Origins of On-site Wastewater Design Loading Rates

The “Nz-onsite-wastewater” forum (http://nz-onsite-wastewater.freeforums.net/) created in August 2018 includes a discussion thread relating to the variation in design loading rates (DLR) for land application of treated effluent where a new forum member raises questions re differences in DLR/DIR values in TP58, AS/NZS 1547 and those in the proposed new GD006. The Forum Administrator, Grant Hammond of Tauranga, makes the following comments on this matter:

It would be nice to think that our national design standards were all based on first principles of engineering design, but unfortunately all too often they include design parameters and fudge factors that have never been proved and are often derived from an assumption that was based on a prior assumption! TP58/GD06 and NZS 1547 are all primarily based on desktop compilations of other design standards and research.

I suspect TP58 had a stronger US influence, whereas NZS 1547 obviously had a strong influenced from Aussie. I can only assume these influences contributed to the different correlations between DIR and soil categories.

Perhaps someone who was involved in the NZS 1547 standard and knows a bit of the history behind the drafting of NZS 1547 could chip in on this question

As the author of TP58 Editions 1 and 2 (1989 and 1994) and as a participant in the Joint Standards committees that produced the 2000 and 2012 versions of AS/NZS 1547, On-Site NewZ has some insight into the process of drawing up design parameters. A discussion on this topic entitled “Design Loading Rates – Origins and Development in On-site Wastewater Manuals and Standards” can be accessed from the Pages Sidebar of this Blog.

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Auckland Council Guideline Document: On-site Wastewater Management in the Auckland Region [GD06-2018] – Updated Draft, September 2018

Dr Gretel Silyn Roberts, Principal – Technical Guidance, Engineering and Technical Services, Infrastructure & Environmental Services at Auckland Council, has advised On-Site NewZ of the issue of an updated draft of GD06 as follows.

Update:
Thank you to all those who have provided initial feedback on GD06 – On-site Wastewater Management in the Auckland Region. We very much appreciate the effort put into the review of this draft. The deadline for feedback is October 12th, but we would much appreciate you sending through any major issues or questions prior to this date so we can address them fully.

Update of amended draft:
Based on feedback to-date, and some suggested changes, we have updated the document on the Auckland Design Manual website. Most changes are adjustments to cross references, corrections and clarifications.

The key changes we would like you to be aware of are:

1. Section D: Wastewater treatment units –

(a) Adjustment to the text around Section D1.4.3 Septic tank sizing

(b) Restructuring of Section D1.5.5 – Types of system

  • Removal of trickling filter
  • Removal of single pass packed bed filter
  • Removal of multi pass packed bed filter
  • Removal of diagrams for all “Alternative treatment systems”
  • Removal of diagrams for all “Alternative toilet systems”

2. Section G: Risk – Additional comment around the need to design for climate change

Please do not hesitate to contact our team if you have feedback.

Gretel Roberts Gretel.Roberts@aucklandcouncil.govt.nz

To access a PDF version of the September 2018 update go to the Pages sidebar and the topic heading for this Blog Item.

NZ ON-SITE WASTEWATER FORUM START-UP, August 2018

Following the July 2018 release of the draft of GD06, the Auckland Council “Guideline Document: On-site Wastewater Management in the Auckland Region”, Grant Hammond of Tauranga has set up a ProBoards forum entitled “Nz-onsite-wastewater” at http://nz-onsite-wastewater.freeforums.net/.

Grant is a Bay of Plenty Regional Council approved on-site wastewater designer and a principal of Technologyworks Consultancy. In his introduction to the forum Grant says:

“We now have national standards AS/NZS 1546:2008 and 1547:2012 for treatment systems and land application systems and a national testing program for aerated wastewater treatment systems, plus numerous design manuals and guidelines produced by Territorial Authorities and Regional Councils….yet I seem to now have more questions than ever!

OSET designers come from a range of disciplines with varied practical and theoretical training and experience. Some come from a hands-on background (drainlayers), some from an engineering design background like myself, and others from the building and manufacturing industries.

We all have strengths and weaknesses and hopefully this forum will provide a technical resource where we can share our knowledge, and collectively answer some of these questions.”

The forum discussion topics to date are:
• General Discussion (are media and family rooms counted as bedrooms; uncontrolled trickle loading).
• GD06 July 2018 Draft for Consultation (the cost of design; Appendix M1.0 LPED design examples).

Membership of the forum is free and it is easy to register and set up your forum name and login password.

 

 

Auckland Council Guideline Document: On-site Wastewater Management in the Auckland Region [GD06-2018] – Community of Practice Presentation, August 2018

The Auckland Council Engineering and Technical Services team which managed the development of the new on-site wastewater guideline to replace TP58 held a “community of practice” meeting in Auckland on Friday 17 August to discuss the July 2018 draft of the document. A wide invitation was extended to representatives of the on-site wastewater industry in Auckland to participate in a discussion on the development of the document, significant differences between TP58 (2004) and GD06 (2018), and the next steps in consultation toward production of the final document and its placement within the Auckland Unitary Plan.

The PowerPoint presentation delivered at the meeting prior to open discussion is available from the Pages side-bar of this Blog under the topic of this Blog item. The presentation topics covered an overview of the document structure, key changes from TP58 (2004), content of the main sections of the guideline and the next steps in consultation toward publication. Feedback sessions on technical detail. operation and maintenance, consents and Unitary Plan changes were held following the presentation.

Key issues identified for community feedback were:
• slopes (including maximums for various land application systems);
• setback distances from land application areas to site features; and
• design loading rates.

Although the official consultation period continues through to 12 October the team managing this project would very much like major feedback to be sent through over the next 3 to 4 weeks (by mid-September please).

Take a look at the presentation material from the Pages side-bar along with the July Draft of GD06 (also accessed from the Pages side-bar) and get your comments away to the Council using the instructions from PowerPoint Slide No.5 to access the feedback form.

Auckland Council On-site Wastewater Systems: Design and Management [TP58-2004] replaced by Guideline Document: On-site Wastewater Management in the Auckland Region [GD06-2018]

Auckland Council (AC) released GD06 as a draft for public consultation on 23 July 2018. The GD06 document comprises 396 pages setting out technical guidance “for the design, installation and management of on-site wastewater systems in accordance with site and soil conditions encountered in Auckland”.

Production of the new guideline was overseen by an eight person Technical Editorial Panel, with a preliminary review of the draft document carried out by Water NZ and feedback obtained from Water NZ, the NZ Land Treatment Collective, ecoEng Limited, Bay of Plenty Regional Council and Auckland District Health Board.

AC has extended thanks to 12 industry professionals (amongst others) who contributed to the document, and extended special thanks to a large number of mana whenua representatives who contributed to the work.

Access to the web version of the draft can be made through the Auckland Design Manual link:

http://www.aucklanddesignmanual.co.nz/project-type/infrastructure/technical-guidance.

A full PDF version can be accessed via the pages sidebar of this Blog at “Auckland Council On-site Wastewater Design Manual TP58-2004 replaced by Guideline Document GD06-2018”. This sidebar page includes a summary of the GD06 content and a brief comparison of the significant differences between GD06 and TP58.

AC expects the consultation period on the draft to extend from now through to October, and advises that “there will be multiple opportunities for all stakeholders to provide feedback and suggested edits:

  • a Community of Practice with industry representatives in August
  • through the Auckland Design Manual website feedback form
  • through the specific email address: onsiteww@aucklandcouncil.govt.nz“

Feedback on the content of the new guideline document will be welcomed by Auckland Council. The feedback form is accessed via the Auckland Design Manual link above.

On-site Wastewater Management at the Tuhoe Living Building

The traditional lands of Ngati Tuhoe (referred to simply as Tuhoe) are located in Te Urewera National Park and Lake Waikaremoana in the north eastern area of the North Island.

Since early settler days Tuhoe had been in dispute with the government regarding land use and neglect of community services and subsequently in 2002 brought a claim against the crown under the Waitangi Tribunal. The settlement reached in 2013 following resolution of the claim involved a substantial financial grant ($170 million), a crown apology and co-governance of their Te Urewera lands.

Tuhoe immediately began the process of establishing their tribal headquarters, Te Uru Taumatua, at Taneatua on the northern edge of the Te Urewera’s. The central feature of Te Uru Taumatua is Te Kura Whare, the tribal administrative and cultural centre. The building complex and infrastructure services have been designed, constructed, and now operated as a “living building”, certified as meeting the sustainability and zero environmental impact standards of the international Living Building Challenge.

On-Site NewZ has visited Te Uru Taumatua and the on-site wastewater system servicing the Te Kura Whare complex where a Botanical Wastewater Treatment System comprising a constructed wetland has been provided under Pure by Plants design. A review of the Living Building requirements along with information on the on-site wastewater system can be accessed from the pages sidebar of this Blog under the topic “On-site Wastewater Management at the Tuhoe Living Building”.

NZ Performance Testing – Gravelless Trench and Fabric/Textile Wrapped Distribution Pipe Treatment and Dispersal System

In February 2013 On-Site NewZ posted an item entitled “Gravelless Trenches and Fabric/Textile Wrapped Distribution Pipes”. The post introduced the topic as follows.

This technology associated with domestic wastewater septic tank effluent soakage trench systems has been around in the USA for many years, and recently entered the Australia and New Zealand market. Following an enquiry re the status of this system in the local context, On-Site NewZ has prepared a review of gravelless trench effluent dispersal systems and added it to the Pages sidebar of this blog under the title of this post.

 The issue that arose in the enquiry to On-Site NewZ was whether the wrapped pipe distribution technology was a “treatment and dispersal system” or just a “dispersal system”.

The associated review (9 February 2013) was prompted by the recent introduction into New Zealand of a proprietary system for dispersing septic tank effluent into the subsoil known as “Advanced Enviro-Septic” (AES) which originates in the USA. Basically the system comprises a patented geotextile plus plastic fibre wrapped large diameter (300mm) perforated and ridged plastic pipe laid within a “system sand” bed which disperses treated septic tank effluent into the subsoil.

The results of Canadian performance testing of the AES system carried out over 12 months in 2008 were set out in the review, and showed that the treatment accomplished through the textile wrapped distribution pipes and sand bed was better that 2.0 g/m3 cBOD and 2.0 g/m3 TSS with faecal coliforms at 218 cfu/100ml, effectively an “advanced secondary treatment” performance level.

Since 2013 Environment Technology (ET) of Nelson have designed and installed approaching 300 systems throughout NZ. In 2016 ET installed an AES system at the Rotorua On-site Effluent Treatment National Testing Programme (OSET-NTP) facility. Testing under Trial 12 ran from October 2016 to July 2017. The AES Trial 12 OSET-NTP performance certificate of 23 March 2018 shows cBOD and TSS at less than 5 g/m3 over the evaluation period, confirming that the AES system in NZ can produce advanced secondary treatment effluent quality for dispersal into the subsoil from the treatment and distribution system.

Full details of the OSET-NTP testing results along with installation details of the tested system can be accessed from: http://www.environmenttechnology.co.nz/resources/oset-testing/