Environmental Engineering
S. Mokatip; K. Chunkao; W. Wararam; S. Bualert; O. Phewnil; T. Pattamapitoon; N. Semvimol; P. Maskulrath; P. Rollap; S. Thaipakdee
Abstract
BACKGROUND AND OBJECTIVES: Domestic wastewater pollution in Thailand presents challenges due to limited space and a high concentration of point source effluents. This phenomenon often leads to domestic wastewater exceeding the capacity of local treatment systems. This study aims to expand the knowledge ...
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BACKGROUND AND OBJECTIVES: Domestic wastewater pollution in Thailand presents challenges due to limited space and a high concentration of point source effluents. This phenomenon often leads to domestic wastewater exceeding the capacity of local treatment systems. This study aims to expand the knowledge gained from The King’s Royally Initiated Laem Phak Bia Environmental Research and Development Project by evaluating the treatability of municipal wastewater. It utilizes a constructed wetland system in conjunction with a transfer and point source system. After the implementation of this primary system, the reduction in highly contaminated domestic wastewater could enhance the treatment loading of other secondary treatment systems or even facilitate its release into natural pathways.METHODS: In the sampling collection process, the dynamics of the collection points were categorized into three different zones: 1) the point sources of domestic wastewater within a municipality, where 15 sample points were selected to represent the municipality; 2) the collection pond within the municipality and the transfer pipeline, comprising three collection points of the system; 3) the constructed wetland treatment system, where five water samples were collected in relation to the length of the existing 100-meter plot. The water samples were collected using four 1-liter polyethylene bottles. The analysis parameters were the biological oxygen demand, total nitrogen, nitrate, total phosphorous and phosphate, and other parameters related to domestic wastewater treatment efficacy.FINDING: This study reveals that the domestic wastewater in Phetchaburi Province initially has a high organic content, leading to a biochemical oxygen demand: nitrogen: phosphorous ratio of 100:2.5:0.2 favoring anaerobic degradation. This ratio shifts in the constructed wetland system, located 18.5 kilometers away, to 100:10.5:2.3, promoting anaerobic treatment. The system shows high efficacy, with 81.4, 50.0, and 58.3 percent removal rates for biochemical oxygen demand, nitrogen, and phosphorus, respectively. This efficacy corresponds to a notable reduction in average biochemical oxygen demand from 740.0 to 9.7 milligrams per liter. Moreover, changes are observed in total nitrogen content, shifting from 20.8 to 2.8 milligrams per liter, in the system’s effluent. While lastly, the total phosphorous decreased from 2.75 to 0.60 milligrams per literCONCLUSION: This treatment method can be effectively applied to small-scale constructed wetland systems within households. The recommended hydraulic retention time is between 29 and 60 hours under anaerobic conditions and 3 days under aerobic conditions. The changes in the composition of municipal wastewater, which is highly organic, support the use of both degradation processes. The knowledge and application of the constructed wetland system could be suggested for the primary treatment system of domestic wastewater within municipalities, given that this system would provide support to the central wastewater treatment system for enhanced efficacy.
Environmental Engineering
C. Tudsanaton; T. Pattamapitoon; O. Phewnil; W. Wararam; K. Chunkao; P. Maskulrath; M. Srichomphu
Abstract
BACKGROUND AND OBJECTIVES: Community domestic wastewater contains organic substances that can be decomposed through natural processes. Treatment using oxidation pond systems is popular in tropical zones because these locations provide a climate suitable for the growth and organic decomposition activities ...
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BACKGROUND AND OBJECTIVES: Community domestic wastewater contains organic substances that can be decomposed through natural processes. Treatment using oxidation pond systems is popular in tropical zones because these locations provide a climate suitable for the growth and organic decomposition activities of various bacteria that remove organic contaminants from wastewater. Given that bacteria play an important role in the biodegradation of organic substances in wastewater treatment plants, their degradation activity is used as an indicator of water quality. The purpose of this study is to examine the vertical variability of bacteria in natural treatment oxidation ponds in tropical zones.METHODS: Wastewater samples were collected from an oxidation pond at 3 different depths (0–0.6, 0.6–1.5 and more than 1.5 meter), and their chemical, physical and biological qualities were analysed. Next-generation sequencing techniques were used to identify bacterial diversity, and the water quality at each depth was applied as an indicator of bacterial degradation activities.FINDINGS: Community domestic wastewater contained 10 major bacterial phyla that differed at different depths. Amongst these phyla, the Actinobacteriota dominated (25.35 to 28.23 percent), followed by Cyanobacteria (19.49 to 21.57percent), Planctomycetota (15.50 to 17.41 percent), Firmicutes (9.97 to 10.79 percent), Proteobacteria (9.73 to 10.79 percent), Verrucomicrobiota (6.47 to 7.69 percent), Chloroflexi (2.79 to 2.99 percent), Bacteriota (0.96 to 1.41 percent), Acidobacteriota (0.70 to 0.80 percent) and SAR324 clade (marine group B) (0.69 to 0.61 percent). Four organic substances were found in contaminated domestic wastewater. 1) Photosynthetic cyanobacteria and phytoplankton performed aerobic degradation and accounted for the dissolved oxygen levels of 7.76, 7.45 and 7.42 milligrams per liter, respectively at various depths along the vertical profile. 2) Bacteria and archaeans that participate in carbon compound treatment included Planctomycetes, Verrucomicrobiota, Bacteroidota and Euryarcheota. These bacteria exhibited a treatment efficiency for biochemical oxygen demand and low abundance at all depths. Biological oxygen demand increased to 23.11, 24.27 and 34.48 milligrams per liter with depth. 3) Nitrogen-cycling bacteria included nitrifying and denitrifying bacteria. They belonged to the Actinobacteriota, Planctomycetota, Firmicutes, Verrucomicrobiota, Chloroflexi, Bacteriota, Protrobacteria and Acidobacteriota phyla. They exhibited an ammonia-nitrogen treatment efficiency of 91.73 percent. 4) Phosphorus cycling–related bacteria in the Actinobacteriota phylum presented the orthophosphorus treatment efficiency of 65.41 percent.CONCLUSION: The results of this study suggested that bacterial communities did not significantly differ along oxidation depth because they work together with chemotrophs, which participate in organic substance decomposition, and phototrophs, which are involved in oxygen generation and nutrient removal. All of the bacteria found in domestic wastewater benefit and support oxidation pond systems in tropical zones. Anaerobic bacteria can be found in wastewater and used in treatment systems due to their protective mechanisms against oxygen toxicity and self-repair mechanisms. The knowledge gained from this study can be used as a reference in future works on natural wastewater treatment systems.
