Learn

 

If you are not entirely certain what you are looking for in regards to your wastewater needs, You've come to the right place! This segment of the site is purely dedicated to teaching you about the three major types of wastewater systems.

 

The three major wastewater systems are as follows:
 

What is a Decentralized System?

 

The Decentralized Approach to wastewater systems and management are individual or multiple self contained systems each including collection, treatment and disposal of wastewater and residual solids. Systems can vary in size from serving a small group of homes to systems serving over 1,000 homes. Decentralized systems are equal to larger conventional sewage collection and treatment systems in that they are subject to local, state and federal regulations and standards. The premise is that the final decentralized option should provide the same "look and feel" of a conventional wastewater system and offer a manageable and affordable alternative.

 

Typically, sewage treatment involves three stages, called primary, secondary and tertiary treatment. First, the solids are separated from the wastewater stream. Then dissolved biological matter is progressively converted into a solid mass by using indigenous, water-borne bacteria. Finally, the biological solids are disposed of or re-used, The final effluent can be discharged into a natural surface water body (stream, river or bay) or other environment (wetland, golf course, greenway, etc.). By utilizing a collaborative approach with equipment companies, land planners, engineers, Aqua Tech Systems finds the right balance between collection, treatment and disposal to determine the most appropriate system for a particular community or development.

 

Municipal System

 

Municipal wastewater treatment systems also referred to as conventional systems are typically highly engineered strategies and often focus on electro-mechanical solutions that are capital intensive and require ongoing capital investments for effective operation. They have shorter life-cycles compared to many alternative and naturally-based technologies which also offer opportunities for resource recovery.

 

Conventional waste water treatment typically involves some variation of the following unit operations and processes in the order given: 1) Collection; 2) Primary Settling; 3) Secondary aerobic treatment; 4) Secondary Settling; 5) Sludge digestion (either aerobic or anaerobic); 6) Sludge dewatering and disposal; 7) Effluent chlorination; 8) Effluent dechlorination; 9) Effluent discharge to a natural waterway. Variations on this flow train vary according to the regulatory environment of the municipality. In developing countries, sewage treatment plants are nearly always much more basic than what has been described above and represent severe environmental stress to the waterways that receive the poorly treated effluent.

 

Domestic wastewater management of any city consists of collection, treatment and disposal. In conventional centralized sewage treatment system, about 80% of the cost is accounted for the collection alone. The cost of collection of sewage and its conveyance to one terminal point in the larger cities is very high. Further, the depth of sewer goes on increasing with the increase in length of sewer line and pumping of the sewage at intermediate and terminal points requires a lot of energy. Further centralized treatment systems or conventional systems aggravate environmental problems, as large volume of the wastewater of the entire city is discharged at one place.

 

The replication of centralized, highly engineered human waste management systems are linked to sanitary reforms of the 19th century. The emergent trends towards low-cost, decentralized naturally-based wastewater systems promotes the recovery and reuse of wastewater resources and are becoming increasingly popular in meeting the needs of today's infrastructure requirements.

 

Onsite System

 

A septic tank, the key component of a septic system, is a small scale sewage treatment system common in areas with no connection to main sewerage pipes provided by private corporations or local governments. Septic systems are a type of On-Site Sewage Facility (OSSF). In North America approximately 25% of the population relies on septic tanks; this can include suburbs and small towns as well as rural areas. The term "septic" refers to the anaerobic bacterial environment that develops in the tank and which decomposes or mineralizes the waste discharged into the tank.

 

Periodic preventive maintenance is required to remove the irreducible solids which settle and gradually fill the tank, reducing its efficiency. In most jurisdictions this maintenance is required by law, yet often not enforced. Septic drain fields are used to remove contaminants and impurities from the liquid that emerges from the septic tank. This is typically done by burying perforated pipes in trenches and allowing the liquid to leach out and the surrounding soil absorbs the unwanted waste. Design of the septic drain field is determined by the size of the dwelling that it serves and the soil conditions.The soil conditions would be tested by a method called a perc test. An engineer or licensed designer may be required to work with the local governing agency to design a system that conforms to these criteria.

 

Drain field failure

Typical septic design

Solid matter entering tank slowly settles to the bottom of the tank if it's heavier than water or floats to the top if it's lighter than water. Fats and greases will tend to float. Some solids create problems. Vegetable material contains cellulose and is not readily digested by the bacteria in the septic tank. This causes solids to accumulate more rapidly. For this reason, garbage grinders are not recommended for homes having onsite sewage systems. Excessive hair is potentially problematic solid. Hair is generally neutral in bouyancy and neither floats or settles and presents clogging problems when present in large amounts. while most of the other solid matter will settle.

 

Anaerobic (without oxygen) digestion takes place and most of the solids are converted to carbon dioxide, water and other byproducts. The process is not completely efficient and solids will accumulate over time. The main cause of failure is neglecting to pump out the tank every one to three years. Excessive scum and sludge leak from a full tank of solid waste into the drain field and plug the sand, gravel and soil. This prevents the normal filtering of wastewater that enters the drain field - and the whole system backs up.

 

Two other main causes of failure are excessive water use over short time periods (many laundry loads or showers in one day) and adding harmful chemicals. As a high volume of wastewater enters the septic tank, an equal volume must exit into the drain field. This high volume churns the tank and the suspended sludge, scum and non-biodegradable products travel with the waste-water to clog the drain field. Other septic stoppers include improper design or installation, clogged or broken pump, frozen pipes, and saturated drain field soils, aging systems and limited space for the drain field.

 

 

Articles