environmental engineering

strategic environmental assessment

required by european directive2001/42/EC — add in earliest point to stich in environmental protection (plans & programmes, even jobs located, county development plan etc. is the environmental capacity ) SYSTEMATIC, PREDICTION, MONITOR

BOD biochemical oxygen demand

Amount of oxygen utilized by microorganisms in oxidizing (degrading) carbonaceous and nitrogenous organic matter

Measured strength of water / waste water

Dissolved Oxygen

At any give temperature and pressure water can contain some maximum concentration of dissolved oxygen determine through Henry’s law

environmental risk

hazard is not the same as risk (hazard has potential to cause harm, risk is likelihood of harm in defined circumstances) —→ environmental risk could include waste, emissions, resource depletion

environmental justice case

EIA

class of development may or may not require, but it must be screened, (Screeening PROCESS) —→ can consider mitigation

how to limit risk

risk = f(hazard, exposure) reduce exposure to hazard but if those fail risk is a function of hazard, develop solutions using less hazardous components

four components of risk assessment

1. hazard assessment 2. dose-response assessment 3. exposure assessment 4. risk characterisation

what does risk assessment seek to answer

chemicals/substance present —- problems chemicals cause ——probability of adverse affect post exposure —- severe

hazard assessment includes

whether chemical is linked to particular health concern —> review and analyse toxicity data, weigh evidence of toxic effects, evaluate toxic effects in one situation occur in other

dose-response assessment —-if an adult male, weighing 70 kg, drinks a glass of water contaminated with 0.015 mg/L of lead, what
is the dose? Assume he drinks 2L/day

(0.015 mg/L x 2 L/day) / 70 kg = 4.3 x10-4 mg/kg-day = 0.4 μg/kg-day

carcinogens no threshold, noncarcinogenic threshold so there is a NOAEL (no observable adverse effect) and reference dose based on that and safety factor

EIAR

prepared by DEVELOPER —-description of project, signifcant effects, non-technical summary etc (detailed description of project)

exposure assessment

EXTENT FREQUENCY sources chemical —pathway to exposure — how much people exposed to —how often people exposed —some people more at risk

risk characterisation CARCINOGENS

ACCEPTABLE LEVEL — from three other steps —- Risk = dose * risk per unit dose think about exposure

EIA

PROCESS (by competent authority)

screening —> scoping —> EIA report —> consultation —→ evaluation —> decision —> monitoring

risk characterisation NON-CARCINOGENS

Non carcinogens have a threshold dose. Acceptable risk is determined by calculating a hazard
quotient (HQ). This is evaluated by comparing the daily intake with the reference dose:
HQ = average daily dose / RfD (reference dose)
If HQ ≤ 1 , then there is no adverse risk.
If HQ > 1, then there is a possibility of an adverse impact

marginal analysis

cost-benefit analysis

SWOT DIAGRAM

INTERNAL about achieving objects (strengths & weaknesses ) EXTERNAL situations (opportunities & threats)

decision matrix

list of pros/cons with level of importance to each factor (lists relevant parameters/criteria/factors ) weights importance of factor to decision, lists decision alternatives and the value

pareto analysis

statistical technique (uses pareto principle or 80.20 rule) identify significant aspects problem to focus effort (plot bars based on use such as water use which causes most focus on those with the line adding each value)

POROUS MEDIA FLOW —> An aquifer has been contaminated by a leaking underground storage tank at a petrol station. A well that serves as the drinking water supply for a small village is 200 m down-gradient of the petrol station. Tests on the aquifer have shown it to have a porosity of 39% and a hydraulic conductivity of 45 m/d. How long will it take for the contamination to reach the village well if the
hydraulic gradient is 40 cm over the 200 m?
• What is the Darcian velocity (vd)? [Hint: Q = - k A (dh / dx)]
• What is the true velocity (vtrue)?
• Can you calculate time required for the contamination to reach the village well, based on the distance it has to travel and the true velocity?

First find the Darcian velocity, vd —> Q = - k A (dh / dx)
Q / A = vd = - k (dh / dx) vd = -45 m d-1(- 0.4 m / 200 m)= 0.09 m d-1 ——> True velocity (vtrue) > vd vtrue = (1 / η ) vd vtrue
= (1 / 0.39)(0.09 m d-1) = 0.23 m d-1 —→ Thus for the contamination to travel 200 m, it will take
t = 200 m / 0.23 m d-1 = 869 d = 2.4 years

appropriate assessment

protect habitats & species (EIA more general)

STOKES Grit is a common element in raw municipal wastewater and must be removed so that it does not damage machinery in the plant, e.g. pumps. Removal can take place by gravity settling. If the smallest particles to be removed have diameter, DP = 100 μm and a density of 2.65 g/cm3, how fast will they settle? If water has a viscosity of 0.01185 g/cm-1s-1 and a density of 1 g/cm3. Use Stokes’ law vs = g [(ρp – ρf ) / 18μ] * Dp2

Apply the Stoke’s law formula here:
vs = g [(ρp – ρf ) / 18μ] Dp2 = [(980 cm s-2 (2.65 g cm-3 – 1 g cm-3)) / (18 (0.01185 g cm-1s-1)] * (100 X 10-4cm)2 = 0.76 cm s-1 (27 m h-1)

theoretical oxygen demand

oxygen required to oxidize organic pollutants

ADJECTIVE FLUX A municipal wastewater effluent is discharged into a river. The effluent contains 5 mg P/l and is discharged at the rate of 1 m3/s. Upstream of the discharge, the river contains a background concentration of 0.01 mg P/l and flows at a volumetric rate of 25 m3/s. What is the flux density of P downstream of the effluent discharge if the river has a cross-sectional area
of 30 m2?
• How will you construct the materials balance equation in this case?
• What is the concentration of Phosphorus (mg P/l) downstream?
• What is the average velocity of flow (m/s) downstream?

Qmix = Q1 + Q2
Qmix Cmix = Q1C1 + Q2 C2
Cmix = ((Q1C1) + (Q2C2 )) / (Q1 + Q2)
Substitute values and calculate for Cmix
Cmix = ((25 0.01) + (1 * 5 )) / (25 + 1) = 0.20 mg L-1
vave = Qmix / A = [(25 +1)] / 30 = 0.87 m s-1

avection

bulk transport with fluid — material moves with mean fluid flow

dispersion

movement by random motion within a fluid 1. molecular is strictly random motion of molecules 2. turbulent is random motion of fluid in mass transport

plug flow reactor

no mixing assumed before after plug - that it is advective transport (actually gaussian distribution)

stoke’s law

calculates terminal velocity of a particle settling in a fluid where terminal velocity is the constant max velocity a particle reaches when falling through a fluid so Fg-Fb-Fd = 0)

horizontal flow grit chamber

provide hydraluic residence time long enough for desired particles to settle specific depth, h, design depth

primary clarifier vs grit chamber

primary clarify removes through gravity settling —- grit chamber removes debris like ragging of clogging and usually spins in reactor (stokes low in horizontal flow or aeration helical flow pattern)

hydraulic gradient

rate of loss of energy due to friction delta h / delta x in porous media flow

darcy’s law

k is the hydraulic conductivity in m/d

streer-phelps equation

predicts the dissolved oxygen changes in water over time after introduction of a biodegradable substance into an aquatic environment

t is the time for water to travel a distance x downstream (t=x/U river velocity)

if DO is taken as water quality parameter, streeter-phelps equation can provide relationship between water quality standards and effluent standards

deoxygenation coefficient k1

calculated to give the best fit to BOD data

characteristic of particular waste

affected by temperature

affects relative easy with which waste or waste water is degraded

affects the rate of oxygen demand, but not the ultimate demand

reaeration rate k2

characteristic of surface water

waters with swift movement and turbulence have higher k2

aral sea

saline lake - diverted to irrigate desert water level drop and salinity rose, soil eroison, dust storms.

what do engineers design for

robustness, adaptability, resilience

last for long term (sustainable) respond to threats (resilience)

main source of NOx in Ireland

traffic emissions

contributes to ground level ozone and acid rain

PM 10 & PM 2.5 in Ireland in relation to WHO guidelines

both above

Polycyclic aromatic hydrocarbons (PAHs)

can impact water quality

organic compounds from burning

the overall AQIH

highest of five pollutant indices (ozon, nitrogen, sulphur, PM 2.5, PM 10)

We know the hourly mean value (for the EU directive) for ozone (O3) is limited to a daily average of 120 μg/m3, but our sensor measures the concentration of O3 in ppb.

What is the concentration in μg/m3 for a concentration of O3 of 80 ppbv, assuming the temperature is 21oC and pressure is 1 atm.

Is it below the EU limit?
What is the concentration in μg/m3 for a concentration of O3 of 80 ppbv?

1. calculate volume ratio from concentration value oxygen to air

2. use ideal gas law to get n = V X (P/RT)

3. use molecular weight to convert moles to mass

EU limit is 120

advection

when molecules move in bulk with mean fluid flow

plug flow

dispersion

random motion within a fluid

eliminates dramatic concentration gradients

EU treaties

• the objectives of the european union,

• the rules for EU institutions, how decisions are made and

• the relationship between the EU and its member countries.

stokes law

determines terminal velocity

darcy law

• flow rate through porous media proportional to head loss and inversely proportional to length flow path

dh/dx is hydraulic gradient with dh as the loss of energy due to friction

available volume for flow, velocity, true velocity

water framework directive

BOD, chemical status, physico-chemical, hydromorphological

agreed by all EU member states in 2000

implemented as 6 yr cycle in 2009

catchment for recharge zone in an unconfined aquifer

hyetograph

graph of intensity (mm/hr) vs time

depth-duration-frequency analyses

polluter pays principle

• someone is financially responsible for elimination of pollution they cause

• customers pay for their own bag or bring one

precautionary principle

• must take a precautionary approach (policy makers) in situations of uncertain damage

proximity principle

• waste should be managed as close to source of creation as possible

regulations

• legal acts that apply automatically and uniformly to all eu countries as soon as they enter into force, without needing to be transposed into national law.

• They are binding in their entirety on all EU countries.

directives

require EU countries to achieve a certain result, but leave them free to choose how to do so.

• bathing water directive

  • must monitor at least two parameters of faecal bateria

  • must inform public about bathing quality

should

• do every year

• four samples per season

• at the end of every season

• prepare description

decisions

are binding to those whom which it is specified / addressed to (only).

recommendations

• EU institutions to make their views known

• to suggest a line of action without imposing any legal obligation on those to whom it is addressed.

• They have no binding force.

opinions

allow institutions to make a statement, without imposing legal obligation.