Design of waste stabilization pond systems: A review

et al. 2019

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The design and execution of effective and informative experiments in comparative studies on water treatment is challenging due to their complexity and multidisciplinarity. Often, environmental engineers and researchers carefully set up their experiments based on literature information, available equipment and time, analytical methods and experimental operations. However, because of time constraints but mainly missing insight, they overlook the value of preliminary experiments, as well as statistical and modeling techniques in experimental design. In this paper, the crucial roles of these overlooked techniques are highlighted in a practical protocol with a focus on comparative studies on water treatment optimization. By integrating a detailed experimental design, lab experiment execution, and advanced data analysis, more relevant conclusions and recommendations are likely to be delivered, hence, we can maximize the outputs of these precious and numerous experiments. The protocol underlines the crucial role of three key steps, including preliminary study, predictive modeling, and statistical analysis, which are strongly recommended to avoid suboptimal designs and even the failure of experiments, leading to wasted resources and disappointing results. The applicability and relevance of this protocol is demonstrated in a case study comparing the performance of conventional activated sludge and waste stabilization ponds in a shock load scenario. From that, it is advised that in the experimental design, the aim is to make best possible use of the statistical and modeling tools but not lose sight of a scientific understanding of the water treatment processes and practical feasibility.

Section: Predictive Modelsmentioning

confidence: 99%

Section: Step 4: Preliminary Modelsmentioning

confidence: 99%

A Practical Protocol for the Experimental Design of Comparative Studies on Water Treatment

Thas

et al. 2019

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“…In fact, their average surface organic loadings were up to 250 and 185 kg·ha −1 ·day −1 , respectively, while the recommended limitations were 240 kg·ha −1 ·day −1 for WSPs at tropical and subtropical regions and only 200 kg·ha −1 ·day −1 for WSPs at altitudes above 2400 m a.s.l. [13,38]. These high loadings were associated with the sludge accumulation, which was also the reason of unavailable data at the bottom of location 1 and 2 in FPs.…”

Section: Spatiotemporal Influences On the Oxygen Dynamicmentioning

confidence: 99%

“…More importantly, numerous parameters applied in mechanistic models have been taken from different systems and model assumptions based on external characteristics might have to be applied. This approach of artificially assigning values to parameters can lead to biased results, which significantly deviates from real outputs [38]. Indeed, several simplifying assumptions along with geometric approximations caused the disagreements between computational fluid dynamics (CFD) model outputs and experimental results in the research of Alvarado, Sanchez, Durazno, Vesvikar and Nopens [39].…”

Section: Model Evaluationmentioning

confidence: 99%

A Closer Look on Spatiotemporal Variations of Dissolved Oxygen in Waste Stabilization Ponds Using Mixed Models

Pham

et al. 2018

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Dissolved oxygen is an essential controlling factor in the performance of facultative and maturation ponds since both take many advantages of algal photosynthetic oxygenation. The rate of this photosynthesis strongly depends on the time during the day and the location in a pond system, whose roles have been overlooked in previous guidelines of pond operation and maintenance (O&M). To elucidate these influences, a linear mixed effect model (LMM) was built on the data collected from three intensive sampling campaigns in a waste stabilization pond in Cuenca, Ecuador. Within two parallel lines of facultative and maturation ponds, nine locations were sampled at two depths in each pond. In general, the output of the mixed model indicated high spatial autocorrelations of data and wide spatiotemporal variations of the oxygen level among and within the ponds. Particularly, different ponds showed different patterns of oxygen dynamics, which were associated with many factors including flow behavior, sludge accumulation, algal distribution, influent fluctuation, and pond function. Moreover, a substantial temporal change in the oxygen level between day and night, from zero to above 20 mg O 2 ·L −1 , was observed. Algal photosynthetic activity appeared to be the main reason for these variations in the model, as it was facilitated by intensive solar radiation at high altitude. Since these diurnal and spatial patterns can supply a large amount of useful information on pond performance, insightful recommendations on dissolved oxygen (DO) monitoring and regulations were delivered. More importantly, as a mixed model showed high predictive performance, i.e., high goodness-of-fit (R 2 of 0.94), low values of mean absolute error, we recommended this advanced statistical technique as an effective tool for dealing with high autocorrelation of data in pond systems.

“…FPs and MPs were installed in plastic aquaria with dimensions 37 cm × 20 cm × 20 cm (L:W:H), resulting in a volume of 15 L and a HRT of almost five days. The dimensions of these ponds were calculated based on the standard guideline of pond design [15][16][17][18]. More specifically, the volumetric loading rate of the APs during the standard influent was maintained around 400 g BOD 5 •m −3…”

Section: Waste Stabilization Pondsmentioning

confidence: 99%

Statistically-Based Comparison of the Removal Efficiencies and Resilience Capacities between Conventional and Natural Wastewater Treatment Systems: A Peak Load Scenario

Charalambous

et al. 2018

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Emerging global threats, such as climate change, urbanization and water depletion, are driving forces for finding a feasible substitute for low cost-effective conventional activated sludge (AS) technology. On the other hand, given their low cost and easy operation, nature-based systems such as constructed wetlands (CWs) and waste stabilization ponds (WSPs) appear to be viable options. To examine these systems, a 210-day experiment with 31 days of peak load scenario was performed. Particularly, we conducted a deliberate strategy of experimentation, which includes applying a preliminary study, preliminary models, hypothetical tests and power analysis to compare their removal efficiencies and resilience capacities. In contrast to comparable high removal efficiencies of organic matter-around 90%-both natural systems showed moderate nutrient removal efficiencies, which inferred the necessity for further treatment to ensure their compliance with environmental standards. During the peak period, the pond treatment systems appeared to be the most robust as they indicated a higher strength to withstanding the organic matter and nitrogen shock load and were able to recover within a short period. However, high demand of land-2.5 times larger than that of AS-is a major concern of the applicability of WSPs despite their lower operation and maintenance (O&M) costs. It is also worth noting that initial efforts on systematic experimentation appeared to have an essential impact on ensuring statistically and practically meaningful results in this comparison study.