NCEES PE Agricultural and Biological Engineering Agricultural Waste Management & Environmental Engineering: practice questions

1 · Basics of wastewater treatment · hard

An activated sludge plant treating sugar-rich food wastewater develops an SVI above 250 mL/g with a cloudy, slow-settling sludge. Which combination is most likely to cause this?

1. Very high dissolved oxygen together with a short sludge age of one day
2. Over-wasting of sludge that lowered the MLSS well below the design value
3. Excess nitrogen and phosphorus added at well above the BOD:N:P need
4. Filamentous growth favoured by low dissolved oxygen and nutrient shortage

2 · Anaerobic lagoons · medium

Anaerobic lagoons are built relatively deep compared with facultative ponds mainly because depth:

1. Removes the need for any liner in permeable soils
2. Allows wind action to mix oxygen into the bottom sludge layer
3. Increases surface area, which raises algal oxygen production
4. Reduces surface area, lowering odour release and heat loss

3 · Composting · hard

Leaves (C 45%, N 1.0%, dry) are mixed with poultry litter (C 35%, N 3.5%, dry). For a starting C:N of 25:1, the dry mass of leaves per kg of dry litter is:

1. 0.38 kg
2. 1.00 kg
3. 2.63 kg
4. 0.75 kg

4 · Composting · medium

A windrow of food waste and manure at 75% moisture turns grey, slumps and smells of rotten eggs. The best corrective action is to:

1. Add water to cool the pile and stop the odour
2. Cover the pile tightly with plastic sheet to trap the odour
3. Add urea to raise the nitrogen content of the mix
4. Blend in a dry bulking agent and turn to restore air space

5 · Composting · medium

Which observation best indicates that compost has become stable and mature?

1. A C:N ratio that has risen well above that of the starting mix
2. Low respiration rate and no reheating after the pile is turned
3. A core temperature that rises again to 60 °C after turning
4. A strong ammonia smell when the pile is opened and turned

6 · Manure handling systems · medium

A dairy of 200 cows produces manure and wash water at 0.06 m³ per cow per day. For a 180-day storage period, the manure and wastewater component of storage volume (excluding rain, sludge and freeboard) is:

1. 2,160 m³
2. 21,600 m³
3. 216 m³
4. 12 m³

7 · Nutrient management plans · easy

The '4R' framework of nutrient stewardship refers to the right:

1. Soil, rainfall, tillage and yield
2. Nitrogen, phosphorus, potassium and sulphur
3. Source, rate, time and place
4. Crop, cost, labour and machine

8 · Environmental impact assessment · medium

An engineer preparing an EIA for a new distillery in one country uses the project category thresholds from another country's rules. This is wrong because:

1. Thresholds apply only to private projects and never to distilleries
2. Categories, thresholds and procedures are set nationally and are revised
3. Distilleries are exempt from EIA under every international convention
4. All countries use the same thresholds, so a foreign text is out of date

9 · Air quality and odour · hard

A pig unit gets odour complaints from houses 400 m downwind in summer evenings. Which combination addresses the source rather than only the pathway?

1. Adding masking fragrance to the exhaust air on summer evenings
2. Lower dietary crude protein, frequent manure removal and a covered slurry store
3. Planting a tall tree belt between the unit and the nearest houses, and nothing else
4. Moving the houses or buying the land to increase separation

10 · Manure handling systems · hard

A slurry has 8% total solids, 2.0 kg/m³ of P and 4.0 kg/m³ of ammonium-N. A separator captures 60% of solids, 50% of P and 10% of ammonium in the solid fraction. For the liquid fraction, the ratio of ammonium-N to P compared with the raw slurry is:

1. 0.6 times higher
2. 1.0 times higher
3. 1.8 times higher
4. 3.6 times higher