1. First, You Must First Define the Goals & Objectives

DESIGN OBJECTIVES

Your goal is to find the best solution to meet the Client’s wastewater treatment needs over the next 20 years. How do you design a solution that optimally achieves the goals & objectives of the project?

1. First, you must first define the goals & objectives.

GOALS should reflect the ultimate purposes of those who have both direct and indirect interests in the project.

example: to produce safe effluent water that protects human health and the environment

OBJECTIVES specify which characteristics of the system are to be optimized in order to achieve the goals. Things such as cost, aesthetics, etc.

ecample: maximize the safety of the plant

2. Then specify the criteria against which you will measure how well the goals/objectives are met

CONSTRAINTS: drive the alternatives selection and design by mandating limits that cannot be exceeded

these MAY be legal limits

examples: must fit the WWRF on the available land

must comply with NPDES permit limits from the state

must comply with water rights

maximum amount of money (potentially)

CRITERIA: are desirable or undesirable elements against which the design will be judged;

a set of parameters used to measure how optimum a solution is with respect to the objectives

Criteria are subject to interpretation !

As the design team you need to balance your professional judgement with both the Client concerns and public concerns.

Non-technical issues have a large impact on the final design

social, economic, & political issues should be considered

Frequently, the goals, objectives, and criteria may conflict; therefore, it is important to rank the relative importance of each. Example: optimal water quality vs low cost

How well each alternative satisfies a criteria is frequently a subjective judgement, since it doesn’t involve quantifiable elements

Due to the complexity of our problem, and the HUGE range of possible combinations of processes to achieve our goals, your team will likely need to “discretize” the problems.

Example A

1. primary treatment of all WW flow

2. secondary treatment of all WW flow

3. advanced treatment of all WW flow

for next 5 years, remove ammonia

in 10 to 15 yrs, need to remove N

in 15 to 20 yrs, need to remove P

Example B

1. meet Q and effluent limits for next 5 years

2. meet Q and effluent limits for 5-15 yrs

3. meet Q and effluent limits for 15-20 yrs

Example C

1. remove solids

2. remove BOD

3. remove bacteria

4. remove ammonia

5. remove N & P (for reuse, or in 15-20 yrs)

6. treat biosolids

Example D: unit processes

1. primary settlers

2. activated sludge

3. biotrickling filters

etc.....

** first cut: eliminate things that don’t meet CONSTRAINTS

** next: primary criteria? main criteria with sub-criteria?

-> try to narrow to 3 to 5 options for detailed evaluation (1/person)

** listing the criteria is not enough -- need to include a sentence or 2 definition, so that everyone will interpret each criteria the same

COMMUNICATION IS VITAL TO DEFINE AND WEIGHT DESIGN OBJECTIVES

1. NORMAL

1. EXTERNAL - design engineers with clients, stakeholders

* meetings & presentations

* town meetings with presentations & Q/A

* workshops (1-2 days)

- written via surveys, letters, e-mail

2. INTERNAL - within design firm or team

* brainstorming

* informal presentations

* exchange written proposal, sketches, calcs

* circulate among whole team

2. CONFLICT RESOLUTION

1. EXTERNAL

- due to miscommunication

(most conflict can be avoided by good, open communication)

- client or engineer making criteria into constraints

(not enough flexibility)

- ethical

- may require a 3rd party mediator to resolve

DECISION MATRIX AN EFFECTIVE TOOL TO COMPARE & PRESENT RESULTS

CAN RUN A COST:BENEFIT ANALYSIS FOR EACH ALTERNATIVE; PICK ALTERNATIVE WITH HIGHEST B/C RATIO

Examples of constraints and criteria applicable for wastewater treatment plants