Wastewater Final Exam

What are the five components of an onsite wastewater system, and what function(s) does each
component serve?

Septic tank- Wastewater stratified, liquid effluent exits tank, solids remain

Distribution box- Send liquid effluent to drainfield trench

Drainfield trench- Holds liquids until infiltrates into soil

Soil beneath trench- Aerobic bacteria eats away at pathogens

Setbacks- Must be a horizontal slope to distance from property lines

List 2 principles of pretreatment by septic tanks

Solid separation and retention time

What are some typical concentrations of total nitrogen (mg/L), total phosphorus (mg/L), and
BOD5 (mg/L) for 1) septic tank effluent and 2) septage?

Effluent TN:60 mg/l

Septage TN:588mg/l

Effluent BOD:250mg/l

Septage BOD:6480mg/l

Effluent TP:10mg/l

Septage TP:210

If wastewater is not properly treated and disposed, what water quality problems may arise

Waterborne diseases, algae blooms, dissolved oxygen depletion, ocean/shellfish water closures due to high concentrations of bacteria

Why is it important to have septic tanks pumped

So they aren’t over used potentially causing effluent to rise to surface or septic failure

What are 2 common methods of septage application

Tank truck, injection from tank wagon, semi-solid material spreading, direct injection

What is typically added to septage before land disposal

lime treatment

What is the difference between volatile and fixed solids

Volatile-Portion that is heated to 550C, Fixed- Portion that remains after sample is heated.

What is the difference between dissolved and suspended solids

Suspended-Part of sample that doesnt pass through 0.45um filter

Dissolved- Part of sample that passes through filter

What are FOGS and how can they influence septic system performance

Fats, Oils, Greases. They may disrupt decomposition of waste material potentially causing septic system failure.

List 3 things required in the report to obtain a permit to apply septage to a field? Who must write the report

A licenssed soil scientist or professional geologist must write the report.

1. Location of site, 2. Written signed authorization of septage land for all land owners, 3. Types of septage, proposed annual volume for land per acre.

List the 5 principles of onsite wastewater treatment

1. Ensure effluent doesn’t come to surface

2. Maximize aerobic treatment beneath drainfield trenches

3. Apply effluent only to soil in suitable and prepared treatment disposal field

4. Distribution box doesn’t leak

   1. Drainfield trenches are at setbacks, at slope where effluent is distributed evenly and leveled

What is BOD

Biochemical Oxygen Demand

What is the biomat and name one positive and one negative aspect of biomat formation

Biomat-An active layer of organic matter that covers the bottom and sides of the tank

Positive-Improves treatment by preventing groundwater contamination

Negative- May cause hydraulic

If effluent surfaces in a yard, why is it a concern?

Potential contact with pathogens, vectors can transmit diseases associated with pathogens

List three potential negative issues with land application of septage.

Odor, public health pathogens, perception

List 2 reasons why wastewater management is an important subject to study and understand

To understand and educate on wastewater to prevent groundwater, ocean, lake, river, etc contamination

To learn how wastewater should be properly managed for public health

Define water use impairment and list 3 pollutants commonly associated with water use impairment

Water that is impaired by contamination and cannot be used.

Bacteria, sediment, turbidity

List 2 examples of indicator bacteria that are used to assess water quality conditions

E.coli, Enterococcus

Why are long, narrow septic system trenches preferred over wider, short trenches?

more wastewater/ soil contact area

What coastal environmental problems may be partly linked to wastewater management (other
factors, but wastewater can contribute also)?

Eutrophication, shellfish water closures, swimming advisories

On average, how much water does each person use per day?

60 g/d

What is the difference between pollutant concentrations and pollutant loadings?

Concentration=mass/volume

Loadings=mass/time, concentration*discharge

How does the concentration of organic matter in water affect dissolved oxygen?

The higher the organic matter the lower the dissolved oxygen

How does temperature affect dissolved oxygen?

The higher the temp the lower the dossilved oxygen

If most E. coli and fecal coliform bacteria are not harmful to humans, why do we test for them
and get concerned if they are found in the water samples?

indicator bacteria, other pathogens may be present

How does the speciation of nitrogen (form) affect it’s mobility in soil (NO3 in comparison to
NH4)?

NO3 is generally more mobile because it is an anion and most soils have a negative charge
b. NH4 is not as mobile because it is a cation

What forms of nitrogen are dominant in septic tanks?

Organic N, NH3, NH4

List three factors for determining where septage can be land applied.

Soil type, setbacks, slope

What are the soil depth requirements to apply septage on fields with group I, II and III soils?

Group 1: 36 inches

Group 2: 24 inches

Group 3: 18

What are the setback requirements for septage application sites and property lines, occupied homes, and streams?

Property line : 50ft, Homes: 500 ft. Streams 200-300 ft

List 3 designated water resource uses

Water supply, recreation, aquatic habitat

How many onsite systems are in use in NC? How many new systems are installed each year in NC? How many systems are repaired each year in NC?

2 million. 24,000 installed, 6,200 repaired

Which component of an onsite system is most important for wastewater treatment?

Soil

How much aerated soil is required beneath septic system drainfield trenches in group 1 soils and how much beneath group 3-4 soils? Why are there different requirements

Group 1:18 inches

Group 2-4: 12 inches

In group 1, water moves through sand much quicker, it has a higher saturation rate

What does LTAR stand for

Long Term Acceptance Rate

List 3 examples of media used for wastewater storage in drainfield trenches

Polystyrene aggregate, Tire chips, Diameter pipe

What are the minimum soil depth requirements for these systems: Polystyrene aggregate, Low profile chamber, LLP, Mound/fill, Block Panel

Polystyrene: 24 inches

Low profile chamber: 20 inches

LLP: 20 inches

Mound/fill: 18 for suitable soils, 12 for water table

Block Panel: 27 inches

List examples of physical, chemical, and biological treatment processes that may occur in soil beneath drainfield trenches

Physical: Filtration, dilution

Chemical: Precipitation, Adsorption

Biological: Nitrofication, oxidation

What is the difference between serial and equal distribution

Serial-Releases wastewater into one trench at a time (Drop box, step down)

Equal- Releases the same amount of wastewater into each trench (distribution box)

What is the difference between an LLP and a pump to conventional system

An LLP requires a certified operator to maintain the system for the life of the system

How do % slope and trench width affect the required soil depth for an onsite wastewater system on a lot that is not flat

As the slope and trench width increases, the soil depth requirements increase

List the components of a septic tank and describe function

Baffle wall: Slows the flow of wastewater

Sanitary T: Prevents large solids from leaving tank

Inlet pipe: Where wastewater enters the tank

Free board: Space that allows storage for surges of wastewater

Manholes: Provides access to pump tank and clean filters

Outlet: Where wastewater leaves the tank

How can you test to ensure that a septic tank is watertight

Vaccuum test and hydrostatic water test

List 2 reasons for excessive clogging of the effluent screen

High FOGS in wastewater, high peak flows, extensive hair/lint

Describe why effective volume of a septic tank may decrease over time

Effective volume is the liquid capacity, over time liquids are absorbed or leaves the tank, decreasing over time

Why is spreading out laundry days an important septic system maintenance recomendation

To prevent an overflow of wastewater to the system, water needs sufficient time to filtrate

If a septic system has 4 drainfield trenches, and one of the trenches is very wet and soggy and the others are dry, what may cause this issue and how can it be resolved

Wastewater is only or mainly going to one trench, adjusting the dial to allow the flow of wastewater to go to other trenches

How do environmental professionals determine a wetness condition by looking at soil

Low chroma colors, gray mottles

The consistence of expansive clays are described as

Very firm, very sticky, very plastic

Why is it important to ensure that drainfield trenches are installed level

For proper water treatment and system longevity

Why do some gravel-less technologies allow system designers to reduce the drainfield area requirements by 25% in relation to gravel systems

They have greater storage capacity than gravel systems

What is the benefit of a bed system, if you have to increase the disposal area by 50% in relation to a trench system

Reduce the total area, there will be no space between trenches

Why is there a different requirement for Group 1 and Group 3 soils

Group 1: 18 inches

Group 3: 12 inches

They need sufficient residence time for treatment, Ksat is really high in G1

List 3 effluent distribution devices

Distribution box, Drop box, Step down

List 5 soil and site evaluation factors used for determining if a property is suitable for a septic system

Soil texture, soil structure, soil depth, soil color, soil wetness, soil minerology

Landscape position, slope, available space, organic soils, restrictive horizons

Explain how curtain drain may improve the functionality of an onsite system

Helps prevent subsurface, laterally moving water from flooding drainfield

List 2 materials typically used to construct septic tanks, what material is most common

Concrete, fiberglass, polyethylene. Concrete is most common

List 3 factors that can anaerobic digestion in septic tanks

pH extremes, chemicals, lack of maintenance

Which parts of a septic tank are most likely to leak

Joints (mid seam or top), inlet and outle pipe penetrations, access/riser lid joint, weep holes at the base of the tank, any location that is damaged

What information should be imprinted on each septic tank

Tank manufacturer, serial number, liquid capacity, and date the tank was made

What is the difference between rated and effective volumes of septic tanks

Rated volume- Total capacity of solids and liquids

Effective volumes- Liquid capacity, less than rated, just after the tank is pumped or before first use

List 4 septic system maintenance recommendations for improving the longevity of the system

Avoid simultaneous discharges, keep non sewage out of the system, dont flush cigarette butts, avoid consecutive laundry loads

List 3 gases that are typically produced in septic tanks as organic matter is digested anaerobically

CO2, CH4, NH3

What is the recommended detention time of wastewater in a septic tank

1 to 2 days

Why do new septic tanks have 2 access manholes

There is a baffle wall and both sides of the wall have to be pumped

What device is typically used in distribution boxes to ensure equal distribution to the drainfield trenches

Flow leveling device

Why are LLP onsite systems typically more expensive to maintain than a pump to conventional system

They require a certified operator to main the system for the life of the system

How can you tell the difference between a distribution box and a drop box

Distribution box pipes are laid level

Drop box, one header pipe is higher than others, allowing the uppermost trench to fill first

List the 5 soil forming factors

Parent material, climate, organisms, time, relief

LEO sat GER means what

Loss of electrons is oxidation, Gain of electrons is reduction

What is the difference between a relict feature and a lithochromic feature

Relict feautre-Occurs when soil colors aren’t at equilibrium with conditions (Drainage)

Lithochromic feature- Inherits its color from parent material (dune sand from low iron content

If a landowner believes their property has a lower seasonal high water table than was predicted based on the soil and site evaluation, then what option does the landowner have to appeal that decision

The owner can hire a consultant to monitor groundwater levels over the proposed drainfield area during the wet season to get an accurate measure of groundwater level

What are 2 unsuitable landscape positions for septic systems

wetlands, depressions

How do environmental health specialists typically determine the depth of the seasonal highwater table during soil/site evaluations

Soil borings, observation of redox features

How does compaction influence bulk density? how would compaction influence wastewater percolation infiltration rates

Compaction increases bulk density

Compaction reduces wastewater percolation

What method is used in the field to estimate soil texture

Texture by feel, Lab method: Hydrometer

Why is it important that field estimates of the depth to the seasonal high water table are accurate in regards to permitting onsite wastewater systems

So groundwater will not be contaminated. Gives wastewater enough time and space to be treated by soil before coming into contact with groundwater

Which soil particle has the lowest surface area per given mass

Sand

List 2 examples of soil structure that are unsuitable for onsite wastewater systems

Massive, platy

How can you tell in the field if a soil sample has expansive clay

Very sticky, very firm, and very plastic

External drainage is controlled by __ while internal drainage is controlled by

topography; soil properties

Upslope areas have good external drainage, while downslope areas have __ external drainage 

poor

Sites with a slope that exceeds __ are always classified as unsuitable

65%

In the coastal plain, some of the areas with poorly drained soils are located in areas with large distances between streams, also called

Interstream divides

How can understanding groundwater flow direction be useful in designing the layout of a drainfield if you want to maximize dilution and dispersion?

Understanding groundwater flow direction can be useful to design the layout of a drain field in the direction of the groundwater flow direction in order to maximize dilution and dispersion. 

List 2 sources of topographic data 

Terrain Navigator Pro, USGS quadrangles 

List 3 media that may be used in trickling filters for centralized sewer treatment

gravel, molded plastic, bricks

List three examples of media types used in media filters for onsite wastewater treatment?

peat, sand, hard plastic

Why is it beneficial to have wastewater applied in small doses to the media filters?

To ensure aeration and unsaturated flow

List 4 modes of treatment provided by media filters and explain the processes?

Filtration and trapping- Larger particles filtered by small pore openings, unsaturated flow

Adsorption- Organisms, cations, bound to surfaces of media

Biological decomposition- Breakdown of organic matter into simpler products

Biochemical transformation- Nitrification, denitrification

Why do the NO3 concentrations increase as wastewater moves through a media filter?

Nitrification of NH4, aerated conditions

What % reduction in BOD and TSS do media filters for septic systems typically provide?

Greater than 90%

Effluent from media filters can be surface discharged if it is _____________?

Disinfected

How do media filters affect the formation of biomats at the soil/trench interface?

Reduce biomat formation, remove BOD, TSS, and provide cleaner effleunt that is discharged into the soil

List three examples of situations when media filters are typically used?

Environmentally sensitive areas, areas with limited soil depth, larger flows/smaller areas

What are some important sand filter design parameters?

single pass or recirculating, free access or buried, media specifications

What are the two major categories of media filters?

Single pass and recirculating

What are some benefits of pressure-dosed sand filters in relation to gravity flow sand filters?

longer life span of media, pump control to allow effluent to be dispersed equally over time and space, more even distribution of effluent promotes unsaturated flow

How does media size influence sand filter treatment and disposal?

Smaller media= more surface area=better treatment, but slower water movement and disposal