Dimensionality Reduction Analysis of the Integrated Solar and Hydraulic Jump Enhanced Waste Stabilization Pond Model Parameters

The study investigated the structure of the integrated solar and hydraulic jump enhanced waste stabilization pond (ISHJEWSP) variables. Also, to determine the cluster of the most important variables that account for the performance of the ISHJEWSP using principal component analysis (PCA). Three sets of experimental ponds were constructed with varying locations of point of initiation of hydraulic jump. Wastewater samples collected from the inlet and outlet for varying inlet velocities were examined for physicochemical and bacteriological characteristics for a period of nine months. The Pearson’s R-matrix and KMO statistic were used in evaluating the structure of the variables. Consequently, the variables of temperature, pH, algae concentration, solar radiation, and locations of the point of initiation of hydraulic jump were subjected to PCA. Two components had eigenvalues above the Jolliffe’s criterion and in combination explained 90.66% of the total variance. The inflexion of the scree plot justified the retained components. The analysis after rotation revealed that the parameters of pH, temperature, solar radiation, and algal concentration loaded highly to component 1. This underscores the precedence of ambient climatic conditions, alongside the state of the wastewater in general, to the inlet velocity and location of point of initiation of hydraulic jump.

Improving the performance of waste stabilization ponds in an arid climate

In many parts of the world, waste stabilization ponds (WSPs) are currently the preferred wastewater treatment method for municipal wastewater. The objective of this research is to examine the performance of a WSP in an arid climate region and to identify ways to improve its purification efficiency so that it can meet the criteria for reuse. The results attributed the poor performance to both improper process and physical design after 12 months of physicochemical and bacteriological analyses, as well as monitoring of operation, maintenance and loading rates. In tertiary treatment, maturation ponds are added, an increase in the capacity of the station, and management of the flow rate and retention time for each pond. By simulating the new WSP with GPS-X, the best pond area ratio obtained is 2.5 m2/capita, with a retention time of 4 days for anaerobic ponds, 20 days for facultative ponds and 3 days for two maturation ponds in series, which is suitable and provides reduction rates of BOD and fecal coliforms of 95 and 99%, respectively, with an average effluent concentration of 20 mg/L and 195 CFU. According to the results, well-maintained WSPs provide a viable, self-sufficient and environmentally friendly wastewater treatment solution for irrigation water supply in dry areas.

Agricultural Waste and Wastewater as Feedstock for Bioelectricity Generation Using Microbial Fuel Cells: Recent Advances

In recent years, there has been a significant accumulation of waste in the environment, and it is expected that this accumulation may increase in the years to come. Waste disposal has massive effects on the environment and can cause serious environmental problems. Thus, the development of a waste treatment system is of major importance. Agro-industrial wastewater and waste residues are mainly rich in organic substances, lignocellulose, hemicellulose, lignin, and they have a relatively high amount of energy. As a result, an effective agro-waste treatment system has several benefits, including energy recovery and waste stabilization. To reduce the impact of the consumption of fossil energy sources on our planet, the exploitation of renewable sources has been relaunched. All over the world, efforts have been made to recover energy from agricultural waste, considering global energy security as the final goal. To attain this objective, several technologies and recovery methods have been developed in recent years. The microbial fuel cell (MFC) is one of them. This review describes the power generation using various types of agro-industrial wastewaters and agricultural residues utilizing MFC. It also highlights the techno-economics and lifecycle assessment of MFC, its commercialization, along with challenges.

Microalga-Mediated Tertiary Treatment of Municipal Wastewater: Removal of Nutrients and Pathogens

The microalgal strain Chlorella sorokiniana isolated from a waste stabilization pond was used for tertiary treatment of municipal wastewater. Three light:dark (L:D) regimes of 12:12, 16:8, and 24:0 were used for treating wastewater in microalga (A), microalga + sludge (A + S), and sludge (S) reactors. The removal of nutrients (N and P) was found to be the highest in the microalga-based reactor, with more than 80% removal of biochemical oxygen demand (BOD) and 1.2–5.6 log unit removal of pathogens. The addition of sludge improved chemical oxygen demand (COD) removal. Nitrifiers were found to be predominant in the A + S reactor. Algal biomass productivity was more than 280 mg/L/d in all the L:D regimes. The increase in light regime improved nutrient removal and biomass productivity in the algal reactor. Results of the kinetic study showed that (i) nitrifiers had more affinity for ammonium than microalga, and hence, most of the ammonia was oxidized to nitrate, (ii) microalga assimilated nitrate as the primary nitrogen source in the A + S reactor, and (iii) solubilization of particulate organic nitrogen originated from dead cells reduced the nitrogen removal efficiency. However, in the microalga-based reactor, the ammonium uptake was higher than nitrate uptake. Among pathogens, the removal of Salmonella and Shigella was better in the A + S reactor than in the other two reactors (microalga and sludge reactor). Additionally, the heterotrophic plate count was drastically reduced in the presence of microalga. No such drastic reduction was observed in the stand-alone sludge reactor. Kinetic modeling revealed that microalga–pathogen competition and pH-induced die-off were the two predominant factors for pathogen inactivation.

Upgrading of waste stabilization ponds using a low-cost small-scale fine bubble diffused aeration system

Waste Stabilization Ponds (WSPs) are known for the economical treatment of wastewater, especially if low-cost land is available. In this research to overcome some common operational problems such as undesirable color changes in ponds, severe odor problems, and most importantly, deviations from the effluent standards, the performance of a novel installation of a small-scale fine bubble diffused aeration system in the inlet zone of the facultative pond has been investigated. The long-term operational data of the system in two wastewater treatment plants in the east of Iran demonstrated that this system can significantly improve the efficiency of the treatment plant in addition to eliminating the mentioned operational problems. Pre-aeration of the inlet zone of the facultative ponds (Birjand WSPs) by the aeration system consists of 250 fine bubble disk diffusers (12 inches in diameter) and one 22 kW roots blower showed that purple color and odor problem can eliminate after almost two weeks and organic matter removal efficiency increased from 58 ± 15% to about 85 ± 10% based on BOD5. Almost similar results were obtained from the WSPs of Neyshabur. Long-term experimental results showed this system can be used successfully to control the process and upgrade these natural and efficient treatment processes, especially in developing countries.

Nutrient Removal in Sequential Batch Polishing Ponds

One of the main problems of waste stabilization ponds (WSP) is that they cannot remove nutrients when treating wastewater. Polishing ponds (PP) can efficiently remove nitrogen and phosphorus from effluents after efficient anaerobic pretreatment. It shown that the feasibility of nutrient removal is directly related to the pH that is established in the ponds. WSP normally operate at near neutral pH, but the biological processes that develop in PP tend to cause an elevation of pH and this, in turn, triggers the mechanisms of nutrient removal in ponds. In PP oxygen production by photosynthesis predominates over the oxidation of organic material. The net oxygen production has an equivalent CO2 consumption and this induces an increase in pH. The mechanism for nitrogen removal was identified as the desorption of ammonia from the liquid phase of the ponds. It was established that in ponds with a uniform concentration profile in the liquid phase the process developed in accordance with Fick’s law. The governing mechanism of phosphorus removal was precipitation with ions present in the wastewater, presumably calcium and magnesium. Polishing ponds can be operated with two different hydrodynamic regimes: flow-through (FTPP) and sequential batch (SBPP) ponds. The SBPP have the advantage that the pH elevation is more rapid, and that the final pH is higher.