Wastewater Treatment, Plant Dynamics and Management in Constructed and Natural Wetlands

Wastewater Treatment, Plant Dynamics and Management in Constructed and Natural Wetlands. Editors; (view affiliations). Jan Vymazal. Wastewater Treatment .
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The literature summarized was primarily peer reviewed published sources as well as graduate student dissertations. In some cases, however, when a source was brief e. The geographic range was the province of Ontario and eastward in Canada and the New England states. This was intended to cover a region with a similar climate and comparable agricultural activities.

Wastewater Treatment, Plant Dynamics and Management in Constructed and Natural Wetlands

Generally, indoor and laboratory experiments were not included in this review. However, in the relatively small region of northeastern North America there are no standardized design criteria. It was suggested [ 2 ] that SSF are better suited to Canadian climatic conditions because of their ability to insulate microbial communities from cold winter air temperatures, while Ducks Unlimited endorse SF systems because they are more similar to natural wetlands [ 42 ].

Therefore, it is not possible to make a conclusion based on the performance data presented in this paper. Many of the CWs considered were designed for the treatment of high solids wastewater from livestock or aquaculture operations. However, different designs can be better suited for the removal of different contaminants found in agricultural wastewater so it may be beneficial to incorporate hybrid designs to take advantage of the strengths of each design.

Many studies have compared plant species for treatment performance [ 33 , 43 , 44 , 45 , 46 ].


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Although there is no conclusive species with unanimous acceptance, Typha sp. However, it may be best to consider what wetlands plants are found within the area of construction to allow natural succession to determine the species composition after establishment. The effects of artificial aeration have been examined in a number of experiments, and it generally seems to enhance CW performance [ 26 , 44 , 48 , 49 , 50 ].

Aeration can increase dissolved oxygen DO in a CW system and stimulate organic matter decomposition and plant and microbial respiration, especially during the non-growing season when plant root zones are dormant [ 26 , 44 , 48 ]. Artificial aeration also induces mechanical mixing and engages stagnant zones to increase active wetland volume, further enhancing performance [ 49 , 51 ]. A study [ 26 ] compared two similarly loaded parallel SF CWs, one that was aerated and one was not.

However, it was concluded that the additional treatment was not significant enough to justify the cost and operation of the aeration system. Another study [ 44 ] concluded that aeration increased the removal efficiencies of TSS, TKN, and the chemical oxygen demand COD and suggest that CWs should be aerated if the costs of aeration outweigh the costs of reduced treatment efficiencies.

Colder temperatures can affect the treatment efficiencies of CWs, but certain design considerations mitigate this issue. The use of SSF versus SF helps to limit freezing because the water surface is not exposed to the atmosphere [ 2 ]. However, from the data presented in this review both SSF and SF wetlands have also been found effective during winter Table 3. Two studies [ 23 , 39 ] examined the year-round performance of SF CWs in Atlantic Canada and found that even with the seasonal fluctuations, SF CWs performed well and were suitable water treatment options.

Steps can be taken to further improve winter performance of CWs, such as allowing snow and dead vegetation to accumulate on the surface of the wetland to help insulate the system [ 2 , 49 ] and supplemental aeration can prevent freezing [ 49 ]. Two loading schedules were compared [ 25 ] to determine which would result in better overall treatment: It was found that continuous, year-round, loading was the superior option, as it performed better than the seasonally loaded system [ 25 ].

The CW consistently met effluent discharge requirements throughout the six years of monitoring [ 35 ].

The data synthesized in this review of 21 studies Table 1 , Table 2 and Table 3 also suggest that CWs are a suitable option for year-round agriculture wastewater treatment in the cold climate of northeastern North America and this will be addressed in further detail in this paper. Soil phosphorus P adsorption capacity has been identified as the limiting factor in CW treatment of agricultural wastewater, and it is suggested that research into better substrates for P removal be pursued [ 52 ]. A comprehensive assessment of a 4-cell SF system at a head dairy farm considered the P adsorption capacity of the wetland soils [ 20 , 53 , 54 ].

In eastern Canada and the northeastern USA, the most commonly researched approach to improve CW P management has been post-wetland treatment filters [ 32 , 55 , 56 ]. Many studies on this topic have taken place in northeastern North America [ 55 , 57 , 58 , 59 , 60 ]. Bench-scale experiments have involved columns filled with electric arc furnace EAF slag [ 55 ], sedimentary vs.

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The latter study retrofitted the outlet of a 28 m 2 H-SSF CW providing tertiary treatment at an aquaculture operation with pilot-scale L columns containing the best combination a first column containing medium slag, fine granite, and medium limestone, followed by a second column containing only slag [ 47 ].

From these studies, it was determined that, with appropriate substrate selection, P removal can be possible and EAF emerged as a highly effective and readily available substrate a by-product from steel manufacturers in Quebec. EAF has a P retention capacity of up to 2. These materials will inevitably reach their P retention limit and need to be exchanged, but this was taken into account by choosing readily available and affordable materials.

Despite its limitations [ 62 ], the area-based first-order model Equation 1 has become the most widely used representation of CW removal kinetics [ 63 ]: The performance of the 25 reviewed wetlands is discussed, and, when appropriate, compared to the Livestock Wastewater Treatment Database [ 1 ]. They synthesized agricultural treatment wetland performance data throughout the USA. This allows us to compare treatment performance of wetlands in the cold climate of northeastern North America with aggregated data from systems across different climates of the USA.

Along with the areal rate constants, the percentages of concentration reductions CR or log reductions LR are presented Table 1 and Table 2. A summary of the performance data separated by wetland design and season is presented in Table 3. The majority of studies found in the literature only present data in CR, so data were presented similarly here to allow for easy comparisons.

Wastewater Treatment Plant Dynamics and Management in Constructed and Natural Wetlands

CR was calculated using: The mean CRs were calculated by taking the mean of the CRs from the available data for each parameter. The standard error of the mean was also calculated by dividing the standard deviation by the square root of the sample size. Standard error is presented with the means in the text and tables. There was inter-site variation due to the different wastewater characteristics and the uniqueness of each CW.

The mean influent and effluent concentrations were higher than those reported by some [ 1 ], but the CRs were similar. The data were similar to other studies [ 1 ]. Seasonality has no clear effect on TSS removal and year round performance is satisfactory Table 3. In general, CWs are known to efficiently remove suspended solids [ 3 ], and these data reinforce that knowledge. Comparison of free water and horizontal subsurface treatment wetlands.

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