The research examines effluent trends from 2021 to 2024 and tests a mini constructed wetland using water hyacinth (Eichhornia crassipes) as a polishing unit. The results provide rare long-term operational evidence from a school-scale WWTP, linking regulatory compliance with ecological reliability.
Why School Wastewater Deserves Attention
Wastewater management remains a global sustainability issue. Educational institutions, especially vocational chemical schools, produce laboratory wastewater that is low in volume but high in pollutant concentration. Such wastewater may contain ammonia, dissolved organic compounds, and heavy metals.
These characteristics create operational risks. Sudden laboratory discharges can cause extreme pH shifts. When pH drops too low or rises too high, biological treatment processes become unstable. Microorganisms responsible for breaking down pollutants can lose efficiency, particularly in removing ammonia.
For schools operating compact WWTP systems, long-term monitoring is critical. Meeting regulatory standards in average conditions does not automatically guarantee ecological safety under variable loads.
How the Study Was Conducted
Desrita Gevia and her colleagues applied a quantitative descriptive–evaluative approach. The research combined:
- Semester-based effluent monitoring data from 2021–2024
- A snapshot influent–effluent measurement in October 2025
- An experimental mini wetland polishing test
Parameters analyzed included:
- pH
- Biological Oxygen Demand (BOD)
- Chemical Oxygen Demand (COD)
- Ammonia (NH3-N)
- Heavy metals (Pb, Cd, Cr, Mn, Zn, Fe, Cu)
The mini wetland system used a 13-liter container filled with 10 water hyacinth clumps. Wastewater was retained for approximately eight days. Researchers measured pH on day 0, day 4, and day 8, and compared pollutant concentrations before and after treatment.
The team calculated removal efficiency and compared multi-year effluent data against Indonesia’s national wastewater standard under Minister of Environment Regulation No. 5 of 2014.
Key Findings from 2021–2024 Monitoring
The four-year dataset shows strong performance in organic pollutant control:
- COD consistently remained below the national limit of 100 mg/L.
- BOD consistently remained below the limit of 50 mg/L.
- Organic removal efficiency reached 98.9% for BOD and 90.4% for COD in snapshot testing.
However, pH instability emerged as a critical weakness:
- Effluent pH dropped to 4.15 in the first semester of 2023.
- The acceptable regulatory range is 6–9.
Ammonia removal was moderate rather than optimal:
- Snapshot ammonia removal efficiency reached 47.1%.
- Acidic influent conditions likely reduced nitrification performance.
Heavy metals generally complied with regulatory thresholds. Iron (Fe) and copper (Cu) were effectively reduced, but fluctuations were observed across semesters.
The study concludes that the WWTP reliably controls organic pollution but remains vulnerable to episodic laboratory discharges that alter pH.
Performance of the Mini Water Hyacinth Wetland
The experimental polishing unit produced mixed results.
Positive outcomes:
- pH increased from 5.4 to 6.7 within eight days, moving toward neutrality.
- Total iron removal reached 95% after combined treatment.
- Copper removal reached 92% after combined treatment.
Negative outcomes:
- COD increased after wetland treatment.
- Ammonia concentrations rose in the wetland outlet.
- Manganese (Mn) and zinc (Zn) also showed increases.
The wetland improved pH stabilization and enhanced removal of certain metals. However, it introduced new challenges for organic matter and nitrogen control.
According to Desrita Gevia of Universitas UPGRISBA, the findings show that “polishing performance is parameter-specific and highly dependent on design.” She explains that plant biomass and root exudates may release additional organic compounds, while limited dissolved oxygen can suppress nitrification, leading to ammonia increases.
Why COD and Ammonia Increased
Constructed wetlands rely on plant uptake, microbial activity, sedimentation, and adsorption. Water hyacinth supports phytoremediation by absorbing metals and facilitating rhizosphere processes.
However, without sufficient aeration and biomass management:
- Decomposing plant matter can add organic load.
- Nitrogen mineralization can elevate ammonia.
- Low oxygen conditions inhibit nitrifying bacteria.
The study shows that natural systems require engineering optimization. Wetlands cannot rely on vegetation alone. Media selection, aeration, hydraulic retention time, and routine harvesting are critical.
Implications for Schools and Policymakers
This research provides practical insights for school administrators, environmental engineers, and regulators:
- Regulatory compliance does not guarantee system stability.
- pH equalization is essential in laboratory wastewater treatment.
- Small-scale WWTPs need continuous monitoring to detect episodic shocks.
- Constructed wetlands can enhance metal removal but require proper design.
For policymakers, the findings support stricter operational guidance for educational institutions with laboratory facilities. For schools, the study highlights the importance of preventive design rather than reactive correction.
Strengthening pH control upstream of biological treatment and improving aeration could significantly enhance ammonia removal. Hybrid wetland systems with staged aerobic–anoxic zones may offer better long-term performance.
Author Profiles
Together, Desrita Gevia, Erismar Amri, and Nefilinda contribute applied research addressing real-world environmental challenges in educational institutions.
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