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Urban and Semi-Urban Planning in Developing Countries from a Water and Wastewater Treatment Point of View
Published in J. Rose, Water and the Environment, 2017
The relative performance measure of several conventional versus low-cost wastewater treatment systems is shown in Table X. Conventional systems such as activated sludge and trickling filter have a lower process efficiency and are vulnerable to shock loadings. Low-cost treatment systems, such as aerated lagoons and anaerobic lagoons, have a higher process efficiency and are highly suitable for high-strength industrial wastewater treatment, besides having the advantage of tolerating high organic loadings. Anaerobic lagoons, in particular, are highly suitable for extensive industrial wastewaters treatment.
Glossary of Terms
Published in Louis Theodore, R. Ryan Dupont, Water Resource Management Issues, 2019
Louis Theodore, R. Ryan Dupont
anaerobic lagoon: a waste stabilization pond that is devoid of dissolved oxygen and employed to stabilize high organic content wastes; these lagoons are deep with a small surface area to minimize oxygen diffusion into the liquid.
Anaerobic Digestion for Biogas Production
Published in Jay J. Cheng, Biomass to Renewable Energy Processes, 2017
Anaerobic lagoons are widely used for the treatment of animal wastewaters and municipal wastewater from small communities in warm climate areas. They are usually earthen structures with liners (usually plastics) at the bottom to prevent wastewater leaking to the soil and groundwater. As open systems, anaerobic lagoons are operated at different ambient temperatures. HRTs varies from 60 to 180 days. Although many anaerobic lagoons provide adequate treatment of the wastewaters, they generate serious environmental concerns about emissions of methane, ammonia, and odor (mainly from hydrogen sulfide and volatile organic acids). Covered anaerobic lagoons have the advantages of the anaerobic lagoon without the emission problem. They are actually low-rate anaerobic digesters, as shown in Figure 6.16. Covered anaerobic lagoons are normally operated under ambient temperatures in tropical and subtropical areas with HRTs of 50–70 days, depending on the average annual temperature. Most of the time psychrophilic anaerobic microbes are dominant in covered. As shown in Figure 6.16, wastewater enters the covered anaerobic lagoon on one end of the lagoon while the effluent exits from the other end. Three zones are usually formed in the aqueous phase during the anaerobic digestion. A mixed liquor of organic materials and suspended microbial cells is in the middle zone where active metabolism takes place. As the organic compounds are degraded by the anaerobic microbes to produce biogas, the microbes also grow themselves. The old microbes settle down to form a thick anaerobic sludge. The top zone in the lagoon is normally a supernatant with little solids. Usually no mechanical mixing is provided in covered anaerobic lagoons, but the rising of the biogas bubbles generated in the anaerobic digestion process provides some mixing in the mixed liquor (Fleming et al., 2002). Effluent exits the covered anaerobic lagoon from the supernatant with very little solids, so the anaerobic microbes stay in the lagoon for a very long time, resulting in a high SRT. High SRT and HRT make the covered anaerobic lagoon very flexible in organic loading and solid content in the wastewater, and increase the tolerance of the anaerobic microbes to the toxicities. High SRT also results in increased endogenous decay of the old microbes, which releases nutrients that can be utilized by the active microbes. As a result, the net yield of anaerobic microbes in the covered anaerobic lagoons is significantly lower than that in many other anaerobic digesters. The most important advantage of the covered anaerobic lagoons is that they are economical to build and operate. A main disadvantage is their relatively large volume and surface area.
Improved water quality and reduction of odorous compounds in anaerobic lagoon columns receiving pre-treated pig wastewater
Published in Environmental Technology, 2018
Ariel A. Szogi, John H. Loughrin, Matias B. Vanotti
Although research on odor mitigation technologies has major focus in reducing air pollutant and improving indoor air quality, there are a set of technologies suitable to reduce air pollutants outside the animal housing [8]. Among these technologies, solid–liquid separation and biological N treatment (nitrification–denitrification) are two methods that were evaluated to treat liquid pig manure prior to lagoon input [9]. An on-farm solid–liquid separation system that combined mechanical and chemical (flocculant addition) processes was reported to reduce solids prior to lagoon input by 85% and decrease annual ammonia emissions by 73% as compared to an anaerobic lagoon not receiving solid–liquid pre-treated wastewater [10,11]. On the other hand, an on-farm multistage wastewater treatment system using solid–liquid separation, nitrification/denitrification (biological N), and soluble phosphorus (P) removal processes was evaluated within an agreement between the North Carolina Government and several pig farming companies, called ‘environmentally superior technology’ (EST), to replace anaerobic lagoons in North Carolina. This multistage treatment system was the only on-farm technology certified to meet the high-performance EST standards to reduce the release of ammonia, phosphorus, heavy metals, pathogens, and odors into the environment [11,12]. It was reported to perform consistently well in wastewater odor removal [13,14]. The EST evaluation also included cost analyses that supported the North Carolina Government to establish a financial assistance program to pig producers for a lagoon conversion program [12,15]. The voluntary adoption of the solid–liquid separation plus biological N technology in Chile led to the conversion of 60% of their swine lagoons (1.3 million pigs) because of its additional advantage over anaerobic digestion systems of providing carbon offsets [16].