The present study aims to investigate the influence of Staphylococcus aureus, Escherichia coli and Enterococcus faecalis in public market wastewater on the removal of nutrients in terms of ammonium (NH4–) and orthophosphate (PO43) using Scenedesmus sp. The removal rates of NH4– and orthophosphate PO43– and batch kinetic coefficient of Scenedesmus sp. were investigated. The phycoremediation process was carried out at ambient temperature for 6 days. The results revealed that the pathogenic bacteria exhibited survival potential in the presence of microalgae but they were reduced by 3–4 log at the end of the treatment process. The specific removal rates of NH4– and PO43– have a strong relationship with initial concentration in the public market wastewater (R2 = 0.86 and 0.80, respectively). The kinetic coefficient of NH4– removal by Scenedesmus sp. was determined as k = 4.28 mg NH4– 1 log10 cell mL–1 d–1 and km = 52.01 mg L–1 (R2 = 0.94) while the coefficient of PO43– removal was noted as k = 1.09 mg NH4– 1 log10 cell mL–1 d–1 and km = 85.56 mg L–1 (R2 = 0.92). It can be concluded that Scenedesmus sp. has high competition from indigenous bacteria in the public market wastewater to remove nutrients, with a higher coefficient of removal of NH4– than PO43.
INTRODUCTION
Public market wastewater is defined as the wastewater generated from fish cleaning, washing floors and raw materials as well as melting ice packs. The public market wastewater is also contaminated with blood residues from fish or meat (Verheijen et al. 1996). Public market facilities are provided by the local government for a variety of daily necessities, especially raw goods at reasonable prices.
Public markets represent one of the main significant challenges for environmental issues due to the relatively high constituents of organic matter which may reach the range of 71 and 122 mg/L for biological oxygen demand (BOD) and 381–560 mg/L for chemical oxygen demand (COD) (Zulkifli et al. 2012). Both COD and BOD result in the decrease of dissolved oxygen (DO) levels in the public market wastewater receiving water bodies because the oxygen available in the water is being consumed by the bacteria. Therefore, the direct discharge of these wastes without prior treatment into the environment negatively affects the biological diversity in the environment and natural water bodies due to the decrease of DO necessary for survival of organisms (ReVelle & ReVelle 1998).
Discharge of public market wastewater into aquatic bodies poses a serious eutrophication threat, leading to slow degradation of the water resources. Jais et al. (2017) indicated that the high levels of nutrients in the public market wastewater, which included the presence of phosphates and nitrates, lead to pollution and hypertrophication because the nutrients improve the microalgae growth which causes the water bloom. The adverse effects associated with eutrophication include the reduction of biodiversity and replacement of dominant species, increased water toxicity, turbidity and lifespan of the lakes. Therefore, the nutrient pollutants in the public market wastewater must be reduced before being discharged to prevent undesirable effects (Ruiz-Martinez et al. 2012).
Phycoremediation of wastewater is a green technology and eco-friendly process with no secondary pollution or chemical additives. The process relies on the algae that have the potential to assemble nutrients from the wastewater (Prajapati et al. 2013). However, the efficiency of phycoremediation is dependent on the nature of the relationship between microalgae species introduced into the wastewater and the indigenous organisms such as bacteria (Rhee 1972). The public market wastewater has high loads of bacterial species resulting from the washing process of meat, chicken, fish and vegetables. The high content of nutrients in the public market can also support the bacterial growth. Therefore, the presence of bacteria in these wastes may negatively or positively affect the phycoremediation process. Meanwhile, phycoremediation may cause significant changes in the concentrations of those bacteria.
Ma et al. (2014) stated that the bacteria and algae in the co-existing system have a mutually beneficial relationship where bacteria can help degrade unruly compounds to ammonium, nitrogen, phosphate and carbon dioxide, which can easily be used by algae. In contrast, microalgae cells produce the oxygen required by the aerobic bacteria to mineralize organic pollutants (McGriff & McKinney 1972; Oswald 1988). Nonetheless, both bacteria and microalgae cells have a negative effect against each other. Several bacterial species such as Bacillus sp., Pseudomonas sp. and Aeromonas sp. have high algicidal agent production (Sakata et al. 2011). Algicidal agents are biochemical substrates produced by some bacterial species as a result of the competitive interactions between bacteria and toxic algae. In contrast, Syed et al. (2015) indicated that Chlorella vulgaris has antimicrobial activity against Klebsiella sp., Scenedesmus sp., Microcystis sp., Oscillatoria geminate and C. vulgaris while Nostoc sp. exhibited antimicrobial activity against Staphylococcus aureus, B. subtilis, Sarcina lutea, Klebsiella pneumoniae and B. megaterium (Olfat et al. 2014). So far, many factors include nutrient availability, mixing conditions, light and temperature play an important role in the interactions between algae and bacteria in the environment (Granéli et al. 2008).
The present study aims to determine the bacterial load available in the public market wastewater as well as investigate the influence of bacterial activity on the efficiency of phycoremediation of public market wastewater.
MATERIALS AND METHODS
Sampling
Grab sampling was used for the collection of public market wastewater in which one sample was collected at a specific time. The samples were collected in 5 L polyethylene container bottles at 9 am, which represents the peak time for high production of public market wastewater. These containers were used to avoid the negative effects on analytical parameters as recommended by APHA (2005). The samples were obtained from the discharge point where the effluent is thoroughly mixed and close to the discharging public market outlet. The collected samples were immediately transferred into the laboratories and analysed for all parameters according to APHA (2005).
Chemical and microbiological characteristics of public market wastewater
The characteristics of wastewater including pH, DO, ammonium (NH4–) and orthophosphate (PO43–) were conducted as described by APHA (2005). The pH was determined by using the 4500–H-B method with an Oakton pH 700 Benchtop Meter (Oakton, USA). NH4– was measured according to the 4500-NH4–-B method using the DR 5000 Spectrometer (UV-VIS Hach, USA) while PO43– was determined based on method 1060. Escherichia coli, Enterococcus faecalis and S. aureus were enumerated by the direct plating technique on appropriate selective media (APHA 1999; HPC 2004). The viable count was calculated per plate and followed by 100 mL of the original sample in terms of log10 CFU of the bacteria per 100 mL of public market wastewater sample.
Microalgae strain
Scenedesmus sp. (Accession No. JQ315576.1) is an indigenous strain isolated from freshwater (Table 1). In order to identify the strain based on 18S rRNA sequencing, a pure culture of microalgae on Bold Basal medium (BBM) was sent to Axil Scientific Pte Ltd (The Gemini, Singapore). The microalgae inoculum was prepared by sub-culturing in a BBM broth and incubated at room temperature (25 ± 2 °C, 12 h L:12 h D period) for 7 days as described by Bischoff & Bold (1963). The culture medium was centrifuged (6,000 rpm) to separate the microalgae cells; and the media residue was removed by washing using sterilized deionized water. The microalgae cells were then suspended in 10 mL of sterilized normal saline water. The concentrations of the cells were counted using a haemocytometer. Three inoculum concentrations were prepared with concentrations of 7, 8 and 9 log10 cells mL–1.
Accession number of Scenedesmus sp
Description . | Max score . | Total score . | Query cover . | E value . | Ident . | Accession . |
---|---|---|---|---|---|---|
Scenedesmus sp. KMMCC 1534 18S ribosomal RNA gene, partial sequence | 3,528 | 3,528 | 70% | 0.0 | 98% | JQ315576.1 |
Scenedesmus sp. KMMCC 1533 18S ribosomal RNA gene, partial sequence | 2,165 | 3,023 | 56% | 0.0 | 99% | JQ315577.1 |
Scenedesmus sp. KMMCC 178 18S ribosomal RNA gene, partial sequence | 2,159 | 3,017 | 56% | 0.0 | 99% | JQ315566.1 |
Scenedesmus sp. KMMCC 406 18S ribosomal RNA gene, partial sequence | 2,154 | 3,017 | 56% | 0.0 | 99% | JQ315581.1 |
Scenedesmus sp. KMMCC 1211 18S ribosomal RNA gene, partial sequence | 2,146 | 2,993 | 56% | 0.0 | 99% | JQ315570.1 |
Scenedesmus sp. KMMCC 406 18S ribosomal RNA gene, partial sequence | 2,154 | 3,017 | 56% | 0.0 | 99% | JQ315581.1 |
Scenedesmus sp. KMMCC 872 18S ribosomal RNA gene, partial sequence | 2,154 | 3,017 | 56% | 0.0 | 99% | JQ315579.1 |
Scenedesmus sp. KMMCC 1258 18S ribosomal RNA gene, partial sequence | 2,154 | 3,017 | 56% | 0.0 | 99% | JQ315574.1 |
Scenedesmus sp. KMMCC 1211 18S ribosomal RNA gene, partial sequence | 2,146 | 2,993 | 56% | 0.0 | 99% | JQ315570.1 |
Scenedesmus sp. UKM 9 18S ribosomal RNA gene, partial sequence | 2,141 | 3,065 | 57% | 0.0 | 99% | KU170547.1 |
Scenedesmus sp. KMMCC 1297 18S ribosomal RNA gene, partial sequence | 2,135 | 2,993 | 56% | 0.0 | 99% | JQ315599.1 |
Scenedesmus armatus isolate B 18S ribosomal RNA gene, partial sequence | 2,121 | 3,121 | 58% | 0.0 | 99% | KR082490.1 |
Scenedesmus sp. Lake Las Vegas 18S ribosomal RNA gene, partial sequence | 2,111 | 3,049 | 57% | 0.0 | 99% | JX910112.1 |
Scenedesmus abundans 18S ribosomal RNA gene, partial sequence | 2,065 | 2,868 | 53% | 0.0 | 99% | KT868823.1 |
Description . | Max score . | Total score . | Query cover . | E value . | Ident . | Accession . |
---|---|---|---|---|---|---|
Scenedesmus sp. KMMCC 1534 18S ribosomal RNA gene, partial sequence | 3,528 | 3,528 | 70% | 0.0 | 98% | JQ315576.1 |
Scenedesmus sp. KMMCC 1533 18S ribosomal RNA gene, partial sequence | 2,165 | 3,023 | 56% | 0.0 | 99% | JQ315577.1 |
Scenedesmus sp. KMMCC 178 18S ribosomal RNA gene, partial sequence | 2,159 | 3,017 | 56% | 0.0 | 99% | JQ315566.1 |
Scenedesmus sp. KMMCC 406 18S ribosomal RNA gene, partial sequence | 2,154 | 3,017 | 56% | 0.0 | 99% | JQ315581.1 |
Scenedesmus sp. KMMCC 1211 18S ribosomal RNA gene, partial sequence | 2,146 | 2,993 | 56% | 0.0 | 99% | JQ315570.1 |
Scenedesmus sp. KMMCC 406 18S ribosomal RNA gene, partial sequence | 2,154 | 3,017 | 56% | 0.0 | 99% | JQ315581.1 |
Scenedesmus sp. KMMCC 872 18S ribosomal RNA gene, partial sequence | 2,154 | 3,017 | 56% | 0.0 | 99% | JQ315579.1 |
Scenedesmus sp. KMMCC 1258 18S ribosomal RNA gene, partial sequence | 2,154 | 3,017 | 56% | 0.0 | 99% | JQ315574.1 |
Scenedesmus sp. KMMCC 1211 18S ribosomal RNA gene, partial sequence | 2,146 | 2,993 | 56% | 0.0 | 99% | JQ315570.1 |
Scenedesmus sp. UKM 9 18S ribosomal RNA gene, partial sequence | 2,141 | 3,065 | 57% | 0.0 | 99% | KU170547.1 |
Scenedesmus sp. KMMCC 1297 18S ribosomal RNA gene, partial sequence | 2,135 | 2,993 | 56% | 0.0 | 99% | JQ315599.1 |
Scenedesmus armatus isolate B 18S ribosomal RNA gene, partial sequence | 2,121 | 3,121 | 58% | 0.0 | 99% | KR082490.1 |
Scenedesmus sp. Lake Las Vegas 18S ribosomal RNA gene, partial sequence | 2,111 | 3,049 | 57% | 0.0 | 99% | JX910112.1 |
Scenedesmus abundans 18S ribosomal RNA gene, partial sequence | 2,065 | 2,868 | 53% | 0.0 | 99% | KT868823.1 |
Experimental set up of batch reactor system
Factorial complete randomized design (33
2) in triplicate was used to study the influence of pathogenic bacterial activity on phycoremediation of public market wastewater. Three experimental batch reactors were inoculated with Scenedesmus sp. (7, 8 and 9 log10 cells mL–1) and supplied with an air pump. Two of the experimental batch reactors were used as control; one batch reactor without Scenedesmus sp. was used as the control (CB) to investigate the response of pathogenic bacteria during the phycoremediation of public market wastewater while the other batch reactor contains autoclaved public market wastewater (to inactivate the pathogenic bacteria) inoculated with Scenedesmus sp. (7 log10 cell mL–1) which was used as control (CA) to study the efficiency of the phycoremediation process in the absence of indigenous pathogenic bacteria.
The experimental batch reactors were incubated for 6 days in an open area where direct sunlight is available as needed for microalgae growth. Four litres of raw public market wastewater samples were transferred into each reactor and inoculated in a separate mode with three concentrations of Scenedesmus sp. (7, 8 and 9 log10 cells 100 mL–1). The values of the pathogenic bacteria (E. coli, E. faecalis and S. aureus), pH, DO, ammonium (NH4–) and orthophosphate (PO43–) in the raw public market wastewater were used as initial concentrations. The bacterial and microalgae density as well as the values of pH, DO, NH4– and orthophosphate (PO43–) during the phycoremediation process were determined as described above under ‘Chemical and microbiological characteristics of public market wastewater’.
The removal efficiencies by Scenedesmus sp. during the phycoremediation period were calculated according to the method used by Larsdotter et al. (2007).
Determination of removal rate of NH4– and PO43– and batch kinetic coefficient of Scenedesmus sp.











Statistical analysis
The data obtained with three determinations from the batch reactor systems of raw public market wastewater were subjected to linear regression analysis to find the coefficient of reduction (R2). The coefficients for removal of nutrients and reduction of pathogenic bacteria were considered significant at p < 0.05.
RESULTS AND DISCUSSION
Characteristics of public market wastewater
The characteristics of the public market wastewater collected from Ringgit public market centre at Parit Raja are illustrated in Table 2. It can be noted that the public market wastewater has high concentrations of nutrients in terms of NH4– (220.66 ± 10.03 mg L–1) and PO43– (67.31 ± 7.33 mg L–1). These findings are consistent with many reports in the literature (Zulkifli et al. 2012; Jais et al. 2015) which are due to blood residues that resulted from the washing of fish, chicken or meat. The high concentrations of nutrients are associated with high density of pathogenic bacteria that ranged from 8.841 ± 0.451 log10 CFU 100 mL–1 for E. faecalis to 10.32 ± 0.245 log10 CFU 100 mL–1 for S. aureus while E. coli was available in concentrations of 9.563 ± 0.327 log10 CFU 100 mL–1. These bacteria resulted from the wastewater generated from the washing of the public market floor and vegetables as well as chicken and fish products. Moreover, high levels of nutrients induced their growth. E. faecalis and E. coli are indicator bacteria that have high potential to survive in the environment (Al-Gheethi et al. 2013). S. aureus is used as an infectious agent indicator for microbiological hygiene of foods (Jin et al. 2013).
Characteristics of raw wet market wastewater collected from Ringgit public market centre at Parit Raja, Johor in the period between August 2015 to April 2016 (n = 7)
Parameters . | Unit . | Parameters concentrations . | Environmental quality Act 1974 (Regulation 2009) . | |
---|---|---|---|---|
Standards A . | Standards B . | |||
pH | 6.16 ± 0.121 | 6.0–9.0 | 5.5–9.0 | |
NH4− | mg L−1 | 220.66 ± 10.03 | 10 | 20 |
PO₄³− | mg L−1 | 67.31 ± 7.33 | 5 | 10 |
DO | mg L−1 | 2.44 ± 0.168 | NA | NA |
E. coli | Log10 CFU 100 mL−1 | 9.563 ± 0.327 | NA | NA |
E. faecalis | Log10 CFU 100 mL−1 | 8.841 ± 0.451 | NA | NA |
S. aureus | Log10 CFU 100 mL−1 | 10.32 ± 0.245 | NA | NA |
Parameters . | Unit . | Parameters concentrations . | Environmental quality Act 1974 (Regulation 2009) . | |
---|---|---|---|---|
Standards A . | Standards B . | |||
pH | 6.16 ± 0.121 | 6.0–9.0 | 5.5–9.0 | |
NH4− | mg L−1 | 220.66 ± 10.03 | 10 | 20 |
PO₄³− | mg L−1 | 67.31 ± 7.33 | 5 | 10 |
DO | mg L−1 | 2.44 ± 0.168 | NA | NA |
E. coli | Log10 CFU 100 mL−1 | 9.563 ± 0.327 | NA | NA |
E. faecalis | Log10 CFU 100 mL−1 | 8.841 ± 0.451 | NA | NA |
S. aureus | Log10 CFU 100 mL−1 | 10.32 ± 0.245 | NA | NA |
Ammonia (NH3), Orthophosphate (PO43–), Dissolved oxygen (DO); Standard A: Discharge upstream of water supply sources; Standards B: Discharge downstream of water supply sources. NA = Not available.
Response of pathogenic bacteria during the phycoremediation process and nutrient removal
Staphylococcus aureus concentrations during the aerated (A) and non-aerated (N) phycoremediation process of public market wastewater for 6 days and with different concentrations of Scenedesmus sp. (C1, 7 log10 cell 100 mL–1; C2, 8 log10 cell 100 mL–1; C3 9 log10 cell 100 mL–1); control (CB).
Staphylococcus aureus concentrations during the aerated (A) and non-aerated (N) phycoremediation process of public market wastewater for 6 days and with different concentrations of Scenedesmus sp. (C1, 7 log10 cell 100 mL–1; C2, 8 log10 cell 100 mL–1; C3 9 log10 cell 100 mL–1); control (CB).
E. coli concentrations during the aerated (A) and non-aerated (N) phycoremediation process of public market wastewater for 6 days and with different concentrations of Scenedesmus sp. (C1, 7 log10 cell 100 Ml–1; C2, 8 log10 cell 100 mL–1; C3 9 log10 cell 100 mL–1), control (CB).
E. coli concentrations during the aerated (A) and non-aerated (N) phycoremediation process of public market wastewater for 6 days and with different concentrations of Scenedesmus sp. (C1, 7 log10 cell 100 Ml–1; C2, 8 log10 cell 100 mL–1; C3 9 log10 cell 100 mL–1), control (CB).
E. faecalis concentrations during the aerated (A) and non-aerated (N) phycoremediation process of public market wastewater for 6 days and with different concentrations of Scenedesmus sp. (C1, 7 log10 cell 100 mL–1; C2, 8 log10 cell 100 mL–1; C3 9 log10 cell 100 mL–1).
E. faecalis concentrations during the aerated (A) and non-aerated (N) phycoremediation process of public market wastewater for 6 days and with different concentrations of Scenedesmus sp. (C1, 7 log10 cell 100 mL–1; C2, 8 log10 cell 100 mL–1; C3 9 log10 cell 100 mL–1).
The findings recorded in this study revealed that the presence of low concentrations of Scenedesmus sp. may prolong the survival period of pathogenic bacteria. However, they still have less competition potential in comparison to the algae. Cole (1982) reported that the bacterial cells have more activity in the presence of algae. This is because the algae provide the bacterial cells with vitamin B12 necessary for growth (Croft et al. 2005). Further, the phycoremediation process in the present work contributed significantly in the reduction of these pathogens due to the removal of nutrients by algae that enhanced the reduction of bacteria.
Scenedesmus sp. concentrations during the aerated (A) and non-aerated (N) phycoremediation process of public market wastewater for 6 days and with different concentrations of Scenedesmus sp. (C1, 7 log10 cell mL–1; C2, 8 log10 cell mL–1; C3 9 log10 cell mL–1).
Scenedesmus sp. concentrations during the aerated (A) and non-aerated (N) phycoremediation process of public market wastewater for 6 days and with different concentrations of Scenedesmus sp. (C1, 7 log10 cell mL–1; C2, 8 log10 cell mL–1; C3 9 log10 cell mL–1).
Based on the data obtained in the current work, it can be indicated that pathogenic bacteria may exhibit some survival in the presence of microalgae. However, they have no effect on Scenedesmus sp. growth in the public market wastewater. Nonetheless, the control experiments which were performed without microalgae inoculum achieved a high reduction of pathogenic bacteria. These findings are explained as a result of the sunlight effect where the absence of microalgae growth in the wastewater samples enhanced the penetration of sunlight and then inactivated the pathogenic bacterial cells. In contrast, in the presence of the microalgae growth layer, the penetration of sunlight may have been prevented and thus reduce the inactivation process. The inactivation of pathogenic bacteria by sunlight treatment has been mentioned in the literature (Al-Gheethi et al. 2015). Sunlight is one of the single most important disinfection factors of wastewater treated by the stabilization pond (Maynard et al. 1999). The efficiency of sunlight in the inactivation of pathogens is due to the solar UV-B, which is absorbed by the microorganism's DNA and has the ability to cause direct damage of the DNA structure by pyrimidine dimer formation (Jagger 1985). The second reason for the inactivation by sunlight is the absorption of shorter wavelength UV-A by cell constituents, including DNA (called endogenous photosensitisers). In the process, the activated constituents are reacted with the DO in the wastewater and generate high reactive photo-oxidised substances which lead to damage of the microorganism's DNA. The third reason may be related to the absorption of visible wavelengths in sunlight by extra-cellular constituents of the pond medium (exogenous photosensitisers notably humic material) (Al-Gheethi et al. 2015).
It was noted that the reduction of S. aureus, E. coli and E. fecalis in C2 (N) was less than that of C1 (N) and C3 (N); these findings could explain that the relationship between Scenedesmus sp. and pathogenic bacteria is dependent also on their concentrations in the wastewater and the conditions available in the wastewater medium such as the presence or absence of oxygen.
Furthermore, the results revealed that the wastewater needs to undergo a further disinfection process for the reduction of pathogenic bacteria. However, the storage of the wastewater generated from the phycoremediation process for 2 weeks may be sufficient for the reduction of pathogenic bacteria to less than detection limits. Al-Gheethi et al. (2017) indicated that the fecal indicator bacteria in the treated effluents has reduced to below the detection limits after 2 weeks of the storage period at room temperature. The storage system is used to regulate between the wastewater production and demand of treated effluents for irrigation or disposal (Barbagallo et al. 2003).
The removal of microalgae biomass generated in the phycoremediation of wastewater is conducted by several methods including flocculation processes (Atiku et al. 2016). Hauwa et al. (2017) investigated the harvesting of microalgae biomass generated during the phycoremediation of greywater by flocculation using Moringa oleifera seed flours and found that the harvesting efficiency was 86.80%.
Dissolved oxygen (DO) concentrations during the aerated (A) and non-aerated (N) phycoremediation process of public market wastewater for 6 days and with different concentrations of Scenedesmus sp. (C1, 7 log10 cell 100 mL–1; C2, 8 log10 cell 100 mL–1; C3 9 log10 cell 100 mL–1); control of bacteria (CB); control of algae (CA).
Dissolved oxygen (DO) concentrations during the aerated (A) and non-aerated (N) phycoremediation process of public market wastewater for 6 days and with different concentrations of Scenedesmus sp. (C1, 7 log10 cell 100 mL–1; C2, 8 log10 cell 100 mL–1; C3 9 log10 cell 100 mL–1); control of bacteria (CB); control of algae (CA).
pH values during the aerated (A) and non-aerated (N) phycoremediation process of public market wastewater for 6 days and with different concentrations of Scenedesmus sp. (C1, 7 log10 cell 100 mL–1; C2, 8 log10 cell 100 mL–1; C3 9 log10 cell 100 mL–1), control of bacteria (CB); control of algae (CA).
pH values during the aerated (A) and non-aerated (N) phycoremediation process of public market wastewater for 6 days and with different concentrations of Scenedesmus sp. (C1, 7 log10 cell 100 mL–1; C2, 8 log10 cell 100 mL–1; C3 9 log10 cell 100 mL–1), control of bacteria (CB); control of algae (CA).
Removal of ammonium (NH4−) during the aerated (A) and non-aerated (N) phycoremediation process of public market wastewater for 6 days and with different concentrations of Scenedesmus sp. (C1, 7 log10 cell 100 mL–1; C2, 8 log10 cell 100 mL–1; C3 9 log10 cell 100 mL–1); control of bacteria (CB); control of algae (CA).
Removal of ammonium (NH4−) during the aerated (A) and non-aerated (N) phycoremediation process of public market wastewater for 6 days and with different concentrations of Scenedesmus sp. (C1, 7 log10 cell 100 mL–1; C2, 8 log10 cell 100 mL–1; C3 9 log10 cell 100 mL–1); control of bacteria (CB); control of algae (CA).
Removal of orthophosphate (PO43–) during the aerated (A) and non-aerated (N) phycoremediation process of public market wastewater for 6 days and with different concentrations of Scenedesmus sp. (C1, 7 log10 cell 100 mL–1; C2, 8 log10 cell 100 mL–1; C3 9 log10 cell 100 mL–1); control of bacteria (CB); control of algae (CA).
Removal of orthophosphate (PO43–) during the aerated (A) and non-aerated (N) phycoremediation process of public market wastewater for 6 days and with different concentrations of Scenedesmus sp. (C1, 7 log10 cell 100 mL–1; C2, 8 log10 cell 100 mL–1; C3 9 log10 cell 100 mL–1); control of bacteria (CB); control of algae (CA).
Removal rate of NH4– and PO43– and batch kinetic coefficients of Scenedesmus sp.
(a) Effect of initial concentration of NH3 on the specific removal by Scenedesmus sp. with initial concentrations of 8 log10 cell mL–1. (b) Effect of initial concentration of PO43– on the specific removal by Scenedesmus sp. with initial concentrations of 8 log10 cell mL–1.
(a) Effect of initial concentration of NH3 on the specific removal by Scenedesmus sp. with initial concentrations of 8 log10 cell mL–1. (b) Effect of initial concentration of PO43– on the specific removal by Scenedesmus sp. with initial concentrations of 8 log10 cell mL–1.
(a) Determination of coefficient relationship between COD concentrations and Scenedesmus sp. specific growth rate. (b) Determination of coefficient relationship between BOD− concentrations and Scenedesmus sp. specific growth rate.
(a) Determination of coefficient relationship between COD concentrations and Scenedesmus sp. specific growth rate. (b) Determination of coefficient relationship between BOD− concentrations and Scenedesmus sp. specific growth rate.





(a) Effect of NH3 concentrations on specific removal rate by Scenedesmus sp. k = 4.82, km = 52. (b) Effect of PO43– concentrations on specific removal rate by Scenedesmus sp. k = 1.09, km = 85.56.
(a) Effect of NH3 concentrations on specific removal rate by Scenedesmus sp. k = 4.82, km = 52. (b) Effect of PO43– concentrations on specific removal rate by Scenedesmus sp. k = 1.09, km = 85.56.
The biokinetic model for removal of NH4– and PO43– by microalgae has been used by many authors in the literature. Biokinetic models are used to determine the potential rate and controlling steps necessary for designing a full scale biosorption process. Many kinetic models have been used to investigate the nutrient removal from various wastewaters. Moreover, the Michaelis–Menten model is used to determine the removal of nutrients. The Michaelis–Menten kinetic relationship is used to determine biokinetic coefficients such as k, reaction rate constant, Ks, half saturation constant, and Y, yield coefficient. The best algal substrate utilization was described more accurately and consistently with this logistic model than the Monod's model (Aslan & Kapdan 2006; Stringfellow et al. 2006).
CONCLUSIONS
The study aims to investigate the effects of pathogenic bacteria on the phycoremediation of wet market wastewater by Scenedesmus sp. The results revealed that the presence of pathogenic bacteria in the public market wastewater may create competition with microalgae in terms of NH4– removal due to the potential of bacteria in using NH4– as a nitrogen source. However, these concentrations are reduced by 3–4 log. The removal rate of NH4– and PO43– and batch kinetic coefficient of Scenedesmus sp. results revealed that the microalgae have high efficiency for removal of NH4– more than PO43–.
ACKNOWLEDGEMENTS
The authors are grateful for the financial support provided by the Fundamental Research Grant Scheme (FRGS) Vot 1453 from the Ministry of Education, Malaysia and Science Fund (02-01-13-SF0135).