h: 7.17 × 10 5 PFU/mL FRNA-phages, CS, zone 2, HRT = 81h: 2.02 × 10 7 PFU/mL FRNA-phages, DTS, zone 3, HRT = 81h: 1.47 × 10 6 PFU/mL FRNA-phages, CS, zone 3, HRT = 81h: 1.39 × 10 7 PFU/mL
PMMoV, DTS, zone 2, HRT = 81h: 5.53×10 3 copies/L PMMoV, CS, zone 2, HRT = 81h: = 7.24×10 3 copies/L PMMoV, DTS, zone 3, HRT = 81h: 2.26×10 3 copies/L PMMoV, CS, zone 3, HRT = 81h: = 1.36×10 3 copies/L
The results above show that a part of the microorganism has attached to duckweed on the surface Almost concentration values of E coli, Total coliform, FRNA-phages, PMMoV in DTS lower than in CS
2a) log Removal of 2*2 systems, 3 pathogen parameters in CFS, 4 in BMS were analyzed:
In CFS, HRT = 81 h log Removal for E coli: 3.07 log, 1.98 log, in DTS and CS, respectively log Removal for TC: 1.90 log, 1.60 log, in DTS and CS, respectively log Removal for PMMoV: 0.3 log, 0.2 log, in DTS and CS, respectively
In BMS, HRT = 81 h log Removal for E coli: 1.62 log, 1.15log, in DTS and CS, respectively log Removal for TC: 1.57 log, 1.18 log, in DTS and CS, respectively log Removal for FRNA-pahes: 3.40 log, 1.15 log, in DTS and CS, respectively log Removal for PMMoV: 0.15 log, 0.14 log, in DTS and CS, respectively
Therefore, the reduction of E coli, Total coliforms, PMMoV in continuous flow system seemed to be higher than batch mode system
2b) Distribution of pathogens in pond depends strongly on conditions in which they are being treated This study successful in defining the distribution of pathogens in 3 zones of BMS with spiking Quantitative values of 3 pathogen parameters, except the quantity taken off during samplings, are:
E coli were distributed, % = 0.14, 2.03, 1.33, 96.51, in zone 1, 2, 3, and die-off respectively
TC were distributed, % = 1.6, 2.6, 14.4, 81.5, in zone 1, 2, 3, and die-off respectively FRNA-phages were distributed, % = 0.0001, 0.03, 0.004, 99.96, in zone 1, 2, 3, and die-off respectively
E coli were distributed, % = 5.93, 3.73, 90.34 in zone 2, 3, and die-off respectively
TC were distributed, % = 6.5, 19.2, 74.3, in zone 2, 3, and die-off respectively FRNA-phages were distributed, % = 1.33, 0.05, 98.61, in zone 2, 3, and die-off respectively
3) Other parameters in DTS and CS, HRT = 81h
Log removal of pathogen parameters was presented in 2a)
In CFS: pH equals to 6.73, 7.03, in DTS and CS, respectively The removal efficiency of NH4 +-N equals to 33% and 24%, respectively
In BMS: pH equals to 7.86, 8.06, in DTS and CS, respectively The removal efficiency of NH4 +-N equals to 79% and 59%, respectively
The chemical parameters and physical parameters of both systems were significantly reduced
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