Page 209 - AJWEP-22-6

Performance of Kalobe waste ponds, Mbeya

2.4. WSP treatment efficiency evaluation are presented in the results section to visually support
The evaluation of treatment performance at Kalobe the stage-wise trends.
WSPs was conducted by analyzing the removal
efficiencies of six selected parameters (BOD, COD, 2.4.4. Pollutant load contribution
TSS, ammonia, nitrite, and TDS) across the three major Pollutant load (kg/day) for each parameter was computed
units: Anaerobic, facultative, and maturation ponds. using the standard mass loading equation (Equation I).
The contribution (%) of each industry to total
2.4.1. Efficiency calculation method pollutant loading was then derived by comparing each
The treatment efficiency for each parameter at each load to the total system load for BOD , COD, TSS,
5
stage was calculated using the conventional removal ammonia, nitrite, and TDS.
efficiency formula: This analysis enabled the identification of industries
that are primary contributors to organic, solids, and
cin-cout
Removalefficiency(%)= ×100 (II) nutrient loading, helping to pinpoint the most significant
cin sources of stress on the WSP system.

Where: 2.4.5. Application and relevance
• Cin = Influent concentration to the unit The findings from the contribution analysis are essential
• Cout = Effluent concentration from the unit for informing industrial pre-treatment compliance
This calculation was applied at two levels: (i) Stage- strategies, supporting load-based billing and regulatory
wise performance, covering the sequential treatment mechanisms, and prioritizing pollution control
units from anaerobic to facultative to maturation interventions.
ponds, and (ii) overall system performance, measured Results are presented in Section 3, alongside
from the inlet to the final effluent. The results were performance efficiency trends and compliance status.
expressed both as percentage removals and as mass load
reductions (kg/day), using flow-weighted calculations, 2.5. Compliance assessment
as described in Section 2.5. Compliance assessment was conducted to determine
whether the final effluent discharged from the Kalobe
2.4.2. Evaluation criteria WSPs meets the 2018 Tanzanian National Effluent
Performance was assessed against three benchmarks. Discharge Standards and other international guidelines,
First, compliance was evaluated relative to the Tanzania such as the 2006 World Health Organization (WHO)
National Environmental Standards (URT, 2007), recommendations for safe discharge and reuse. 19,14
which specify maximum final effluent limits of BOD ≤
30 mg/L, COD ≤ 60 mg/L, TSS ≤ 100 mg/L, NH –N ≤ 2.5.1. Standards used for compliance check
3
10 mg/L, NO –N ≤ 1 mg/L, and TDS ≤ 2,000 mg/L. For the Tanzanian National Standards, allowable
19
2
Second, results were compared to typical tropical WSP limits for key parameters include: BOD ≤ 30 mg/L,
5
performance ranges reported in the literature, where COD ≤ 60 mg/L, TSS ≤ 100 mg/L, NH –N ≤ 10 mg/L,
3
BOD removal is generally 70–90%, COD removal NO –N ≤ 1 mg/L, and TDS ≤ 2,000 mg/L. For WHO
2
60–80%, and TSS removal 60–90%, while nutrient guidelines, parameter limits vary depending on the
removals (ammonia and nitrite) tend to vary with intended reuse (e.g., unrestricted irrigation, restricted
temperature, algal activity, and hydraulic retention time irrigation, or discharge into surface waters). 19
(HRT). 7,20 Finally, the evaluation highlighted strengths
and limitations of the Kalobe system, with particular 2.5.2. Approach to compliance evaluation
emphasis on nutrient removal, which is often reduced Compliance evaluation was performed by comparing
in conventional WSPs that lack polishing units such as measured effluent concentrations from the final
constructed wetlands or sand filtration. 18 maturation pond with the specified standards. The
percentage of compliance for each parameter was
2.4.3. Data validation determined using the following formula:
All efficiency values were computed using the verified

dataset from field measurements and laboratory Compliance(%)=1 Exceedence ×100 (III)
analysis. Tabular summaries and graphical comparisons Standard

Volume 22 Issue 6 (2025) 203 doi: 10.36922/AJWEP025320249