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Mechanical Process Engineer - Water​/Wastewater

Job in Fountain Valley, Orange County, California, 92728, USA
Listing for: Selectek
Full Time position
Listed on 2026-06-10
Job specializations:
  • Engineering
    Process Engineer, Environmental Engineer
Salary/Wage Range or Industry Benchmark: 95000 - 130000 USD Yearly USD 95000.00 130000.00 YEAR
Job Description & How to Apply Below
Position: Mechanical Process Engineer - Water / Wastewater

Needed Immediately:
Process Engineer in Fountain Valley, CA.

This role is responsible for leading the development of process designs from concept through detailed engineering, including simulation, hydraulic analysis, and full facility design.

The engineer in this position shall be capable of transforming process simulations into practical, constructible treatment plant designs, including development of hydraulic profiles, PFDs, P&IDs, equipment selection, and facility layouts. This position requires deep expertise in biological treatment systems, including activated sludge, MB  (Moving Bed Biofilm Reactor), and S  (Sequencing Batch Reactor) technologies, as well as advanced membrane systems such as microfiltration (MF), nanofiltration (NF), and reverse osmosis (RO).

The Senior Process Mechanical Engineer will coordinate closely with multidisciplinary teams and support both project execution and business development efforts, including technical input for proposals and client engagements and any other tasks assigned by the Director of Engineering.

Required Skills and Experience
  • Minimum 10–15 years of experience in wastewater treatment and water reclamation facility design.
  • Demonstrated experience in process modeling and simulation, preferably using Bio Win.
  • Extensive expertise and experience in designing activated sludge process (ASP) and biological nutrient removal (BNR) treatment including solids processing.
    • Specific types of systems include:
    • MBRMB
    • S
    • IFAS
    • Modified Ludzack-Ettinger (MLE)
    • Oxidation Ditch
    • Bardenpho
  • Experience with advanced treatment systems:
    • MF / UF
    • NF
    • RO
    • AOP
  • Proven ability to develop:
    • PFDs
    • Preliminary Design Reports
    • P&IDs
    • Hydraulic profiles

      Process calculations
  • Experience delivering projects from concept through IFC.
  • Strong understanding of applicable standards including:
    • AWWA
    • ASME
    • ANSI
    • WEF guidelines
  • Experience coordinating multidisciplinary teams.
Education and Certifications
  • Bachelor’s Degree in Chemical, Environmental, Mechanical Engineering, or Civil Engineering.
  • Professional Engineer (PE) license preferred in California, Arizona, Florida, or Colorado.
  • Advanced training or certification in process modeling software is an advantage.
Key Responsibilities 1. Process Engineering and Design Development
  • Lead process design development for wastewater and advanced water treatment facilities from conceptual design through Issued for Construction (IFC) deliverables.
  • Develop and execute process simulations using industry-standard software such as Bio Win or equivalent.
  • Model and design conventional activated processes with biological nutrient removal (BNR) treatment processes including:
    • Membrane Bio Reactor (M )
    • Moving Bed Biofilm Reactor (MB )
    • Sequencing Batch Reactor (S )
    • Integrated Fixed Film Activated Sludge (IFAS)
    • Bardenpho
    • Modified Ludzack-Ettinger (MLE)
    • Oxidation Ditch
  • Translate process models into detailed engineering designs, including:
    • Hydraulic Profiles
    • Process Flow Diagrams (PFDs)
    • Piping & Instrumentation Diagrams (P&IDs)
  • Perform process calculations, mass balances, and system performance evaluations.
2. Advanced Treatment Systems Design
  • Design and integrate advanced treatment systems including:
    • Microfiltration (MF)
    • Nanofiltration (NF)
    • Reverse Osmosis (RO)
    • Advanced Oxidation Process (AOP)
  • Develop process configurations for water reuse and advanced water reclamation facilities.
  • Perform membrane system sizing, recovery analysis, and fouling considerations.
  • Integrate biological and membrane processes into optimized treatment trains.
3. Equipment Sizing and Facility Design
  • Lead development of equipment sizing and selection, including:
    • Pumps
    • Blowers and aeration systems
    • Reactors and basins
    • Membrane systems
    • Chemical dosing systems
  • Develop and review treatment plant layouts, ensuring efficient process flow and maintainability.
  • Prepare and review:
    • General Arrangement (GA) drawings
    • Equipment layouts
    • Process system configurations
  • Integrate standard technical drawing details into design packages.
4. Project Delivery and Design Milestones
  • Lead process engineering deliverables through all project phases:
    • Conceptual Design
    • 30% Design
    • 60% Design
    • 90% Design
    • Issued for Construction (IFC)
  • Ensure process design deliverables meet project schedule, budget, and quality requirements.
  • Participate in and lead design reviews to validate process performance, constructability, and operational efficiency.
  • Support commissioning and startup activities as needed, including troubleshooting and performance optimization.
5. Multidisciplinary Coordination
  • Coordinate process design with:
    • Mechanical Engineers
    • Civil Engineers
    • Structural Engineers
    • Instrumentation & Electrical Engineers
    • CAD Designers
  • Provide process design input for instrumentation, controls philosophy, and system automation.
  • Ensure proper integration of process systems with electrical and control systems.
  • Resolve interdisciplinary design conflicts and ensure coordinated engineering deliverables.
6. Technical Leadership and Mentorship
  • Provide technical leadership and mentorship to junior and mid-level engineers.
  • Review and validate engineering…
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