Principal Process Engineer in London

Ayesa is a globally oriented, forward-thinking company deeply committed to fostering diversity, inclusion, equity, and sustainability. These principles form the bedrock of our dedication to our 13,000 employees and serve as the driving forces behind our spirit of innovation.

With a presence in 23 countries worldwide, Ayesa has earned a prominent international reputation in various engineering fields, including infrastructure, water conveyance and treatment systems, transportation, marine projects, waste management, aeronautics, and defense.

As a Principal Process Engineer within the Water Infrastructure Team, you will play a senior technical and leadership role, primarily responsible for the design, coordination, and delivery of process engineering solutions within water, wastewater, sewage treatment and utilities sectors, with the potential to expand into energy, transport, and environmental infrastructure sectors.

• Lead the process design for treatment plants, pumping stations, pipelines, and utility systems.
• Define treatment process schemes, undertake mass balance and hydraulic calculations, and specify equipment (e.g., aeration systems, chemical dosing, sludge handling).
• Ensure designs meet UK regulations, standards, and client specifications, such as DWI, EA, or Ofwat requirements.
• Carry out design reviews, challenge assumptions, and sign off key deliverables to ensure technical robustness.
• Oversee multidisciplinary coordination — integrating process design with civil, mechanical, electrical, and control system disciplines.
• Develop and manage process flow diagrams (PFDs), P&IDs, design reports, and technical specifications.
• Ensure all work aligns with BIM and digital design workflows where applicable.
• Present designs and/or scribe HAZOP, HAZID, and SIL studies.
• Lead or support design and build (D&B) projects, working closely with contractors, utilities and delivery partners.
• Manage project scope, schedules, and budgets while maintaining high technical standards.
• Oversee process commissioning, testing, and performance verification on site when projects move into delivery phases.
• Guide and mentor junior process engineers and graduates.
• Lead internal design reviews and promote best practices in process design, sustainability, and digital delivery.
• Engage directly with clients at a senior level — helping shape project briefs, proposals, and process solutions.
• Contribute to business development, proposal writing, and framework management with key UK utilities.

• Integrate within our multi-disciplinary design team to deliver robust design solutions to clients.
• Interface with other engineering disciplines including civil, M&E and structural.
• Communicate effectively with clients and senior staff.
• Manage a challenging workload.
• Be a team player with a mature approach including first‐class interpersonal skills.
• Adhere to all Codes of Practice, Design Standards and Health & Safety Regulations.
• Represent and promote Ayesa in a professional manner and develop effective working relationships with clients and potential clients.
• Manage projects in compliance with Ayesa's Integrated Management System (IMS).

• Minimum of 10 years' experience in water treatment and/or wastewater & industrial effluent treatment.
• Has achieved Chartered status.
• A degree and ideally a master’s in chemical/process or environmental Engineering.

• Deep understanding of the principles of water treatment and/or wastewater & industrial effluent treatment.
• Proven track record in the development of process solutions in industrial and municipal settings, and in accordance with specifications used in Ireland and the United Kingdom.
• Proven track record in process selection, process design, application engineering, proposal support and operational support.
• Proven track record in the development of the whole cycle of the treatment process from the concept to the detailed design stage.
• Has undertaken preliminary and detailed design of water / wastewater treatment plants based on data provided and achieved the desired treatment criteria.
• Demonstrate an ability to develop drawings of equipment and plant layouts as required — developing PFDs (Process Flow Diagrams) and P&IDs (Process & Instrumentation Drawings).
• Demonstrate an ability to develop process mass balance, hydraulic, energy, mechanical calculations as part of the detailed design.

• Competitive Salary commensurate with skills and experience.
• Hybrid Work Model (2–3 days from home).
• Flexible Hours 37.5 per week (Core: 10am–4pm Mon–Thu, 10am–3pm Fri).
• Professional Development and Chartership Support.
• Employee Assistance Programme (EAP).
• Sustainability & Innovation‐Focused Culture.
• Generous Annual Leave with Additional Days Based on Service.

Ayesa is proud to be an equal opportunity employer. We value and celebrate diversity in all its forms, including but not limited to age, disability, gender identity, race, religion or belief, sex, sexual orientation, and socio‐economic background or neurodiversity. We believe that a diverse workforce fosters innovation and stronger outcomes. We are committed to inclusive hiring practices, providing reasonable adjustments for applicants and employees with disabilities, and ensuring equal access to opportunities for learning, development, and progression across our organisation.