The Effect Of Light-Emitting Diodes (LEDs) Light Intensity on High Rate Algal Reactor System In Laundry Wastewater Treatment
Adhi Triatmojo a, *, Bieby Voijant Tangahu a
a Department of Environmental Engineering, Institut Teknologi Sepuluh Nopember, Indonesia
* Corresponding author.
E-mail address:
ABSTRACT
Laundry wastewater contain nutrients with high concentration. Nutrients commonly found in laundry wastewater are nitrogen and phosphorus. One of the technology for wastewater processing with high nutrient content is by using High Rate Algal Pond (HRAP). This study has a purpose to determine the effect of duration and intensity of light for the removal of Chemical Oxygen Demand, Nitrogen-ammonia, and Phosphate content.
This study was conducted to assess the exposure of light that has greater efficiency for nutrient removal in laundry wastewater in the HRAP system. The microalgae used is Chlorella Vulgaris that can grow in polluted environments and suitable for use in wastewater processing. Variable that being used light intensity of 2000-3000 Lux, 4000-5000 Lux, and 6000-7000 Lux to determine the most efficient intensity in nutrient removal. Parameters to be tested in this study were Chemical Oxygen Demand, Nitrogen-ammonia, Phosphate to determine the efficiency of nutrient removal and Chlorophyll α to determine the conditions of Microalgae development.
The results showed that the greatest ability for nutrient removal was the reactor duration of 24 hours light exposure with light intensity 6000-7000 Lux is able to remove 54.63% of Chemical Oxygen Demand, 41.60% of Nitrogen-Ammonia and 15.16% of Phosphate. Based on the result of statistic test, the variable of light intensity significantly influence the removal efficiency of Chemical Oxygen Demand and Nitrogen-Ammonia shown With P-value value <5%.
Keywords: High Rate Algal Pond, Laundry Wastewater, Light Intensity, Light-Emitting Diodes, Microalgae.
1. Introduction
As the population increases, the wastewater generated by human activities is increasing, environmental pollution by liquid waste in Indonesia resulted in the decrease of river water body water quality. According to BLH [2] the water quality decline is caused by domestic waste that contribute to contamination by 60% and industrial waste by 40%. Tectona found that [11] laundry business is one of the businesses that require clean water and produce a lot of wastewater, so if the wastewater is not processed first it can lead to eutrophication and explosion of algae. On similar research Ciabatti [4] resulted in water needs for laundry industry average 15 Liter / kg laundry clothes, average laundry industry per day wash 25 kg of clothes so as to produce waste water about 400 Liter / day. Laundry waste is one of the causes of algae blooming in water bodies because it has high organic content and nutrient concentrations that can support the growth of microalgae.
One of the urban wastewater treatment systems using algae usually aims to reduce the levels of nutrients. The development and application of a processing system capable of lowering the levels of organic substances as well as nitrogen such as High Rate Algal Pond is very important to ensure the maintenance of water bodies quality according to Garcia et., al. [5]. The assimilation of N by algae and floating aquatic plants accounted for about 65% of total N decrease, ammonia volatilization of 15% and about 20% total decrease in N content can be assumed based on nitrification-denitrification process concluded by Mostret et al., [10]. In 2010, Wang's [13] research on the utilization of mixed algae for domestic wastewater treatment and biodiesel feedstock, from the research obtained the efficiency of allowance N of 92-95% and P by 62-80%. HRAP is one of the treatment that can be applied in Indonesia to reduce laundry wastewater nutrient. HRAP has an advantage over procurement, operational and maintenance costs that are relatively cheaper and easier than other methods from Garcia [5]. According to Wang's [13] research specific use of algae may allow for greater nutrient removal, in addition to specific species biomass byproducts for various purposes. In research about usage of microalgae Man [8] suggested that Chlorella Sp. is a type of algae that has tolerance levels of pollutants are quite good and easy to obtain, so Chlorella Sp. is often used in wastewater treatment.
This study tested the decrease of nutrient content in polluted water waste waste by using High Rate Algal Reactor (HRAR), with variation of light intensity to know the efficiency of decrease of nutrient content, and the development of alga yielded. HRAR are performed at detention time of 6 days with variation of light intensity 2000-3000 Lux, 4000-5000 Lux, and 6000-7000 Lux. Removal efficiency of each reactor will be analyzed ability in decreasing parameters of COD, nitrogen-ammonia, and phosphate, Chlorophyll α will be analyzed to comprehend the microalgae development. In Photobioreactor the growth of microalgae will be equal as the light intensity, using fluorescent lamp light intensity compatible are 2000 Lux till 12000 Lux Masaki et al., 2015 [8]. Using Light Intensity from LEDS lamp for microalgae above 7000 Lux can resulted in photoinhibition, where microalgae growth will be inhibited Ifeanyi [6].
2. Materials and methods
2.1. Collection of Sample
At the beginning of the research, laundry wastewater are analyzed with COD, Ammonia, and Phosphate as the parameters. Sampling is done in Keputih District Sukolilo with Integrated Sample method on 4 Different Laundry Enterprises. The results showed that COD and phosphate values were ranged between 600-829 mg/L and 8,53-12,62 mg/L.
2.2. Materials and Medium
This experiment uses 6 reactor containers consisting of 3 test reactor containers and 3 containers of control reactors, the volume of reactor that being used is ± 12 Liter with dimension of diameter 30 cm and 27 cm height. Lighting sources used are the Light Emitting Diodes 18 watt Phillips Brand, the light intensity are measured using the Lux Meter HS1010 on the surface of the reactor. The algae used in this study was Chlorella vulgaris previously filtered with a 50 μ cloth filter, the use of cloth filter to harvest microalgae has an efficiency of 94 ± 2% Bejor [1].
2.3. Determination of The Effect of Light Intensity on High Rate Algal Reactor
Nitrogen-Ammonia was analyzed by using Nesslerization Method by means of absorbance readings using spectrophotometer. Phosphate in orthophosphate form was analyzed using 4500-P Stannous Chloride Methode method using Ammonium Molybdate and absorbance readings using a spectrophotometer. COD (Chemical Oxygen Demand) analysis was performed by using the close reflux method and FAS (Ferrous Amommonium Sulfate) solution to determine the COD content found in the reactor.
Chlorella Vulgaris was illuminated by Light Emitting Diodes with variety of light intensity 2000-3000 Lux, 4000-5000 Lux, and 6000-7000 Lux. The reactor detention time is 6 days with constant agitation. Removal efficiency of each reactor will be analyzed through the removal parameters of COD, nitrogen-ammonia, and phosphate. Chlorophyll α will be analyzed to comprehend the microalgae development.
3. Results and discussion
3.1. Nitrogen-Ammonia Removal
The light intensity experiment showed that 6000-7000 Lux was adequate for algal growth. This observation was in line with the report of Ifeanyi et. al. [6] who reported that light with higher intensity can boost the growth of algae. The growth of algae in reactor can affect HRAR (High Rate Algal Reactor) nutrient removal efficiency Lilliana [7], the higher light intensity can make microalgae concentration higher, so the better removal efficiency will become. The rate of Ammonia removal in all batch reactor increased at higher light intensity as can be seen on Figure 1 and Figure 2. A linear correlation between chlorophyll α and ammonia concentration in the reactor was observed for the experiments. It is suggested that the ammonia are consumed by microalgae.
Fig 1. HRAR Ammonia Trend
Fig 2. HRAR Ammonia Removal
It is seen that the ammonia content range always decreases, but on day 3 and 4 ammonia returns up, after that the trend on the next day continues to fall. This is due to the 3rd and 4th days some of the microalgae present in the reactor begin to die and decompose thus releasing the nitrogen back into the reactor. The optimum removal efficiency is in the reactor with 6000-7000 Lux lighting which is 50%, while the 4000-5000 Lux and 2000-3000 Lux reactors have 32% and 26% removal efficiency. The control reactor has a lower efficiency than the reactor containing the microalgae. The range of removal at the control reactor ranged from 21-39%, while the reactor containing microalgae of N-ammonia removal ranged from 58-73%. This suggests that the uptake of microalgae greatly affects the N-ammonia removal process, because in general ammonia is the easiest nitrogen source to uptake by microalgae Garcia [4].
3.2. HRAR Phosphate Removal
When correlating the removal percentage of phosphate with light intensity, the correlation coefficients were low as we can see at Figure 3 and Figure 4. This suggested that factors other than uptake from microalgae can be at play. The mechanism that plays an important role in the reduction of phosphate concentration is immobilization in the sediment with the precipitation of phosphorus-calcium and uptake bonds by microalgae Chen [3] .
Fig 3. HRAR Phosphate Trend
Fig 4. HRAR Phosphate Removal
Figure 3 shows that the overall phosphate concentration is decreasing. The phosphate concentration in the reactor tends to fluctuate, it could be because the microalgae in the reactor metabolize so as to express the waste Vymazal [12]. Then in Figure 4 can be seen the efficiency of removal from 24-hour lighting reactor. Reactor with intensity 4000-5000 has a provision of 30%, while 6000-7000 Lux has a percentage that is not much different that is 27%. Reactor with intensity 2000-3000 has the lowest percentage of allowance that is 7%. On the graph it is seen that the removal efficiency at the control reactor has the greatest allowance efficiency of 19-36%. The phosphate removal agent is smaller when compared to N-ammonia, that is because according to the redfield ratio the C: N: P requirement for microalgae growth is 106: 16: 1 thus uptake phosphate by microalgae will be smaller.
3.3. HRAR Phosphate Removal
Correlation between Chemical Oxygen Demand and light intensity are linear as shown in Figure 5 and Figure 6. In the reactor 2000-3000 Lux trend of COD concentration continues to decline and tend to be stable until the end of residence time, In the reactor 4000-5000 Lux and 6000-7000 Lux concentration increase occurred on day 2 and to 3. Fluctuations in concentration occurs due to dead microalgae will decompose And counted as organic substances dissolved in wastewater.
Fig 5. HRAR Chemical Oxygen Demand Trend
Fig 6. HRAR Chemical Oxygen Demand Removal
Figure 6 shows that sequentially the 6000-7000 Lux, 4000-5000 Lux, and 2000-3000 Lux reactors have 42%, 37%, and 35% removal percentages respectively. The greater the intensity of light, the greater the percentage of COD removal. This is due to the amount of light intensity that affects the amount of microalgae requiring organic substances to breed.
4. Conclusions
The intensity of light has a significant effect on the removal of Ammonia and Chemical Oxygen Demand. It is proved by ANOVA statistic test that has P value <5%, light intensity is proportional to percent nutrient removal. Phosphate is not significantly affected by light intensity, this result is proved by ANOVA statistic test which shows P-value> 5%. The largest removal percentage for COD is 55%, and Ammonia is 46% with light intensity of 6000-7000 Lux, whilst phosphate has 30% with light intensity of 4000-5000 Lux. In this work, the effects of light intensity on dissolved ammonia, phospate, and chemical oxygen demand removal, microalgal growth were studied. From the knowledge obtained, this algal species can be improved for field trial possibly for bioremediation purpose.
Acknowledgement(s)
The authors are grateful to the LPPM ITS institution for their financial support. In addition we are grateful to the Environmental Engineering FTSLK ITS for their technical cooperation and provision of chemical compounds.
References
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