Global Lagoon Water Treatment Brochure and Specification

Global Mold Inc. For Orders or Information Call or Send Email 208-687-4002 Sales@GlobalMoldInc.com www.globalmoldinc.com Lagoon Water Treatment For More Information Contact Global Mold, Inc at 208-687-4002 or Sales@GlobalMoldInc.com Lagoon Water Treatment Lagoons are pond-like bodies of water or basins designed to receive, hold, and treat wastewater for a predetermined period of time. If necessary, they are lined with material, such as clay or an artificial liner, to prevent leaks to the groundwater below. In the lagoon, wastewater is treated through a combination of physical, biological, and chemical processes. Much of the treatment occurs naturally, but some systems use aeration devices to add oxygen to the wastewater. Aeration makes treatment more efficient, so that less land area is necessary. Aerators can be used to allow existing systems to treat more wastewater. Dissolved oxygen is present throughout much of the depth of aerobic lagoons. They tend to be much shallower than other lagoons, so sunlight and oxygen from air and wind can better penetrate the wastewater. In general, they are better suited for warm, sunny climates, where they are less likely to freeze. Wastewater usually must remain in aerobic lagoons from 3 to 50 days to receive adequate treatment. Wastewater treatment takes place naturally in many aerobic lagoons with the aid of aerobic bacteria and algae. Because they are so shallow, their bottoms need to be paved or lined with materials that prevent weeds from growing in them. Aerated lagoons are common in small communities. These systems use aerators to mix the contents of the pond and add oxygen to the wastewater. They are sometimes referred to as partial-mix or complete-mix lagoons depending on the extent of aeration. Partial-mix aerated lagoons are often anaerobic lagoons that have been adapted and upgraded to receive more wastewater. Facultative Lagoon Like most natural environments, conditions inside facultative lagoons are always changing. Lagoons experience cycles due to variations in the weather, the composition of the wastewater, and other factors. In general, the wastewater in facultative lagoons naturally settles into three fairly distinct layers or zones. Different conditions exist in each zone, and wastewater treatment takes place in all three. The top layer in a facultative lagoon is called the aerobic zone, because the majority of oxygen is present there. How deep the aerobic zone is depends on loading, climate, amount of sunlight and wind, and how much algae are in the water. The wastewater in this part of the lagoon receives oxygen from air, from algae, and from the agitation of the water surface (from wind and rain, for example). This zone also serves as a barrier for the odors from gases produced by the treatment processes occurring in the lower layers. The anaerobic zone is the layer at the very bottom of the lagoon where no oxygen is present. This area includes a layer of sludge, which forms from the solids that settle out of the wastewater. Here, wastewater is treated by anaerobic bacteria, microscopic organisms, such as certain protozoa, and sludge worms, all of which thrive in anaerobic conditions. For More Information Contact Global Mold, Inc at 208-687-4002 or Sales@GlobalMoldInc.com Names for the middle layer include the facultative, intermediate, or aerobic-anaerobic zone. Both aerobic and anaerobic conditions exist in this layer in varying degrees. Depending on the specific conditions in any given part of this zone, different types of bacteria and other organisms are present that contribute to wastewater treatment. Throughout facultative lagoons, physical, biological, and chemical processes take place that result in wastewater treatment. Many of these processes are interdependent. For example, on the surface, wind and sunlight play important roles. Surface agitation of any kind adds oxygen to the wastewater. For this reason, facultative lagoons are designed to make the best use of wind in the area. Mixing of Water in Lagoons Mixing and aeration of water in the lagoon is important to prevent algae growth. Without mixing thermo stratification will occur, thereby permitting the retention of undisturbed surface layers for relatively long periods of time. Such conditions provide an excellent environment for algae to become established and grow. Relevance of Nitrification and De-nitrification in Lagoons Nitrification is the process of converting the ammonium in the water to nitrates/nitrites. Some nitrification generally occurs in most aerated lagoons. However, such nitrification is usually unpredictable and cannot be depended upon to meet effluent limits, especially during the winter months. Therefore, for aerated lagoons to be considered as viable processes for nitrification, the lagoon process must be modified so that the solids age is uncoupled from the hydraulic retention time (HTR). To enable efficient nitrification and subsequently de-nitrification, which is the conversion of nitrates/nitrites to nitrogen gas, and to decouple the solids age from the Hydraulic Retention Time (HRT), the use of biomedia in the lagoon is very important. This biomedia, which has a high surface area, enables biofilms to grow on the surface of the biomedia, and this attached biomass stays in the lagoon for a very long time, i.e., almost infinite solids age, while the water continues to flow through the lagoon, at its Hydraulic retention time. This allows the solids age to be decoupled from the lagoon’s HRT. Application of Biomedia in Lagoons Global Mold and PRD Tech, Inc. have pioneered a unique biomedia that has a very high surface area that stays within the lagoon water. It consists of a cable, with a heavy weight at the bottom and a flotation balloon at the top. This cable is threaded through biomedia plates, thereby allowing the biomedia to move in a wave-like fashion without flowing with the water. Since the cable is threaded through the cable, which stays in place due to its weight at the bottom, the biomedia moves around but essentially stays in a given location. This allows the water to be treated by the biofilms that coat the biomedia, as it waves around in the water. For More Information Contact Global Mold, Inc at 208-687-4002 or Sales@GlobalMoldInc.com Figure 1 shows the biomedia within the lagoon water. In addition, the biofilms on the surface of the biomedia allow nitrification and de-nitrification of the water, as it flows past the biomedia waving around in the water. This allows effective water treatment, without pumping the water out of the lagoon Aeration and Mixing of Lagoon Water The transfer of oxygen from the air bubble to the water depends on wastewater characteristics: (1) concentration of soluble salts (Total Dissolved Solids or TDS), water temperature, water depth, total suspended solids (TSS), presence of surface active agents, etc.; (2) tank geometry, bubble size, kinetic energy of the fluid, etc.; and (3) extent and type of liquid mixing with the bubbles, which determines the path length of the air bubble. The Actual Oxygen Transfer Rate (AOTR) = Standard Oxygen Transfer Rate (SOTR) x a x ß x ? where SOTR is the oxygen transfer rate for pure water, a is the parameter that depends on the type of aeration device, intensity of mixing and tank geometry, ß is the parameter that corrects for TDS, TSS, concentration of surface active agents, and ? is the parameter that adjusts for the oxygen solubility as a function of water temperature. Table 1 lists the SOTR values for typical aerators, including the Absorption Aerator aeration system. Type of Aeration System SOTR Value Surface Aerator with draft tube 1.2 – 2.1 Surface high speed 1.2 – 2.0 Submerged turbine 1.0 – 2.0 Submerged turbine with sparger 1.2 – 1.8 Surface brush and blade 0.8 – 1.8 Fine bubble diffusers 0.5 – 1.5 Coarse bubble diffusers 0.3 – 0.8 Absorption Aerator 2.7 – 3.1 For More Information Contact Global Mold, Inc at 208-687-4002 or Sales@GlobalMoldInc.com The Absorption Aerator’s basic mechanism is to pump liquid water through a specially designed nozzle in which the high velocity of the liquid combined with swirl flow creates a negative pressure that draws in ambient air which is dispersed in the form of micro bubbles (less than 50 µm in diameter). Figure 2 shows the basic schematic of the Absorption Aerator with its micro bubble generation mechanism. Figure 2. Basic mechanism of the Absorption Aerator. The Absorption Aerator has a high oxygen transfer efficiency due to the following factors: (1) high gas/liquid ratio = 2.2:1.0; (2) high intensity of mixing in the nozzle system; (3) no external blower required, which has major maintenance requirements; (4) the micro bubbles have a large residence time within the water, thereby allowing the dissolved gases in the water, such as carbon dioxide, hydrogen sulfide, etc. to be effectively stripped out; and (5) 50 µm or smaller bubbles ultimately dissolve completely, creating an implosion that creates hydroxyl radicals; these radicals effectively treat the contaminants in the water, such as hydrolysis of fats and oils, oxidation of ammonia, which promotes biological activity. Figure 3 shows an Absorption Aerator system for a pond aeration, in which water is taken from one end of the pond through intake pipes (not shown in the photograph), and then pumped through the Absorption Aerator, wherein it mixes with the ambient air that is drawn in by the water flow, and then this water with micro bubbles is discharged back into the pond through discharge nozzles (not shown). Figure 3. Photograph of an Absorption Aerator system for a pond. Global Mold, Inc. can supply a complete lagoon treatment system, which consists of the biomedia that waves around in the water, together with an Absorption Aerator system that can effectively supply oxygen to the water using micro bubbles. Absorption Aerator Gorman Rup Pump 4 inch Absorption Aerator Water Discharge Pipe