Pump Stations for Housing Developments

commercial wastewater pumping station

Types of Pump Stations for Housing Developments

In order for a housing development to connect to the Irish Water Network to avail of wastewater services, there are codes of practice and standard details that must be followed. These codes and standards relate to the wastewater infrastructure within the development such as pipework, drains, manholes, inspection chambers, storage facilities and pump stations. They are important because they are based on best practice and the experience of local authorities in the provision of wastewater services. The same codes and standards also apply to commercial developments. In this article, we focus on pump stations for housing developments and some of the relevant codes and standards. For a proposed housing development, the site engineer will determine the appropriate requirements for a pump station. He/she will then supply these specifications to a reputable wastewater treatment company in order to provide a suitable pump station.

The table below lists the type of pump stations for housing developments to which the codes and standards refer:

Type Size No. of Dwellings Incoming Peak Design Flow
1 Small 5 or less 0.25 litre/second
2 Mid-range 6 to 20 0.25 – 1 l/s
3 Medium  >20 > 1 l/s

 

Note: Higher capacity pumping stations are not detailed in the codes and standards but still require the specific approval of Irish Water.

Housing Development Pump Station Cost

 

Pump stations for housing developments need to be cost effective and must be shown to cost less than a conventional gravity system in a net present value (NPV) assessment over 40 years. Not all new housing developments will require a pump station as a part of the sewerage works but in some instances, due to the topography of the area served, it is a necessity. If this is the case, the developer needs to provide evidence that the physical conditions of the site do not allow for full gravity works.

Impact on Existing Works, Emergency Storage and Overflow

When proposing and designing pump stations for housing developments, the impact on existing wastewater works in the area needs to be taken into consideration. It’s important that the action of the pump station does not compromise the capacity of the existing water network. Irish Water may request the provision of storage facilities at the pumping station to limit the effluent discharge into the public sewerage network.

In the event of flooding during pump or power failure, any resulting overflows have the potential to negatively affect the environment and must be minimized. Any provisions for emergency overflow situations must first be made in agreement with Irish Water and the EPA (Environmental Protection Agency) as part of the design proposal.

Pump Station Operation

 

A pump station for a housing development must have 100% standby capacity. This means it must have at least two or more submersible pumps on a duty/standby or duty/assist/standby arrangement. Provision for remote monitoring by telemetry should be made in order to transfer data to the Irish Water Control Centre. The system must have the capacity to detect alarm conditions and inform the appropriate parties.

The collection of data must include the following information:

  • Available/Run/Trip status for all pumps
  • Status for all float switches
  • Sump level
  • Instantaneous flow
  • Totalised flow
  • Mains Power Failure
  • UPS Fault/Healthy Status

Installation Works and Testing

During the construction of the pump station, field engineers for Irish Water will carry out site inspections. Onsite staff must keep a quality assurance folder containing the appropriate documentation relating to the installation. After the completion of installation works for any housing development pump station, Irish Water require proof that it is fit for purpose prior to any official use. A document package must be provided to Irish Water personnel prior to commissioning of the pump station. This package must include:

  • operation and maintenance manuals
  • as constructed drawings
  • control panel wiring diagrams
  • warranty documentation
  • full pump details including performance curves and power ratings

Conclusion

This article simply gives an overview of some of the main codes and standards for housing development pump stations required by Irish Water. The site engineer will ensure that the standards are met by providing the design specifications to the pump station suppliers who take care of the rest. The process of connecting to the water network has been made simple by Irish Water, simply visit https://www.water.ie/connections/get-connected/housing-development.xml to begin. The best time to start an application is prior to planning permission.

Disclaimer: This content is not a replacement for the full codes and standards which are available in full at the following links: https://www.water.ie/connections/Wastewater-Code-of-Practice.pdf and https://www.water.ie/connections/Wastewater-Standard-Details.pdf 

Designing a Dairy Wastewater Treatment Plant

dairy produce wastewater treatment systems

An In-House Dairy Wastewater Treatment Plant

The dairy industry uses massive amounts of water to processes raw milk for dairy produce and generates roughly 3 L of wastewater per 1 L of processed milk. It is one of the most polluting of industries, not just in terms of the volume of effluent but also in terms of the composition. Commercial dairies have two options – to pretreat and pay to discharge to municipal sewerage or to operate an in house treatment plant. However, there is no one size fits all solution. There are multiple possible configurations for a dairy wastewater treatment plant, selecting the correct one can be a challenge – but why?

In terms of biodegradability, dairy process wastewater is complex – it contains a combination of easily degradable carbohydrates and not so easily degradable proteins and fats. It is variable in pH also, rapidly changing from alkaline to acidic when lactose ferments to lactic acid. Dairies are multi product factories and the contents of pollutants in the wastewater will change with the start of each new cycle in the production process. This lack of consistency needs to be addressed by the treatment system.

Technologies Used in Dairy Wastewater Treatment

Dairy wastewater needs complex treatment prior to discharge in order to prevent environmental damage. This is due to the high concentration of organic materials including protein, carbohydrates, fats, grease and minerals that elevate BOD. Moreover, dairy factory cleaning processes generate wastewater containing detergents and cleaning agents that increase COD. Although there are many ways to reduce BOD and COD, biological treatment is the main method using aerobic, anaerobic or a combination of both technologies within a dairy wastewater treatment plant.

Steps in the Treatment of Dairy Wastewater

Mechanical treatment of dairy wastewater involves filtering out suspended solids with a mechanical screen. This reduces the organic load and protects the subsequent treatment equipment from blockages. An equalization/buffer tank will hold 6 – 12 hours of influent in order to smooth fluctuations in the flow. Supplying air at this stage helps to mix the wastewater and regulates the consistency for the next treatment stage. FOG removal usually follows flow balancing in a conventional dairy wastewater treatment plant.

Chemical treatment, also known as precipitation, removes colloids and soluble contaminants of dairy wastewater. This stage includes reagent oxidation or pH correction. Dissolved air flotation reduces organic loading with coagulants (Al2(SO4)3, FeSOand FeCl3) and flocculants. Here, controlling the pH is necessary to achieve the best conditions for coagulation (an acidic environment). However, the pH must be adjusted back to neutral levels before the next stage of treatment or can upset activity of microorganisms.

This completes the pretreatment of dairy effluent. It may be possible for a dairy to discharge suitably pretreated wastewater to a municipal treatment plant, with the approval of the relevant authority.

Biological Treatment Systems for Dairy Effluents

Biological treatment removes remaining impurities with the help of microorganisms. Aerobic systems use oxygen to breakdown the organic matter. Within the treatment system, air blowers supply the wastewater with oxygen, allowing the bacteria to multiply continuously. This process results in the formation of an activated sludge or biomass and the separation of clarified effluent. Most of the biomass is recirculated to maintain the biological process.

Dairy wastewater treatment plants often use an SBR system for aerobic treatment, due to its effluent flexibility and loading capability. The resultant effluent is ready for reuse or discharge, the excess sludge requires further treatment. Other aerobic systems include, fixed bed reactors, rotating biological contactors, trickling filters and moving bed biological reactors.

Anaerobic systems, on the other hand, do not require oxygen in order to break down organic matter and as such do not have the high energy requirements associated with aeration in aerobic systems. Other advantages of anaerobic digestion include the production of biogas (an energy source) and less sludge production. An example of a suitable anaerobic system for a dairy wastewater treatment plant is an anaerobic fixed bed reactor (AFBR) due to its capacity for microorganism retention and ability to cope with influent variations/shock loads.

However, anaerobic treatment is only suitable as a preliminary step in the biological treatment of dairy wastewater due to its weak effect on nutrient removal. It must be combined with a localized polishing step. Once aerobic/anaerobic biological treatment is complete, the residual sludge is sent for sludge treatment and disposal.

Cost Savings Associated with In-House Dairy Wastewater Treatment Plant

A study conducted by the Association of German Dairying in 2010 revealed that the costs associated with operating an in-house wastewater treatment plant were up to to 2/3 less than those of direct dischargers i.e. users municipal treatment plants. Ultimately, the most suitable treatment system depends entirely on the process and produce of the individual dairy. The costs associated with anaerobic systems are generally less but such systems are not suitable for all types of dairy effluent. The dairy processing handbook advises to contact local authorities at an early stage when planning a new plant to discuss discharge consents.

A reputable wastewater treatment company will be able to conduct the necessary tests in order to provide the most suitable and cost effective treatment system for a commercial dairy. A pilot scale system can be tweaked and tailored to suit the treatment requirements of a particular dairy before a full scale treatment system is put into place. Remember – every dairy is different!

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Foul Pump Stations Explained

domestic sewage effluent pump station

What is a Foul Pump Station?

Foul pump stations move wastewater from A to B in low gravity areas and are also known as lift stations. Wastewater flows downhill, but what happens if it needs to get back up to higher ground? This is where a foul pump station comes in – to give it a push to get there!

A typical foul pump station consists of a tank with an inlet, an outlet and one or more pumps inside that use electricity. When sewage enters the pump station and reaches a certain level, a float switch activates the pump. The pump then propels the wastewater to next point of call such as a sewer or a treatment plant.

Large wastewater pump stations include a control panel to allow for manual operation during maintenance work or repairs. During normal conditions, pumping stations operate on a single pump or set of pumps but will have back up pumps ready to take over in case a pump fails. This is known as built in redundancy.

Pumping stations are the most effective way to move wastewater. The size of the pump station and power of the pumps will depend on the volume and the type of wastewater to be pumped, so let’s take a look at at some different types.

Traditional Pump Stations

Older pump stations often consist of a wet well and a separate, adjacent dry well which houses the pumps. The wet well is the holding place for wastewater that flows via gravity and is hooked up to the pumps inside the dry well. Dry well pumping stations are no longer a popular option for two reasons:

  1. Confined underground space access – making maintenance and repair work tricky and hazardous
  2. Flooding risk – leaky pipework or pump failure can flood the dry well with sewage and cause expensive damage

It’s for this reason that wet well pump stations and wet wells with integrated pumps have come to replace traditional dry well pump stations. The pumps inside a wet well are known as submersible pumps and we’ll discuss these in the next section.

Submersible Pumps

 

As the name suggests, submersible pumps are submerged in wastewater. The motor in a submersible pump is carefully sealed to prevent any liquid from entering it and causing it to fail. Submersible pumps can be lifted to ground level using a chain and guide rail system which is much safer and easier than accessing pumps in a dry well for maintenance and repairs. Foul pump stations with submersible pumps operate across a huge variety of applications from domestic and light commercial to municipal and industrial. See below for the typical operational ranges of submersible pumps:

  • Flow rate ranges between 20 to 28000 lpm
  • Horsepower ranges between 1 to 250 hp
  • Total head (pressure) ranges between 0.4 to 6 Bar

 

Grinder Pumps

In some applications, it may be necessary for the foul pump station to be capable of handling solids. A grinder pump, typically used in domestic sewage pumping applications, will reduce solids in the wastewater to create a fine slurry which it will then pump to a septic tank or a sewer. In residential areas, one grinder pump station may serve multiple houses.

Packaged Pump Stations

 

A packaged pump station is a self contained system with all the internal pipework fitted inside a watertight, reinforced tank. After the tank is installed below ground, the submersible pump and control equipment are fitted and connected to the power supply. Once the inlet and outlet pipes are connected to the pump station it is ready to operate. Packaged foul pump stations are a very popular choice due to the ease of installation, access and maintenance. A reputable wastewater treatment company will often include service checks as part of the package.

Control Equipment

Pumping up to thousands of litres of wastewater and sewage on a daily basis will inevitably cause internal wear and tear. That’s why controls and alarms are essential equipment for foul pump stations. When the wastewater rises above a certain level an alarm will notify of a failure in the system. Suppliers may even offer a remote monitoring service with SCADA, the Supervisory Control & Data Acquisition system. This is particularly helpful with large foul pump stations that need close supervision and regular checks.

Do I Need Sewage Pump Station?

Foul pump stations are an essential part of wastewater treatment. Without pump stations, wastewater accumulates in low gravity areas, backs up pipes, overflows into buildings and floods land. Even if you weren’t aware of it, or unless you live on the top of a hill, there is probably a pump station close by! If you are building a new home and think you may need a foul pump station, get in touch with a local wastewater treatment company, they will advise you best. The same is true for commercial premises.