Biohavens – the only truly bio-mimicking floating wetland – Case Study #20 – nutrient removal

14 November 2015

Nutrient Removal from Reclaimed Water with Floating Treatment Wetlands

Project Location: Pasco County, Florida USA

An independent study conducted by CH2M Hill demonstrates the ability of BioHaven® floating treatment wetland (FTW) technology to further reduce nutrient levels in reclaimed municipal wastewater, which would assist in meeting total maximum daily load (TMDL) limits. In addition to removing total nitrogen (TN) and total phosphorus (TP), FTWs provided the ancillary benefits of:

  •   Increasing wildlife habitat;
  •   Reducing local nuisance insect populations; and
  •   Increasing pond aesthetics.

Overview

CH2M Hill supervised installation of 20 FTWs in a test pond containing approximately five million gallons of reclaimed water from the Pasco County Master Reuse System (PCMRS). Each FTW measured 8 ft x 10 ft and accommodated 154 plants. The primary objective of this study was to quantify nitrogen removal by the FTWs, in the hopes of demonstrating the benefits of FTWs in TMDL-limited watersheds. Total nitrogen is the parameter currently limiting reclaimed water use within the PCRMS. FTWs were envisioned as a more efficient alternate to treatment wetlands where land area may be constrained.

Screen Shot 2015-11-11 at 14.39.23

The PCMRS is a regional reclaimed water transmission and distribution system providing wastewater effluent disposal for Pasco County and the City of New Port Richey. With 15 golf courses and approximately 12,000 residential users connected, the PCMRS reclaims approximately 20 million gallons per day (mgd) of advanced secondary treated effluent from seven local WWTFs.

Water Quality Effects

FTWs had a positive effect on TN, TP and pH as shown below:

Screen Shot 2015-11-11 at 14.39.31

Removal of TN and TP was substantially higher during the FTW performance period than during the control period. Nutrients were still removed during the control period, probably due to some bacterial activity and solids settling in the test pond. However, bacterial and plant nutrient removal processes were substantially enhanced during the performance period. Net nutrient removal rates attributable to the FTWs can be calculated by subtracting the control removal from the performance removal. Those rates, based on the amount of FTW present in ft3, were 1.7 lb/yr/ft3 for TN and 0.54 lb/yr/ft3 for TP.

Most of the total nitrogen was present as nitrate. It was found that water temperature, which averaged 23oC during the performance period, did not affect nitrate removal over the temperature range examined.

pH increased in the test pond as algal photosynthesis produced a large amount of alkalinity. However, this pH increase was mitigated during the performance period and values (recorded automatically every hour) were much less variable with the FTWs.

No removal of TSS or BOD was seen in the study. TSS increased by over an order of magnitude due to algal growth in both the performance and control periods. The influent BOD was typically less than 5 mg/L.

Removal Mechanisms

It has been noted in previous FTW studies that only 10-20% of the nutrient removal is performed by plants, with the majority of nutrient removal performed by bacteria attached to the FTW matrix and plant roots (biofilm). In the Pasco County study, plant samples were harvested during the performance and control periods to analyze the nitrogen, phosphorus and carbon contained in the plants. It was estimated that only 0.3% of the nitrogen removed was contained in above-ground plant matter during the performance period, and 0.8% during the control period. The remaining nitrogen removal can be attributed to plant roots, bacterial activity and chemical/physical processes. A mass balance estimated that 57% of the TN removed during the performance period was denitrified to nitrogen gas.

Ancillary Benefits

Four main benefits have been historically attributed to FTWs:

  1. Water purification,
  2. Habitat improvement,
  3. Erosion protection and
  4. Enhanced landscapes.

Benefits identified in the Pasco County study were:

  •   Wildlife habitat. Wildlife was observed on several occasions utilizing the FTW habitat. Birds included black-necked stilts, clapper rails, boat-tailed grackles and ducks (which built nests). Turtles were also observed resting on the FTWs.
  •   Nuisance insect species control. The FTW habitat also benefits smaller organisms such as aquatic and terrestrial insects. These invertebrates find refuge and food sources within the dense submerged roots and emergent vegetation. Insects that are dependent on water bodies for habitat, such as dragonflies and damselflies, can help reduce the local populations of nuisance species through natural predation. During the performance period, WWTF staff noted no large hatches of midges, which can be a nuisance to people and even be vectors for the spread of diseases such as West Nile virus, and – contrary to previous years – there were no complaints by neighboring residents.
  •   Aesthetics. Adding FTWs to the WWTF pond increased the overall aesthetics. The variety of grasses, rushes and flower plants on the FTWs provided natural aesthetics to a pond otherwise devoid of vegetation.

Conclusions

  •   Floating treatment wetlands (FTWs) installed in a test pond removed substantial concentrations of total nitrogen and total phosphorus from reclaimed water. Nutrient removal with FTWs was significantly greater than when the FTWs were removed from the system.
  •   Plant uptake provided only a small percentage of the total nitrogen removal.
  •   FTWs provide productive habitant for invertebrates and wildlife. A diverseselection of vegetation and species was sustained on the islands.

{This is the last of 2o case studies published in this series}

Lots of apparent irregularities around the Elandsfontein phosphate mine?

13 October 2015

Elandsfontein looking west towards the lagoon (Carika van Zyl)

Elandsfontein, looking west towards the lagoon (Carika van Zyl)

The goings-on around the approval of mining rights for the proposed phosphate mine on the South African west coast at Elandsfontein (in the buffer zone of the West Coast National Park no less!), seem a tad murky.  There seem to be a slew of procedural anomalies and some of the specialist work, for a project that could, potentially, have ecological implications that extend into the marine environment, appears somewhat superficial – with concerns raised on review.  Political interference in favour of the mining has been alleged.  Legal opinion shows that the mining company may have been ill-advised in terms of their procedural obligations to seek approval under NEMA.  Anyway, readers need to draw their own conclusions from the following letter prepared by the stalwart conservationist heading up the opposition to the mine, Carika van Zyl.  Last week she circulated this letter with associated documents (published here with her permission):

Read more »

Water quality is a problem in South Africa: has the penny finally dropped… ?

30 July 2015

Wastewater effluents destroy rivers and lakes (Photo: Bill Harding)

Wastewater (sewage) effluents are the major threat to South African reservoirs (Photo: Bill Harding)

A pleasing development this week has been the long-overdue acknowledgement that water quality is the ‘elephant in the room’, insofar as the optimal future use of South African water resources is concerned (see article here).  Of course this is not a new discovery – the lack of attention to water quality issues has been bemoaned for a very long time (a simple search of this blog will reveal many related articles and cautions over the past five years) – yet the warnings have been ignored or now seemingly considered to have been part of a ‘debate’.  On the debate issue, however, no formal collegiate interactions have been initiated, other than a very short-lived one-day attempt by the Water Research Commission a couple of years ago.  Some who may consider the ‘debate’ to now be over, have themselves been instrumental in denying the existence of a water quality problem for a long time.

So, if the attitude is now changing, this is very good news – especially that the responsible national department is now apparently moving towards developing an Integrated Water Quality Management initiative – lets hope they don’t waste any more time reinventing wheels.  While fingers are being pointed at a ‘piecemeal’ approach to the problem by the Dept of Water and Sanitation, one can only ask why their consultant advisors did not alert them to the dangers of ignoring water quality issues for so long?

FACT: With inadequate quantities of freshwater, development in South Africa will be severely constrained. If the quality of these limited supplies is also compromised, prospects for sustainable development effectively disappear.  These simple truths have been clear and evident in South Africa for several decades.

Read more »

Can an ecosystem service approach strengthen river conservation?

2 May 2014

River Ribble, Lancashire. Image RSJ

River Ribble, Lancashire. Image RSJ

Worldwide efforts to conserve river ecosystems are failing, and new approaches for stronger conservation planning are required.  This is the underlying context of a new editorial ‘Rebalancing the philosophy of river conservation’ by Mars [Managing Aquatic Ecosystems and Water Resources under Multiple Stress] scientist Steve Ormerod in Aquatic Conservation Marine and Freshwater Ecosystems.  Ormerod suggests that the ecosystem service approach can offer a valuable addition to current river conservation strategies, potentially providing convincing new arguments to help halt freshwater biodiversity loss. Read more »

John Russell Harding

1 May 2014

John Russell Harding 15.2.1917 - 30.4.2014

John Russell Harding 15.2.1917 – 30.4.2014

Ghana’s true State of the Nation address (SONA)

28 February 2013

South Africans recently listened to yet another ho-hum State of (our) Nation Address (SONA) – an utterly boring and inept re-run of vague promises and intentions, all of which have been heard before, remain in limbo and did nothing to invigorate the nation.  Opposition party criticism devolved to the usual critiques, lacking in any rigorous substance but providing an opportunity to do some flag-waving.  The fact that so many of the opposition party members saw fit to dress up in fantasy ball outfits to attend the annual parliamentary opening made me shudder.

Ghana is often mentioned as the most dynamic country in Africa, rapidly eclipsing South Africa’s long-unchallened but now rapidly decaying claim to this title.  At least they have an opposition party that has the chutzpah to come out with a detailed and unemotional response to their SONA, in the form of the Ghanaian NPP’s True State of the Nation (TSONA) (see full statement). Read more »

Mining of oil sands contaminates water sources

11 January 2013

Quite a few years ago I attended an ASLO meeting in Alberta, Canada, at a time when the next big thing in oil production was the extraction of oil from tar sands in the Athabasca region.  The debate was a lot similar to that around the issue of fracking, denial on one side and lots of concern and worry about environmental impacts on the other.  However, like the current E-tolling saga in South Africa – the debate will eventually die off and the mining or tolling will simply go ahead – i.e. Big Capital wears down the opposition over time and get their way in the end. Read more »

New Jersey River = “vilest swillhole in Christendom”

14 October 2012

I think you will agree that this is not the description that you would want for a river that you live near or, if your heart is in the right place, for any river at all.  Yet, this is how the poet William C Williams described New Jersey’s Passaic River back in 1956. Read more »

US and Canada sign pact to fight eutrophication and lake pollution in the Great Lakes

9 September 2012

Not many will remember the bizarre event back in 1960 when the Cuyahoga River – which flows into Lake Erie, became so polluted that it actually caught fire.  This event catalysed a whole raft of efforts to improve the lake’s water quality – which were highly successful but not sustained, such that Erie is these days appearing again in reports about pollution.  The most recent outcome has been the signing of  a pact between Canada and the USA to work towards improving the conditions in the Great Lakes. Read more »

African environmental journalists urged to up their game

5 September 2012

Lake Victoria, source of food, water and income to millions of central and east African inhabitants, is in dire straits.  Pollution levels are increasing and the scourge of water hyacinth has again reached astronomical levels – following its near eradication a decade ago.  Journalists from the region, better than most at appreciating environmental issues, have been challenged to do more.  The challenges are considerable and there is a need to sustain efforts, not tackle the problems piecemeal. Sound familiar? Read more »