Analysis of Algae and Bacteria Mixture in Removing Pollutants from Laundry Wastewater

Laundry detergents contain high nutrients, especially phosphate and nitrogen compounds. High concentrations of these nutrients can cause eutrophication to the water bodies and are toxic to aquatic organisms. Thus, this study aims to identify the characteristics of laundry wastewater and to enhance the treatment for the pollutants using algae and bacteria mixture. Moreover, the removal efficiency for this pollutant has been determined after the batch experiment. The characteristics of laundry wastewater were evaluated using in-situ and laboratory analysis. The in-situ testing included pH, temperature, and dissolved oxygen (DO) parameters. Laboratory experiments consist of biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), ammonia-nitrogen, nitrite-nitrogen, and nitrate-nitrogen. The results were recorded for the parameters before and after treatment. It can be revealed that the concentration of 2 g of algae had recorded 61% COD removal. For the concentration of 0.5 g algae, the highest percentage of removal recorded was 79.2% for ammonia-nitrogen. For total suspended solids (TSS), a maximum of 79% has been removed for a 0.5 g algae mixture. An average of 90% removal has been detected for 2 g algae and 1 g algae concentrations, respectively. Therefore, these algae and bacteria mixtures can be considered green technology to biodegrade the pollutants and enhance the quality of the laundry wastewater.


Introduction
Numerous causes can have a substantial effect which contributes to water pollution.The country's development is accelerating due to the high economic growth.As a result of development and industrialization, various changes have occurred.Therefore, the source of pollution is impacted by the debris coming from domestic, agricultural, and industrial sectors.There are also irresponsible human activities in dumping waste materials, thus polluting the water bodies.Some of this influence of water contamination can be seen immediately, while others take months or years to manifest.
Body waste (faeces and urine), hair shampoo, hair, food scraps, fat, laundry powder, fabric conditioners, toilet paper, chemicals, detergent, household cleansers, dirt, and microorganisms (germs) are just a few of the items that can deteriorate the humans and create harm to the environment [1].Due to the usage of detergents, domestic and industrial wastewater from sources including laundry and drycleaning businesses releases heavy concentrations of phosphates into the water systems [2].
In addition, phosphorus and nitrogen are nutrients that, if in excess, can cause eutrophication and brings toxicity to aquatic organisms.It can be denoted that combinations of algae and bacteria can remove pollutants, particularly from laundry wastewater.However, excessive plant growth in the water environment may reduce oxygen availability, changing habitats and endangering certain species.Therefore, phytoremediation, such as algae, must be balanced and coupled with bacteria culture to convey an effective treatment.Furthermore, wastewater bioremediation is becoming the most popular choice due to its long-term sustainability.This technique needs to be explored further to identify the performance of using bacteria culture with the enhancement of algae to remove pollutants in the wastewater.
This research focused on using an algae and bacteria mixture to degrade the pollutants in laundry wastewater.This method can be considered a green technology, with the results being more convincing due to the high percentage of removal obtained.Moreover, this study can provide details for the bioremediation technology in upgrading the existing system of the conventional wastewater treatment plant.

Collection of samples
Three litres of laundry wastewater samples were taken from the Taman Seri Sementa, Klang, Selangor, Malaysia household.The samples were taken from the outlet drain hose in a plastic bottle (3L), transported into the lab in an ice box, and tested chemically and physically within two hours [3].The sample of laundry wastewater was taken on November 7, 2022, and the inoculum of bacteria was collected from the wastewater effluent in Wastewater Treatment Plant (WWTP) UiTM Cawangan Dengkil.The inoculum sample was taken on November 3, 2022, and preserved in the refrigerator according to [3].The bacteria sample was collected using a bucket and then put into a bottle (10L).This inoculum is stored directly in a bottle and the refrigerator at the Environmental Laboratory, School of Civil Engineering, College of Engineering, UiTM Shah Alam.The inoculum contains a mixture of bacteria colonies coming from the wastewater effluent.The algae used in the study was Chlorella vulgaris and has been purchased from Sigma Aldrich & Co.

In-situ testing
The in-situ testing for pH, turbidity, and total dissolved solids (TDS) has been done using the HORIBA probe [4] for the effluent discharges of WWTP.In removing any potential contaminants at the probe and achieving an accurate testing value, this multi-parameter probe is cleaned with deionized water before the in-situ testing.

Laboratory testing
Laboratory tests have been conducted to determine the parameters such as biochemical oxygen demand (BOD), chemical oxygen demand (COD), ammonia-nitrogen (AN), total suspended solids (TSS), nitritenitrogen and nitrate-nitrogen.All laboratory tests refer to DR 2800 spectrophotometer [5].

Experimental setup
The samples of laundry wastewater with an amount of 200 ml each were inserted in three flasks, respectively.Each flask also contained 50 ml of inoculum of bacteria with a total of 250 ml and the laundry wastewater.One more flask has been inserted with laundry wastewater only and is considered the control sample.
The Chlorella vulgaris powder was weighed with concentrations of 0.5 g, 1 g, and 2 g.The mixture ratio of algae and bacteria used in this experiment were 0.5:50, 1:50, and 2:50.This concentration has been used based on another study [6] with some modifications.Aeration has been supplied to the flasks to enhance the aerobic process of bacteria.The powder was then added to the three flasks that contained laundry wastewater and bacteria inoculum.
The duration of this batch experiment was within one week (7 days).The initial and daily readings have been taken to evaluate the removal performance of the algae ad bacteria mixture.Figure 1 shows the experimental setup of the batch experiment.

The Characteristics of Laundry Wastewater Before Treatment
Based on Table 1, laundry wastewater is acidic as the pH reading value is approximately 5.74.However, the value of BOD is low (15.45 mg/L).On the other hand, the concentration of COD is very high, with an amount of 216 mg/L.Substantially, the accumulation of ammonia-nitrogen, TSS, nitrite-nitrogen and nitrate-nitrogen were minimal, with values of 1.29 mg/L, 48 mg/L, 0.001 mg/L and 0.119 mg/L, respectively.Therefore, from the characteristics of the laundry wastewater, further treatment is needed before the effluent is discharged to the water bodies.

Removal efficiency of treated Laundry Wastewater
After seven days, the concentrations of 1 g and 2 g of algae obtained the highest percentage of removal for COD, which was recorded at 58% and 60%.According to [7], bacteria can break down organic compounds into smaller molecules, such as nutrients, so that algae can absorb them.Later, the removal percentage for ammonia-nitrogen and TSS were 71% and 77.4% for the concentration of 0.5 g at the end of the experiment.For a 2 g concentration of C. vulgaris and a bacteria mixture, the maximum percentage of nitrate-nitrogen removal was 99%.Ammonia-nitrogen has been extant in the initial laundry wastewater samples.The functioning nitrifying bacteria consumed a substantial amount of ammonia-nitrogen in the laundry wastewater [8].In the analysis, laundry wastewater with a 1 g concentration of algae has an unsurpassed rate of nitritenitrogen removal (96% of nitrite-nitrogen was successfully removed).As nitrification occurs in the experiment, the nitrifying bacteria accumulate ammonia-nitrogen and convert it to nitrite-nitrogen.Later, with sufficient oxygen supply, nitrite-nitrogen will be transformed into nitrate-nitrogen in a twostep nitrification process [9].
Consecutively, in the presence of organic matter, the denitrifying bacteria would absorb nitratenitrogen under facultative (semi-aerobic) conditions, which initially causes a decrease in nitrate-nitrogen and promotes bacterial growth.From the observation, a significant percentage of removal has been evaluated after the treatment using the algae and bacteria mixture.It can be highlighted that algae can consume nitrogen and further reduce the pollutants in laundry wastewater.Together with a colony of bacteria from the inoculum, more pollutants can be degraded and further enhance the quality of the effluent.

Conclusion
Algae and bacteria mixture can be used as a medium to remove pollutants from laundry wastewater due to the results evaluated from the experiment.From the batch experiment, Chlorella vulgaris of 2 g concentration combined with bacteria mixture can potentially remove the high amount of pollutants.It can be observed by the maximum removal percentage obtained for COD and nitrate-nitrogen.Based on the study conducted, pollutant removal decreases on the seventh day; if the study period exceeds seven days, there is a possibility of more reduction in the pollutant's concentration.Moreover, bioremediation treatment can be reckoned as a cost-effective method for treating laundry wastewater, as algae and bacteria cultures are considered regenerative resources that can adjust to the complex environment.

Figure 2 .
Figure 2. A) Removal efficiency of COD using C. vulgaris and Bacteria mixture; B) Removal efficiency of Ammonia-nitrogen using C. vulgaris and Bacteria mixture.

Figure 3 .
Figure 3. A) Removal efficiency of TSS using C. vulgaris and Bacteria mixture; B) Removal efficiency of Nitrite-nitrogen using C. vulgaris and Bacteria mixture.

Figure 4 .
Figure 4. Removal efficiency of Nitrate-nitrogen using C. vulgaris and Bacteria mixture.

Table 1 .
Characteristics of laundry wastewater before treatment