John Cocks, MWH NZ Robert van Bentum, MWH NZ Presenter

Transcription

1 John Cocks, MWH NZ Robert van Bentum, MWH NZ Presenter

2 Goal of Sustainable Sanitation Pacific Sanitation Challenges Wastewater Sources and Constituents Environmental and Public Health Impacts Key Factors in Managing Wastewater Options and Constraints New Zealand Case Study Take Home Messages

3 To discharge wastewater back into the environment so as to protect public health and to ensure environmental assimilation Assimilation - wastewater is absorbed into the environment sustainably Wastewater means contaminated water from toilets and washing facilities - village houses, institutions, schools and hospitals, industrial and commercial operations e.g. fish factories

4 Changing expectations increasing water consumption and wastewater generation Increasing pressure from industry and tourism on limited water resources Traditional sanitation systems ill equipped High tech treatment systems prone to breakdown and failure Declining quality of shallow groundwater in unsewered urban areas Rising sea-water levels reduce in-soil treatment effectiveness More frequent cyclones leading to more frequent flooding overwhelming wastewater systems / public health risks Facilities to handle sludge

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6 Solid waste 2-3% of domestic wastewater Fats, oils and greases and debris Hydrogen sulphide, ammonia, methane, carbon dioxide, sulphur dioxide and nitrogen oxides; also VOCs

7 Inorganic chemicals: dissolved salts e.g. nutrients (N, P), trace metals Organic chemicals: dissolved carbonaceous material, oil & grease, synthetic organic compounds Emerging contaminants: antibiotics, drugs, industrial & household products, sex & steroid hormones, nano-materials, micro-organisms Microbiological constituents: bacteria, viruses, parasites and others Physical characteristics: temperature, colour, solids, turbidity, odour, conductivity

8 Constituent Carbon organic material Nutrients Pathogens (bacteria, protozoa, viruses, etc) Solids (floatable and settleable) Dissolved salts Effect Deplete oxygen in water; Anoxic or anaerobic conditions and death of plants and organisms, foul odour Ammonia - toxic to fish, nitrogen & phosphorus promote aquatic plant growth, eutrophication Cause infection and illness in humans; can bioaccumulate in shell fish Floating solids block out sunlight, inhibit oxygen transfer, kill plants and organisms. Settleable solids cover beds killing benthic organisms Change conductivity and salinity affecting sensitive organisms. Sodium can alter soil permeability

9 Constituent Metals Organic carbon compounds resistant to break down Effect Toxic in high concentrations. Can accumulate in sediment and bio-accumulate in organisms Smother biological growth Deplete dissolved oxygen by covering growth May degrade but not biologically Emerging contaminants Oil & grease Contain toxic chemicals Chemicals (e.g. Endocrine disrupters, hormones, pesticides), micro-organisms, nano-materials Inhibit oxygen transfer, aggravate anoxic/ anaerobic conditions, smother biota

10 Constituent Metals Refractory organic carbon compounds Emerging contaminants Oil & grease Effect In high concentrations, these can be toxic. If in a particular form, they can accumulate in a stream bed or bio-accumulate in organisms Smother biological growth Contribute to depletion of dissolved oxygen in water with associated effects, particularly if deposited in a thick layer (may not be biodegradable according to BOD test but still degradable) Contain toxic chemicals Chemicals (e.g. Endocrine disrupters, PPCPs), micro-organisms, nano-materials, Inhibit oxygen transfer, aggravate anoxic/ anaerobic conditions, smother biota

11 Nutrients causing excess weed growth Laundry discharge and Litter

12 Typhoid bacteria - Wastewater pollution Giardia Parasite Cryptosporidium Cysts

13 Community Knowledge & Understanding Institution al knowledge and systems Physical Environment Costs and Funding Impacts and Effects 1. Cultural and Social Pathways 2. Understanding public health 3. Contamination Risks 1. Regulations and guidelines 2. Available systems 3. Quality assurances system and monitoring 1. Urban versus rural 2. Topography 3. Soils 4. Climate 1. Capital and life cycle costs 2. Complexity 3. Local vs imported 4. Owner / technician 1. Groundwater quality effects 2. Drinking water effects 3. Sensitive ecosystems 4. Lagoon water quality

14 Rural Urban Low population density Lower water use / fewer appliances Much open space with foliage Few commercial and industrial processes Higher population density Higher water use / more water using appliances Little or no open space; little foliage Many processes e.g. hospitals, garages, warehouses.

15 Physical Feature Advantage Disadvantage Flat Topography Ease of construction Poor stormwater runoff Water-logging Steep topography Positive drainage Land instability Construction difficulty Poorly Draining High stormwater runoff High groundwater Slow Draining Soils Rapid Draining Soils Effective in-ground treatment Rapid infiltration Small footprint Low application rate Large land area Limited treatment Contamination Risk High Saturated soils Flooding / overloading

16 Option Description Constraints Waterless Systems Pit privies Septic tank based systems Package plant systems Custom designed systems Hole in soil with structure over holes. Septic tank and soil soakage field Off-the-shelf type systems many types and suppliers Proven technologies e.g. trickle systems, SBRs, oxidation ditch Privy needs relocating periodically unless pumped. Good ventilation system important Large area for soakage system High cost Area for soakage system Maintenance Spare parts supply Need for appropriate technology Cost

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19 Primary Settlement Tank Secondary Settlement Tank Aeration tanks Aeration

20 Trickling Filter Sequence Batch Reactor Clarifier Oxidation Ditch

21 What is required? Understand your soil Where is the water table or limiting horizon? How much wastewater and when? Determine sustainable soil application rate Select treatment suited to land disposal Monitor and maintain The detail? Texture; pans; permeability; depth Depth; permanent or perched; changes during the year; water-logging Flows and loads; daily, weekly and annual variation Infiltration; evapotranspiration; seasonal changes Determine treatment quality required; identify any drainage control required Check groundwater levels; carry out necessary maintenance

22 New Zealand Case study: Local authority seeking to address on site system problems Focus is on land application of treated wastewater Key Local Issues Flat topography, poor drainage and high rainfall Knowledge-based approach involved: 1. Guide to local soil types and suitability to land application 2. On-site system design guide based on AS/NZS Proforma for Assessing Building and Consent applications 4. Workshops for regulatory staff and local practitioners

23 Silt loam with clay rich top-soil Short term waterlogging Compact slowly permeable sub-soil Extensive ponding / absence of stormwater infrastructure

24 Soil Moisture Graph for Invercargill Approaches Provide drainage to remove perch groundwater and maintain unsaturated soil depth Manage surface stormwater runoff provide diversion and drainage Special designs mound systems or subsoil drainage

25 Soil maps based on Topo climate soil data Soil descriptions applicable for land application Soil categorisation to AS/NZS 1547: 2000 Soil Characterisation and Investigation Methodology Soil unit risk profiles Soil investigation guidelines Qualified Investigator

26 Local design guide addressing: o site investigation procedure o design and construction methods o operation, maintenance and monitoring procedures Specific reference to AS/NZS 1547: 2000

27 o Standardised against Building Act (Method G13/VM4 Foul Water) o Referenced to On-site Standard (Part 4, AS/NZS 1547) o Readily communicable format o Efficient and transparent o Reviewed by competent person

28 Workshop collaboration of all parties Staff/regulators, public health officers, practitioners Develop common understanding Build consensus for holistic solution Workshop 2008 Information and Training Informing staff and practitioners Training in use of Tools Seeking feedback and improvement Workshop 2010 On-going training of staff and practitioners Raise awareness of new issues

29 Good deep groundwater separation but Shallow perched water table impacting on wastewater suitability

30 Soil and Site Assessment 1. Soil assessment needs practice 2. Soils info needs to be interpreted 3. Drainage and runoff critical 4. Seasonal changes in water logging critical 5. Skilled and trained assessors 6. On-going monitoring to improve and refine assessment procedures 7. More robust approach for large systems and cumulative effects is needed Design and Specification 1. Needs to address soil drainage, and surface water management 2. Adequate drawings for construction of treatment and land disposal systems 3. Include manufacturer s instructions 4. Clear testing and commissioning procedures 5. Means of checking compliance with standards 6. Skilled and trained designers, installers and maintenance operators

31 1. Critical issues - drainage and water-logging 2. Knowledge-based approach has improved consent applications 3. Learning about environment and constraints led to improved design 4. On-Going pressure for development in areas unsuited to on-site wastewater 5. Further work Monitoring regimes to better understand design and system performance. Storm water infrastructure to support on-site wastewater systems Groundwater mounding and of designs that accommodate mounding.

32 Recognising need for change- community awareness Strategic plan knowledge-based approach culturally, socially, technically; appropriate technology, affordable Planning systems - rules, standards, cost estimation and funding Building systems regulatory, institutional, practitioners Operate and maintain systems quality assurance Monitor systems and environment

33 PROBLEM Deteriorating sanitation conditions environmental effects, public health impacts SOLUTIONS A strategic, localised, knowledge based approach can: Improve understanding of the physical environment Improve design and treatment outcomes Identify critical constraints requiring non-traditional approaches Total systems approach investigation, planning, assessment, design, regulation and monitoring required for sustainable outcomes New Zealand experience with different physical environments provides lessons for south Pacific countries in on-site wastewater management