Sustainable Compliance: A Gated Method for Selecting Innovative Wastewater Technologies, with a Worked Application

Proven alternatives to the conventional approach to wastewater treatment are often available but the conventional design is still selected by default. This paper describes a gated selection method that a practising engineer can apply to a live project in order to decide whether to adopt an alternative technology and to justify that decision. The method is based on sustainable compliance i.e. meeting the regulatory limits with a margin whilst improving the lifecycle efficiency, resilience and cost. It separates the functions that a treatment system must perform from the technologies that could perform them, records the project constraints in a register at four levels and then takes each candidate through six gated stages: screen, verify, score, de-risk, specify and operate. Six pass/fail exclusion tests are applied to remove the obviously unsuitable options prior to scoring, so that a fatal flaw cannot be made up for by some other strength. The survivors are then scored on four criteria using explicit weighting rules, with limited evidence being represented as a range rather than a single value; the conventional baseline is scored only as a comparator, and a baseline that has failed a constraint is not eligible for selection. Residual risk that no party will own will route the decision back to an earlier stage and full scale performance data will be fed back as evidence for future projects. The effort is matched to the project through three tiers, from a one page screen for low consequence work through to a pilot-backed assessment with formal lifecycle costing where the failure of the technology would be serious or it is new to the region. The method is illustrated by a worked example of the selection between aerobic granular sludge and conventional activated sludge and is supported by a template for each stage. It makes no assumption that the innovative option is better than the conventional one; it simply requires that every adoption and every decision to stick with the default be evidence based, risk managed, and defensible. It is intended for the practitioner and in particular the practitioner in a resource constrained environment and is presented as a decision making method rather than an empirically validated model.