Wastewater treatment: a compact, pre-engineered solution

By integrating screening, grit removal, and grit washing into a single, efficient wastewater treatment unit, these systems simplify design, reduce installation time, and lower long-term costs. Rich MacGregor highlights key features like configurability, component compatibility, and built-in safety, while emphasising benefits for engineers, contractors, and municipalities seeking reliable, high-performing, and easy-to-maintain solution

The need for effective headworks systems has become more critical than ever for wastewater treatment plants, driven by challenges such as the increasing prevalence of flushable wipes and the necessity to safeguard newer, more advanced treatment methods. 

For municipalities with small and medium-sized populations or in rural locations, designing state-of-the-art systems and navigating complex construction projects can be particularly daunting. This is where all-in-one headworks solutions offer a game-changing advantage. 

These integrated systems provide a complete system with a compact, efficient, and proven design, providing municipalities with a reliable, durable, and cost-effective solution. The industry’s most advanced all-in-one headworks solutions combine screening, grit removal, and grit washing into a seamless, fully integrated system. 

Pre-assembled and pre-tested, these stainless-steel units arrive on a skid ready for installation, delivered directly to the job site on a single truck. This efficient process guarantees municipalities access to the most advanced headworks technology, along with the confidence of timely, on-budget installation and smooth operation.

All-in-one headworks systems provide significant benefits to engineering firms, construction contractors, and municipalities in rural areas and in small communities. 

Regional engineering firms that serve rural locations no longer need to invest time and resources in developing specialised expertise to stay current with the latest in grit removal technology or designing intricate headworks systems they may only encounter infrequently. Instead, they can focus on their core strengths, such as infiltration/inflow (I/I) projects. This approach enables firms to broaden their service offerings without overextending their resources, while still providing municipalities with reliable, state-of-the-art headworks solutions.

Construction contractors benefit from simplified installation processes. Unlike traditional site-built systems, these pre-assembled solutions come ready to install, minimizing concrete pouring except the pad. This reduces construction risks, saves time, and eliminates costly rework, enabling contractors to complete projects efficiently and confidently.

For municipalities, pre-engineered headworks systems ensure a state-of-the-art wastewater treatment solution that is dependable and easy to maintain. With proven system design and integrated controls, these systems offer predictable performance and streamlined operations. Municipalities gain confidence in their wastewater systems, knowing they are equipped with modern, efficient technology that supports long-term functionality and sustainability. 

Importance of each component

A well-designed headworks system comprises three critical components: screening, grit removal, and grit washing. Each of these components plays a vital role in ensuring the efficient and effective treatment of wastewater.

1. Screening. Screening is the critical first stage of the wastewater treatment process, designed to remove large solid materials and debris from the flow of wastewater. Objects found in wastewater, including sticks, rags, plastics, cans, paper, and other debris, can wreak havoc on the system if not screened out early. Without this initial filtration, these items could cause severe blockages, mechanical failures, or inefficiencies in the treatment process, leading to costly repairs and operational disruptions.

Screening not only protects equipment but also ensures smooth and uninterrupted water flow throughout the system. For example, plastics don’t break down naturally and can impede the treatment process, while fibrous materials such as rags can wrap around moving parts, causing them to malfunction. Even natural debris like leaves or branches must be removed, as they could accumulate and obstruct the flow. 

Packaged headworks systems typically employ one of three different types of screens. 

• Basket screens, which use ultra-high molecular weight brushes, are a more economical option but come with higher operational costs. 
• Drum screens, designed with perforated plates, are versatile and can be used for both coarse and fine screening. 
• Mechanical bar screens, made with stainless steel bars spaced at 6mm or 1/4-inch, are considered a “workhorse” solution ideal for larger plants. Although they have a higher initial capital cost, they offer lower operational costs in the long run.

Fine screening is often necessary to safeguard sensitive treatment processes like Membrane Bioreactors (MBRs). Even small objects, such as a toothpick, can slip through vertical bars and damage the membrane. For fine screening, basket and drum screens are ideal, offering openings as small as 2-3mm. On the other hand, mechanical bar screens are better suited for coarser applications, with openings of 6mm or 1/4-inch.

2. Grit Chamber. Grit removal is a critical process in wastewater treatment headworks, designed to eliminate abrasive particles like sand, gravel, and silt from incoming flows. Without effective grit removal, these materials can damage equipment, reduce the capacity of treatment systems, and increase maintenance costs. Accumulated grit also leads to blockages and inefficiencies in downstream processes, negatively impacting overall plant performance.

Innovative technologies, like the Smith & Loveless PISTA Grit Removal System, have significantly enhanced efficiency and performance. The proprietary S&L vortex grit chamber geometry induces a true forced vortex flow pattern, which sweeps grit hydraulically along the floor toward the center opening to the lower collection/storage hopper. The PISTA Grit Chamber’s vortex action results in the industry’s highest removal efficiencies for particles as small as 75 and 100 microns (depending on project requirements).

The groundbreaking design minimizes energy consumption while significantly reducing wear and tear on pumps and mechanical systems. These advancements not only protect vital infrastructure but also improve the longevity and reliability of wastewater treatment facilities. 

3. Grit Washing and Dewatering. Grit washing improves the grit removal process by cleaning the collected grit to enhance its quality. This process separates organic matter from grit particles, reducing odors and minimisng odour-related problems at treatment plants. 

Advanced grit washing systems remove abrasive particles, extend the lifespan of downstream equipment, and reduce maintenance costs. Using cutting-edge separation techniques, these systems ensure treated water meets strict environmental standards, optimizing wastewater management while supporting sustainability.

State-of-the-art grit washing and dewatering achieves a 95% removal efficiency for particles as small as 75 microns, with only 3-5% putrescible organic material in the washed grit and less than 10% water content in the cleaned grit. 

By producing cleaner grit, grit washing reduces equipment wear and blockages, improving the overall performance and durability of wastewater treatment systems. For plants with total nitrogen limits, grit washing offers an additional benefit by increasing Biological Oxygen Demand (BOD) levels. This reduces reliance on external carbon sources like methanol, which can be both expensive and hazardous.

Configurability

An all-in-one headworks system needs not sacrifice customization, even if it is not custom-designed by a local engineering firm. These systems can still be tailored to meet specific requirements without compromise. 

To achieve this level of optimisation — addressing factors like flow rate, effluent quality, installation costs, and ongoing maintenance effort and expense—manufacturers should provide a range of options for each key component. This flexibility ensures the system aligns with the unique demands of every installation.

Screening: Specifiers and end users should have the option to select from basket screens, drum screens, or mechanical bar screens. Each type offers distinct advantages, such as cost-effectiveness and the capability for fine screening. 

Grit Chamber: Advanced grit chamber designs should be available, offering options for enhanced grit removal efficiency and adaptability to different flow conditions and downstream treatment processes. For example, the S&L PISTA Works system offers three advanced options for grit chamber technology: the PISTA INVORSOR, PISTA VIO, and PISTA 360 with V-FORCE Baffle. Selecting the right grit removal chamber is essential to safeguard and enhance advanced treatment processes such as MBR, RSS, and granular sludge systems. Without proper grit removal, debris can damage MBR membranes and disrupt sludge settling performance.

Grit Washing and Dewatering: Effective solutions include a robust grit pump designed to handle the demands of transporting grit slurries, paired with a highly efficient grit concentrator that serves as the primary tool for washing and dewatering. Like other essential components, it’s crucial to configure this stage of the process to achieve the optimal solution for each installation. High efficiency options such as a grit washer or a dewatering screw conveyor should be available to ensure the delivery of dry, clean grit with less than 5% organic content and a 95% grit retention rate. 

Design flexibility 

An all-in-one headworks system’s compact design is only part of what makes it integrate seamlessly into a site. Equally important is its ability to easily integrate into existing infrastructure. The S&L PISTA Works sets itself apart with the allowance of different screening, grit chamber and washing and dewatering component selections. This adaptability allows the PISTA system to meet the unique requirements of virtually any site for application up to 7MGD in flow.

Bypass and redundancy

Bypass and redundancy features are useful in any headworks systems, streamlining maintenance and significantly reducing downtime.

One of the most valued features of PISTA Works is its manual bar screen bypass, a built-in solution that ensures seamless operation even during routine maintenance or unexpected screen failures. By switching to the manual bar screen, facilities can avoid shutdowns and maintain system efficiency. Even brief periods without proper screening can cause chaos — allowing debris to pass through and resulting in major disruptions and damage to downstream processes.

Some customers choose redundant screens to ensure continuous operation during maintenance or equipment failures, eliminating the need for maintaining a manual bar screen. Additionally, incorporating a grit chamber bypass allows maintenance of grit removal equipment without disrupting overall plant operations.

These features are especially valuable for smaller plants with limited staff, as they prevent major disruptions, ensure consistent performance, and allow for ongoing maintenance without compromising functionality. 

Component compatibility

Component compatibility is key to the efficiency and performance of a headworks system. A well-designed all-in-one headworks system ensures seamless integration of components like grit removal, screening, grit chambers, pumps, and washers or classifiers. 

When components are not performance-matched, the system’s efficiency suffers—for example, when a grit chamber operates at 95% efficiency, but the grit washer only reaches 50%, the overall performance is significantly reduced. 

This issue is too often an issue with custom-designed site-built systems where components from multiple suppliers may not work together effectively. A high-quality all-in-one system avoids these problems by carefully engineering, sizing, and matching components to work harmoniously. 

Complete packaged solution

An effective all-in-one headworks system should provide a complete, integrated solution that is both easy to install and operate. 

Safety Features. Well-designed systems come pre-equipped with essential safety components such as platforms, handrails, ladders, and emergency stop mechanisms. These features are thoughtfully integrated into the design, ensuring they work seamlessly rather than being an afterthought. Not only do they reduce the need for engineering firms or contractors to design and install these features separately, but they also make maintaining the system much easier, while reducing liability concerns and ensuring compliance with OSHA regulations.

Integrated Intuitive Controls. Integrating all components into a single PLC-based control panel streamlines operations by eliminating the need for multiple, separate systems. A user-friendly graphical user interface and multilingual support — particularly in Spanish — minimises system complexity, simplifies training, and improves the efficiency of troubleshooting.

Factory wiring. Factory wiring and UL certification simplifies installation. Pre-installed conduit and electrical components further ease the process by eliminating the need for contractors to embed conduit in concrete or manage extensive on-site electrical work.

All-in-one Headworks systems offer transformative benefits for engineering firms, construction contractors, and municipalities. By simplifying design, streamlining installation, and delivering advanced wastewater solutions, these systems ensure projects are completed on time and within budget. Built for ease of operation and maintenance, they combine efficiency with cost-effectiveness, making them economical to run over the long term. By reducing complexity and enhancing performance, these systems save time, mitigate risks, and provide sustainable, high-performing technology designed for lasting success.

Rich MacGregor is a Technical Writer with Smith & Loveless.