Wastewater
Wastewater, also written as waste water, is any water that has been adversely affected in quality by anthropogenic influence. Wastewater can originate from a combination of domestic, industrial, commercial or agricultural activities, surface runoff or stormwater, and from sewer inf…
Biochemical oxygen demand
Biochemical oxygen demand (BOD) (also called biological oxygen demand) is the amount of dissolved oxygen needed (i. e., demanded) by aerobic biological organisms to break down organic material present in a given water sample at certain temperature over a specific time period.
What is a pond used for in wastewater treatment?
Ponds have historically been used to provide long detention times (greater than 150 days) for wastewater to be stabilized through natural processes. Wastewater is treated by the action of bacteria (both aerobic and anaerobic), algae, other micro and macro organisms, and by the physical process of gravity settling.
How does a pond system work?
This large, floating plant can quickly cover the water surface of shallow ponds. Pond systems stabilize organic material through natural processes involving sunlight, water, nutrients, algae, atmospheric oxygen and bacterial action. Organic matter in the wastewater is broken down by aerobic bacteria and oxygen found in the pond.
Does wastewater include water released from ponds or reservoirs?
However, wastewater does not include water released from ponds or reservoirs for fish farming. Wastewater can be divided into two major groups: Sewage water is all wastewater used in domestic dwellings (e.g. originating from toilets, showers or sinks).
How does wastewater treatment work?
The Basics O ne of the most common forms of pollution control in the United States is wastewater treatment. The country has a vast system of collection sewers, pumping stations, and treatment plants. Sewers collect the wastewater from homes, businesses, and many industries, and deliver it to plants for treatment.
What is a water treatment pond?
A treatment pond is intended to provide wastewater treatment to achieve a certain effluent quality. Ponds are depressions holding water confined by earthen structures.
How do oxidation ponds work?
Oxidation ponds, also called lagoons or stabilization ponds, are large, shallow ponds designed to treat wastewater through the interaction of sunlight, bacteria, and algae. Algae grow using energy from the sun and carbon dioxide and inorganic compounds released by bacteria in water.
How do settling ponds work?
A settling pond is a basin or lagoon used in the wastewater treatment process where water can collect. Solid pollutants in this water settle to the bottom and excess water is allowed to flow over the top.
What are the 3 steps to wastewater treatment?
There are three main stages of the wastewater treatment process, aptly known as primary, secondary and tertiary water treatment. In some applications, more advanced treatment is required, known as quaternary water treatment.
Do sewage lagoons smell?
Septic sewage lagoon odors Seasonal lagoon turnover causes sludge and odors to rise to the surface. A raw sewage odor means lagoon failure: There is not enough DO or circulation to digest influent BOD, so waste just accumulates and digests anaerobically, which is slow and releases foul odors.
What is the difference between oxidation pond and oxidation ditch?
The key difference between oxidation pond and oxidation ditch is that oxidation ponds are large, shallow ponds that are designed to treat wastewater through the interaction of sunlight, bacteria, and algae, whereas oxidation ditch is a modified activated sludge that involves biological treatment processes utilizing ...
How waste stabilization ponds work?
Waste or Wastewater Stabilization Ponds (WSPs) are large, man-made water bodies in which blackwater, greywater or faecal sludge are treated by natural occurring processes and the influence of solar light, wind, microorganisms and algae . The ponds can be used individually, or linked in a series for improved treatment.
How do retention ponds reduce flooding?
Ponds can be designed to control runoff from all storms by storing surface drainage and releasing it slowly once the risk of flooding has passed. Runoff from each rain event is detained and treated in the pond.
What is ponding in wastewater?
A condition occurring on trickling filters when the hollow spaces (voids) become plugged to the extent that water passage through the filter is inadequate. Ponding may be the result of excessive slime growths, trash, or media breakdown.
Where does the water go once it is treated?
The treated wastewater is released into local waterways where it's used again for any number of purposes, such as supplying drinking water, irrigating crops, and sustaining aquatic life.
Is the water drinkable after it has been treated?
After treatment, the water is added to the reservoirs. NEWater, which has passed more than 65,000 scientific tests and surpasses World Health Organization drinking water standards, is clean enough to be used for the electronics industry and to be bottled as drinking water.
How is waste water treated?
Chlorine is the chemical most often used in treating sewage and other types of wastewater. The process is called chlorination. This is the most effective means of destroying a variety of viruses and bacteria. A method known as neutralization is effective when treating industrial wastewater.
How long does it take for sludge to dry out?
9. Sludge, digested and dewatered to the optimal degree, is finally disposed of at the dump. In about a month, sludge is adequately dried out and ripe. If it complies with agricultural standards, it can be reused for fertilisation of industrial crops.
How is wastewater drained to the WWTP?
1. Firstly, wastewater is drained to the WWTP by gravity through the main sewer system of the size of a car. Having such size, objects you could hardly imagine reach the WWTPs, ranging from mattresses, fridges, tree branches to wallets disposed of by thieves in order to get rid of the evidence. 2.
What is wastewater water?
Wastewater can be divided into two major groups: Sewage water is all wastewater used in domestic dwellings (e. g. originating from toilets, showers or sinks). Industrial wastewater originates from production, industrial and commercial activities, and has a different chemical composition to sewage water.
What is the first stage of wastewater treatment?
The first mechanical stage is called preliminary treatment or rather pre-treatment. Water flows through gravel chamber for settling out the grit from water. Afterwards, gravel is disposed of at the dump. Water further reaches the bar screens used to remove large objects from the wastewater.
What is wastewater in agriculture?
What is wastewater? It is used water originating from domestic, industrial, agricultural, and medical or transport activities. Used water becomes wastewater upon the change of its quality, composition and/or temperature. However, wastewater does not include water released from ponds or reservoirs for fish farming.
What is the purpose of bar screens in wastewater treatment?
Water further reaches the bar screens used to remove large objects from the wastewater. At first come the coarse screens and then the fine screens which remove smaller objects such as matches, cigarette butts or undigested foods. 3. After the removal of large objects, grit is to be removed from the wastewater.
What is secondary treatment?
The secondary treatment, also called biological stage, is based on natural processes. WWTPs use bacteria which consume the contaminants, in particular biodegradable organics, carbon and phosphorus. Dead bacteria and organic residues subsequently transform into sludge. 6.
How is wastewater applied to land?
In the slow-rate, or irrigation, method, effluent is applied onto the land by ridge-and-furrow spreading (in ditches) or by sprinkler systems. Most of the water and nutrients are absorbed by the roots of growing vegetation. In the rapid infiltration method, the wastewater is stored in large ponds called recharge basins.
How to remove algae from pond?
Algae remaining in the pond effluent can be removed by filtration or by a combination of chemical treatment and settling.
How is secondary effluent applied?
In some locations, secondary effluent can be applied directly to the ground and a polished effluent obtained by natural processes as the wastewater flows over vegetation and percolates through the soil . There are three types of land treatment: slow-rate, rapid infiltration, and overland flow.
What is effluent polishing?
For the removal of additional suspended solids and BOD from secondary effluent, effluent polishing is an effective treatment. It is most often accomplished using granular media filters, much like the filters used to purify drinking water. Polishing filters are usually built as prefabricated units, with tanks placed directly above the filters for storing backwash water. Effluent polishing of wastewater may also be achieved using microstrainers of the type used in treating municipal water supplies.
What is a polishing filter?
Polishing filters are usually built as prefabricated units, with tanks placed directly above the filters for storing backwash water. Effluent polishing of wastewater may also be achieved using microstrainers of the type used in treating municipal water supplies. tertiary treatment of wastewater.
What is tertiary treatment?
tertiary treatment of wastewater. (Left) During the filtering step, wastewater from secondary treatment, still containing suspended solids, pours from a trough and percolates through a filter bed made of porous media such as sand, gravel, and anthracite. The filtered water is then piped away for disposal.
How to remove ammonia from sewage?
A physicochemical process called ammonia stripping may be used to remove ammonia from sewage. Chemicals are added to convert ammonium ions into ammonia gas. The sewage is then cascaded down through a tower, allowing the gas to come out of solution and escape into the air.
What is a facultative pond?
Facultative stabilization ponds that receive raw wastewater are called primary facultative ponds. If they are receiving wastewater that has already been treated in anaerobic ponds, they are called secondary facultative ponds. Facultative stabilization ponds may also be used for treatment following other types of treatment processes such as upflow anaerobic sludge blanket (UASB) reactors, oxidation ditches or aerated lagoons. Compared with anaerobic ponds, facultative ponds are shallower (1.5 to 2.5 m deep) and have much larger surface areas. The surface area is important because it allows atmospheric oxygen to dissolve and sunlight radiation to penetrate the water. This allows for photosynthetic activity to occur which produces more oxygen.
What is anaerobic stabilization pond?
The depth decreases the influence of oxygen production by photosynthesis, leading to anaerobic conditions. Depending on loading and climatic conditions, these ponds are able to remove between half to two thirds of the influent BOD. This significantly decreases the load of organic matter that goes to the facultative ponds, and thus decreases their required size. Anaerobic stabilization ponds have the disadvantage of potentially releasing malodorous gases. This especially includes hydrogen sulfide with an odor of rotten eggs, if the system has operational problems.
What is the second type of pond?
The second type of pond, facultative stabilization ponds, sustain an aerobic surface habitat above an anaerobic benthic habitat. Maturation ponds offer aerobic conditions throughout, from the surface to the bottom. The main configurations of pond systems are: Facultative pond only;
What type of ponds have oxygen?
Anaerobic waste stabilization ponds have very little dissolved oxygen, thus anaerobic conditions prevail. The second type of pond, facultative stabilization ponds, sustain an aerobic surface habitat above an anaerobic benthic habitat. ...
How often should sludge be removed from a pond?
In facultative ponds, sludge removal may be necessary only in intervals around 15 to 25 years. In maturation ponds, sludge accumulation is very low.
What is the name of the pond where wastewater enters?
Wastewater or "influent" enters on one side of the waste stabilization pond and exits on the other side as "effluent", after spending several days in the pond, during which treatment processes take place. Waste stabilization pon ds are used worldwide for wastewater treatment and are especially suitable for developing countries ...
How efficient are waste stabilization ponds?
Waste stabilization ponds are very efficient in their primary objective of removing organic matter and, under some conditions, pathogenic organisms. Their design criteria have changed very little over the years. Ponds are simple to design, build, operate and maintain, which is very important in remote areas and in developing countries where sophisticated equipment and highly skilled labor is not easily available. Construction may be done by local contractors in small towns.
What is anaerobic treatment?
Anaerobic wastewater treatment is used to treat a variety of industrial effluent streams from agricultural, food and beverage, dairy, pulp and paper, and textile industries, as well as municipal sewage sludge and wastewater. Anaerobic technologies are typically deployed for streams with high concentrations of organic material (measured as high BOD, ...
What is anaerobic wastewater treatment?
Anaerobic wastewater treatment is a biological process where microorganisms degrade organic contaminants in the absence of oxygen. In a basic anaerobic treatment cycle, wastewater enters a bioreactor receptacle. The bioreactor contains a thick, semi-solid substance known as sludge, which is comprised of anaerobic bacteria and other microorganisms.
What are the two phases of methane production?
The second phase, known as the methane-production phase, consists of two steps: acetogenesis , where anaerobes synthesize organic acids to form acetate, hydrogen gas, and carbon dioxide; and methanogenesis, where the anaerobic microorganisms then act upon these newly-formed molecules to form methane gas and carbon dioxide.
How deep are anaerobic lagoons?
Anaerobic lagoons. Anaerobic lagoons are large man-made ponds, typically ranging between 1-2 acres in size, and up to 20 feet deep. They are used widely for treatment of agricultural wastewater resulting from meat production, as well as treatment of other industrial wastewater streams, and as a primary treatment step in municipal wastewater ...
What are the factors that affect the rate of anaerobic respiration?
The rate of anaerobic respiration can also be limited by a number of factors, including fluctuations in BOD/COD concentration, and presence of substances such as sodium, potassium, calcium, and magnesium.
Where is wastewater piped?
Wastewater is typically piped into the bottom of the lagoon, where it settles out to form an upper liquid layer, and a semi-solid sludge layer. The liquid layer prevents oxygen from reaching the sludge layer, allowing a process of anaerobic digestion to break down the organic materials in the wastewater. On average, this process can take as little ...
How does an aerated lagoon work?
An aerated lagoon is a stabilization pond with its aerobic condition maintained by mechanical or diffused aeration equipment . Bubble aeration is provided sometimes to keep the pond aerobic in locations where pond surfaces are frozen for extended periods in winter. Unlike aerobic ponds, aerated lagoons do not rely on algae for oxygen delivery. The microbial characteristics of an aerated pond are very similar to those of an activated sludge process. Its detention times are in the order of1 to 10 days, depending on organic loading rate, temperature, and the degree of treatment required. The organic loading of aerated lagoons is expressed as BOD5 per unit volume per day. Aeration ponds are susceptible to a large amount of BOD5 loadings or toxic wastes, which can severely hinder the ponds' efficiency. The solids in the pond need to be suspended all the time to avoid the solids settling in the bottom of the pond and forming an anaerobic layer, thus reducing the efficiency and generating odor. Fig. 6.3 shows a schematic portrait of an aerated lagoon and a photo of an aerator at work in an aerated pond.
What are the five categories of stabilization ponds?
All use microorganisms to degrade and decontaminate organic and inorganic constituents; the types of organisms as well as the amount of oxygen present in the pond systems differ among the five categories forming the basis for classifying stabilization ponds: • Facultative ponds. • Maturation ponds. • Aerated ponds.
How does a facultative pond work?
The facultative ponds are the most common type of stabilization ponds in use and are able to completely treat both raw, settled sewage and a wide range of industrial wastewaters, including food and agricultural waste -waters with detention time of 5-30 days. These ponds have depth ranging from 1.2-1.5 m (4-8 ft), consisting of two layers of biological treatment zones: an aerobic layer on top of an anaerobic layer, often containing sludge. The aerobic layer stabilizes the wastewater while the fermentation takes place in the anaerobic layer. The oxygen needed for aerobic stabilization comes from photosynthesis of algae in the pond (Fig. 6.2). The algae are photosynthetic organisms and therefore provide a source of oxygen for use by heterotrophic bacteria in the pond for the aerobic breakdown of organic matter. Respiration of organic matter provides a source of carbon dioxide for the algae. This symbiotic relationship between the algae and the bacteria provides the basis for this natural method of waste-
How many WSPs are there in France?
In France, there are approximately 2,500 WSPs in operation throughout the country, mostly for small communities (Racault et al., 1995). The capital and operational costs of WSPs are lower than other comparable wastewater treatment technologies (Mara and Pearson, 1998). Waste stabilization ponds can be used alone or in combination ...
What is the treatment phase for algae?
Because algae in the discharged effluent need to be removed, the treatment process usually involves a facultative pond, one or two maturation ponds and a tertiary treatment phase, such as rock filters or intermittent sand filtration for the removal of algae before discharge of the final effluent to an adjacent watercourse.
What is a stabilization pond?
Stabilization ponds suitable for wastewater treatment are those that maintain the right biological conditions for biological interactions and reactions that break down the organic matters and inorganic nutrients. There are five basic types of WSPs.
What is a WSP?
A WSP is a relatively shallow body of wastewater contained in an earthen man-made basin into which wastewater flows and from which, after a certain retention time (time that takes the effluent to flow from the inlet to the outlet), a well-treated effluent is discharged. Many characteristics make WSPs substantially different from other wastewater ...
What is a fine bubble diffuser?
Fine bubble diffusers typically have thousands of tiny holes and produce the smallest bubbles. The smaller bubbles provide the maximum surface area for contact with the wastewater. They also rise to the surface at a slower rate which provides for a longer contact time. These two factors make fine bubble diffusers the best choice for what is called “Oxygen Transfer Efficiency”. Oxygen transfer efficiency is the amount of air absorbed by the wastewater as a percentage of the amount of air produced by the aeration system.
How does aeration work in activated sludge?
Aeration in an activated sludge process is accomplished by pumping air into the tank or lagoon. Proper aeration promotes the growth of microorganisms or microbes in the wastewater. The microbes feed on the organic pollutants and form flocs which can easily settle out. The flocs are allowed to settle out in a separate settling tank or lagoon.
How does a subsurface aeration system work?
A sub-surface aeration system provides oxygen to microorganisms by injecting air into the wastewater. Blowers or air pumps compress the air which is delivered through airlines to diffusers installed on the bottom of the tank or lagoon. The diffusers are installed in a pattern on the bottom of the tank or lagoon for uniform coverage. The diffusers have tiny holes that create bubbles that come into contact with the water. Diffusers come in two basic types: fine bubble and course bubble.
What is a laminar flow diffuser?
This type of diffuser has thousands of tiny openings that create small fine bubbles at low flow. A laminar flow of small bubbles is advantageous in that they have a greater surface area for the absorption of oxygen into the water.
Why do bubbles have a greater surface area?
Also, because the smaller bubbles have a greater surface area, the laminar flow of bubbles pushes water vertically to create a columnar flow of water. The Duraplate™ Diffuser directs the laminar flow of bubbles and assists in creating a columnar flow of water that is drawn from hole at the bottom of the tube.
What is wastewater aeration?
Wastewater aeration is the process of adding air to assist the aerobic microorganisms in the consumption of pollutants. Wastewater aeration is a vital part of most every biological treatment system. A well designed and operated wastewater aeration system will accomplish two main jobs:
What is the second job of wastewater aeration?
The second job of wastewater aeration is mixing the wastewater. Proper mixing keeps solids in suspension thus avoiding a buildup of sludge. Mixing also ensures that there are no anaerobic (without air) zones in the wastewater. A common problem, especially with lagoons, is that there is less oxygen present on the bottom.
