Planning for Cost Effective Waste Water Management

1
Planning for Cost Effective Waste Water Management

• Alec Fleming,
• County Manager,
• Clare County Council

2
Approach to Recycling

• Use of agricultural slurry as a fertiliser
  accounts for the majority of recycling.
• Municipal sludges can be used as agricultural
  fertiliser after dewatering and an appropriate
  pasteurisation process.
• Industrial sludges are generally not suitable for
  recycling.

3
Biological Options

• Rotating Percolating filters are the oldest form
  of treatment unit consisting of a bed of stone,
  circular or rectangular in shape with
  intermittent or continuous addition of settled
  sewage to the surface. Biotowers are a variant of
  the Rotating Percolating filters but use plastic
  media to achieve a higher hydraulic and organic
  load.

4
Biological Options (contd.)

• Rotating Biological Contactors comprise a
  cylinder rotating on its horizontal axis. The
  cylinder is made from high-density plastic. This
  process was generally used on small installations
  throughout the country.

5
Biological Options (contd.)

• What are we trying to achieve?
• (a) Reduce suspended solids.
• (b) Reduce organic load (BOD).
• (c) Remove phosphorous.
• (d) Remove nitrogen.

6
Biological Options (contd.)

• Secondary treatment together with constructed
  wetlands technology is a low running cost option
  for small rural treatment plants in sensitive
  areas. The downside is that they have a large
  land take requirement which in recent years was
  almost prohibitive due to land costs.
• Biodegradation is the dominant mechanism of
  organic removal for municipal and most waste
  waters. Most large municipal treatment systems
  now use activated sludge systems for the purpose
  of organics removal.

7
Biological Options (contd.)

• Nitrogen and Phosphorous removal may also be
  carried out by biological processes. In the case
  of nitrogen the process is denitrification
  followed by oxidation and nitrification.
  Phosphorous removal is a two stage biological
  process and can achieve removal rates of up
  70-80.

8
Developing Cost Effective Processes

• Accurate forecasting of future needs is an
  essential pre-requisite to cost effective
  processes. Modular development of treatment
  systems and networks to match the demands will
  give cost effective solutions. It is easier to
  achieve cost effective solutions in periods of
  expansion, with certainty of demand requirements
  and limited scale.

9
Developing Cost Effective Processes (contd.)

• In large public authority projects, the planning
  period from assessment of needs to delivery of
  systems, a period of ten years or more in certain
  cases, difficulties arise in development of cost
  effective solutions.

10
Developing Cost Effective Processes (contd.)

• Cost Benefit Analysis if adapted to include
  sustainability and the principle of safe minimum
  standards plus the use of the modular approach
  can be the best method of achieving cost
  effective processes.

11
Capital Expenditure

• Capital expenditure is the funding mechanism by
  which all public capital project are put in
  place. At the earliest possible opportunity, once
  a Feasibility Report has been prepared, project
  appraisal in the form of a Cost Benefit Analysis
  should be carried out. Sustainability and the
  principle of minimum standards should be included
  as principles in the Cost Benefit Analysis.

12
Capital Expenditure (contd.)

• The Water Services Investment Programme is funded
  by Capital Grants provided by the DEHLG and Local
  Authority Funds. Local authority funds are
  provided from planning contributions and loans
  raised from banking institutions. Any loans
  raised are subject to approval of the elected
  members in the first instance and later by the
  DEHLG.

13
Capital Expenditure (contd.)

• The process of loan approval by the DEHLG is a
  long process and as the local authority borrowing
  limit is set in the context of General Government
  Balance to ensure all borrowing is maintained
  within the limits of the Growth and Stability
  Pact.

14
Waste to Energy Recovery

• It has been known for a considerable period of
  time that sludge, derived from municipal
  wastewater treatment plants, has economic
  benefits. Municipal sludge has a considerable
  calorific value and the method of abstracting
  this value remains an issue for resolution. In
  large waste water treatment plants anaerobic
  digestion resulting in the production of methane
  gas is the preferred and economic solution.

15
Waste to Energy Recovery (contd.)

• Anaerobic Digestion has the advantage of
  producing methane gas which can be utilised as
  part of the energy requirement of the waste water
  treatment plant installation. Anaerobic Digestion
  also reduces the sludge in volume by 30-50 and
  sludge is rendered odour and pathogen free as an
  end product.
• Stabilised sludge is also capable of utilisation
  as a fuel for power station or cement factories,
  where burning at high temperatures takes place.

16
SUDS

• Sustainable Urban Drainage Systems (SUDS) has
  developed as a system to attenuate rainfall
  discharge, especially in times of persistent or
  heavy rainfall, to receiving pipe systems,
  streams, rivers lakes or aquifer recharge. SUDS
  is a system that focuses decisions about drainage
  on the environment and people.

17
SUDS (contd.)

• In SUD systems decisions will take account of
  drainage and the effect of such drainage on water
  quality, water quantity, amenity and people.
  Properly designed SUD systems will incorporate
  swales, storage facilities either in tanks,
  ponds, lakes, pipes or proprietary storage
  systems with high voids ratios plus filtering
  systems using natural vegetation/soil/ gravel/
  geotextile combinations to reduce the amount of
  pollutants being discharged to receiving waters.

18
SUDS (contd.)

• Local authorities across the country incorporate
  conditions relating to SUDS in planning
  permissions issued, depending on the local
  conditions relating to the application. Such
  conditions may restrict discharge flows at
  certain times.

19
Treatment

• Effective sewage treatment comprises screening,
  grit removal, primary settlement, oxidation ,
  secondary clarification, sludge treatment and
  disposal and discharge of treated effluent to the
  receiving water in accordance with the licence
  issued by the EPA under the Waste Water Discharge
  (Authorisation) Regulations 2007.

20
Treatment (contd.)

• The number and combination of processes required
  to meet the final treatment standards processes
  depend on the condition of the effluent
  generated, the availability, quality, type and
  volume of the receiving water, the availability
  of suitable land and the Licence conditions
  imposed by the EPA under their new powers.

21
Monitoring

• Recent Waste Water Discharge Licence issued by
  the EPA requires the following parameters to be
  monitored on the primary secondary discharge
• pH, BOD, COD, Suspended Solids, Total
  Nitrogen, Total Phosphorus, Ammonia,
• Oils, Fats Grease, Temperature, Toxicity,
  Metals Organic compounds.

22
Implementation of Standards

• Treatment standards for waste water treatment
  plants are set by EU directives transposed into
  Irish law. The Urban Waste Water Regulations
  gives standards for Biological Oxygen Demand
  (BOD), Suspended Solids (SS), Chemical Oxygen
  Demand (COD), Phosphorous and Nitrogen .

23
Implementation of Standards (contd.)

• However depending on the receiving waters type
  and the presence of European designated sites,
  e.g. (SPA, NHA, SAC), other regulations apply to
  treatment standards also, such as Dangerous
  Substances Regulations, Water Frame Regulations
  (relevant pollutants), Bathing Water Regulations,
  Birds Directive, Habitats Directive, Live
  Molluscs (Production Areas) Designation 2006,
  etc.

24
Implementation of Standards (contd.)

• The Waste Water Discharge (Authorisation)
  Regulations 2007, which require local authorities
  to apply to the EPA to licence waste water
  discharges to receiving waters over the period up
  to June 2009 and compliance with these licence
  conditions will ensure implementation of these
  standards.

25
Climate Change

• Climate change in Ireland is the subject of
  ongoing research being carried out by Met Eireann
  under a project called Community Climate Change
  Ireland. This project is examining climate change
  under a number of headings, Influence of the
  Atlantic Ocean, Storms, Uncertainty, River
  Flooding, Health, Agriculture and Economics.

26
Climate Change (contd.)

• Since 1993 observed increases in sea level rises
  vary from 2.3 to 4.7 mm per year. Rising and
  warming seas will increase the frequency and
  severity of storms and cyclones with very high
  wind speeds.

27
Climate Change (contd.)

• It must be acknowledged that climate modelling is
  an inexact science and computer models are not
  perfect but increasingly are embracing the many
  interlocking factors contributing to climate
  change.

28
Climate Change (contd.)

• River flooding, in August this year, has reminded
  people of the devastation caused to crops,
  property and life by unexpected and usual levels
  of summer rainfall. Overall the expectation is
  that Ireland will experience increased winter
  precipitation with a rise of winter river flows
  while in summer increased temperatures and
  decreased precipitation will cause a reduction in
  summer river flows.

29
Climate Change (contd.)

• Water supply management and design plus drainage
  solutions must be re-assessed with the changing
  weather patterns.

30
Climate Change (contd.)

• Health is affected by the depletion of the ozone
  layer while agriculture may be further affected
  by pests and disease currently not present in
  Ireland. The major benefit to Ireland from
  climate change is decreasing fuel bills for
  domestic heating in winter and spring time.