Effluent Treatment Options Research Articles

A nature-based solutions approach to managing shrimp aquaculture effluent

While coastal habitat conversion was a primary environmental concern in Asia for the mostly extensive shrimp aquaculture sector in previous decades, the transition towards intensive production is creating new environmental risks, primarily water quality impacts from nutrient-rich effluent. There is a need to compare the performance of conventional and Nature-based Solution (NbS) effluent treatment options given the increasing nutrient loads from more intensive aquaculture and historic loss of ecosystem services from mangrove deforestation. This study evaluates the potential for common and emerging effluent treatment systems to address total nitrogen and total phosphorus effluent from shrimp farms across a spectrum of production intensities. Nutrient waste loading for four stocking density scenarios (7PLm-2, 20PLm-2, 75PLm-2, and 120PLm-2) are estimated to compare the treatment efficiency, economic feasibility, spatial requirements, and ecosystem service provision of conventional and NbS effluent treatment systems. We use secondary data to assess effluent treatment systems applicable for shrimp aquaculture in Asia. Findings provide the conceptual framework for comparing the characteristics and tradeoffs of aquaculture effluent treatment systems. Constructed mangrove wetlands are an NbS approach that can meet the intensification needs of aquaculture producers and reduce negative impacts from aquaculture effluent at competitive costs, while also providing ecosystem service co-benefits.

Evaluation of treatment options for Atlantic Canadian seafood processing plant effluent

The purpose of this study was to evaluate different effluent treatment options for Atlantic Canadian seafood processing plants. Bench-scale testing with a 25-mesh screen, sedimentation (SED), and dissolved air flotation (DAF) was conducted. Treatment by SED and DAF was successful in reducing contaminant concentrations with maximum observed percent reductions: biochemical oxygen demand, BOD5 (90%); chemical oxygen demand, COD (60%); turbidity (99%); total suspended solids, TSS (95%); and ammonia nitrogen, NH3-N (50%). Bench-scale 25-mesh screen runs for select effluent types showed poor reduction efficiencies and appeared to provide inadequate removal of contaminants. Sedimentation and DAF using alum were effective at removing solids but less effective at removing soluble effluent components. Improved performance may be possible with further treatment technology optimization on an effluent specific basis.

ECONOMIC ANALYSIS OF ALTERNATIVE EFFLUENT TREATMENT OPTIONS FOR POND PRODUCTION OF HYBRID STRIPED BASS IN AURORA, NORTH CAROLINA

The focus of this article is the post-harvest treatment of effluent from hybrid striped bass (HSB) pond aquaculture to meet effluent discharge standards for Biochemical Oxygen Demand (BOD; 5 mg/L) and chlorophyll-α (40 μg/L) established by the North Carolina Division of Water Quality (DWQ). The specific application is to HSB pond aquaculture in Aurora, North Carolina. A variety of effluent treatment options were proposed and evaluated based on their efficacy in reaching the new standards on a 28.8-ha (72-acre) HSB farm. The economic feasibility of the proposed options ranged from positive $499 to negative $121,691 using the partial budget methodology. Our results indicate that retaining water on-farm for subsequent production cycles instead of discharging had the highest positive impact ($499) on annual farm budgets and may reduce production costs without compromising fish yields. Application of effluents onto existing or newly planted trees was also an attractive alternative because of the possible generation of additional income and the conversion of a point source discharge into a non-point discharge. By conversion of a point source into a non-point source the pond effluents would also benefit from the additional biological treatment and filtration of the effluents by the trees and the associated soil organisms.

Evaluation of treatment options for Atlantic Canadian seafood processing plant effluentA paper submitted to the Journal of Environmental Engineering and Science.

The purpose of this study was to evaluate different effluent treatment options for Atlantic Canadian seafood processing plants. Bench-scale testing with a 25-mesh screen, sedimentation (SED), and dissolved air flotation (DAF) was conducted. Treatment by SED and DAF was successful in reducing contaminant concentrations with maximum observed percent reductions: biochemical oxygen demand, BOD5 (90%); chemical oxygen demand, COD (60%); turbidity (99%); total suspended solids, TSS (95%); and ammonia nitrogen, NH3-N (50%). Bench-scale 25-mesh screen runs for select effluent types showed poor reduction efficiencies and appeared to provide inadequate removal of contaminants. Sedimentation and DAF using alum were effective at removing solids but less effective at removing soluble effluent components. Improved performance may be possible with further treatment technology optimization on an effluent specific basis.

Impact of trout aquaculture on water quality and farm effluent treatment options

In the context of the European Water Framework Directive, the in- and outflow water quality from 13 German trout farms, rearing mainly rainbow trout (Oncorhynchus mykiss) and using inflow rates between 0.03- 0.80 m 3 s −1 , were monitored for point-source pollution. The farms had a significant effect on the effluent quality and macro-invertebrate fauna in adjacent streams (saprobic index based on species assemblage and abundance was 1.56- 2.10 upstream of the farms but increased to 2.06-2.37 downstream of the farms). Inflow water quality, type of rearing unit, feeding intensity (amount of feed input in relation to water resources) and effluent treatment method could be used to predict effluent quality by 50 to 88% for most water characteristics. Based on these results, different effluent treatment options were monitored for their treatment performance. Concrete sedimentation basins 11 m × 7m × 1.2 m and 5.5 m × 3.3 m × 1.5 m (L × W × H), respectively, used for total farm effluent had little or no treatment effects. The micro-screen examined was relatively effective on particulate water components, measured as total phosphorous (TP), biochemical oxygen demand (BOD5), chemical oxygen demand (COD) and total suspended solids (TSS), resulting in treatment efficiencies of 29-53%, which is less than expected from data in the literature. The constructed wetland ex- amined showed the highest treatment efficiency: more than 35% for TP, COD, BOD5, TSS and total ammonia nitrogen (TAN). From these results and data from the literature, treatment strategies for trout farm effluents can be developed, depending on the rearing system and production intensity.

Treatment options for effluents from a solid waste transport station

In this study the wastewaters originating from solid waste transport stations that are established to compress the collected solid wastes from households in order to ease further transportation to final disposal sites (e.g. sanitary landfills) were investigated in terms of characterization and treatability. The results of conventional characterization showed that although the strength of wastewater may be subject to changes depending on the amount of water used for site cleaning, the effluents can be classified as strong wastewaters. Unlike the landfill leachates the mentioned wastewaters did not contain excessive amounts of nitrogen. The soluble COD of the wastewaters accounted for approximately 80% of the total COD, emphasizing the predominance of soluble organic pollutants. To remove soluble organics on the other hand, although both chemical oxidation processes and biological treatment such as aerobic systems; anaerobic technologies or a combination of both anaerobic and aerobic processes can be applied, biotreatment overcomes chemical oxidation due to economic concerns. Assessment of inert COD fractions under aerobic and anaerobic conditions indicated that an anaerobic process must be applied as the first unit of the treatment scheme. However since it was not possible to comply the discharge limitations of 160 mg l –1 COD by solely using an anaerobic biological treatment, an additional treatment unit i.e. aerobic biological treatment or chemical oxidation etc. following the anaerobic one must be used. It was recommended to run additional experimental research to find out more about both the proper type and the optimal operating conditions of the mentioned second treatment unit.

Nutrient reduction evaluation of sewage effluent treatment options for small communities

Small communities that are sewered by either package sewage treatment plants or on-site sewerage facilities are finding that the ground and surface waters are being contaminated. Nitrogen, which typically is not removed in these conventional systems, is a major concern. This project evaluated the capability of four sewage treatment technologies to reduce the amount of nitrogen being discharged in the effluent to the receiving environment. The four sewage treatment processes evaluated include a recirculating sand filter, biofilter, slow sand filter and constructed subsurface flow wetland. These processes were evaluated for their capability to reduce nitrogen, phosphorus, BOD5 and TSS. The primary objective of the project was to evaluate the capability of these treatment processes to reduce nitrogen using biological processes nitrification and denitrification. This paper reports on the performance of these processes to reduce nitrogen. The study demonstrated that the biofilter was capable of removing from a primary treated influent 40% of the total nitrogen. For the same quality influent the recirculating sand filter was capable of removing 35% of the total nitrogen. Secondary treated effluent was fed to the slow sand filter and the subsurface flow wetland. There was a 52% reduction in total nitrogen through the wetland however there was virtually no reduction in total nitrogen through the slow sand filter.

The economic impact of proposed effluent treatment options for production of trout Oncorhynchus mykiss in flow-through systems

The United States Environmental Protection Agency has considered several treatment options for flow-through systems in its Effluent Limitation Guidelines rulemaking effort on aquaculture. However, the economic effects of treating effluents can impose high costs on aquaculture businesses, depending upon the treatment option selected. Survey data from trout farmers in North Carolina and Idaho were used to develop enterprise budgets, a spreadsheet-based risk analysis, and mathematical programming models of medium-sized trout farms in North Carolina (68,182 kg/yr) and Idaho (90,909 kg/yr) and large trout farms in Idaho (1,136,364 kg/yr). These analyses were used to examine the effect of imposing five different effluent treatment options on the net returns of farms raising trout in raceways. Budget analyses showed that the trout farm scenarios considered were generally profitable, although the medium-sized farms exhibited low levels of profitability. All five proposed effluent treatment options resulted in negative net returns for the medium-sized farms in both North Carolina and Idaho. The large farm scenario showed positive net returns after adding costs associated with the affluent treatment options considered, but the risk of generating positive net returns decreased from 82–84% to 10–11%. Thus, financial risk increased considerably when treatment options were imposed. The mixed-integer mathematical programming model demonstrated sensitivities to the level of credit reserves both for operating and investment capital. The effluent treatment options imposed on the models were not economically feasible at the levels of capital available on most trout farms. Subsequent runs of the model used investment capital requirements of treatment options at 50% of the original estimates. The models showed that imposing effluent treatment options forced farms to substitute production units for treatment facilities. This results from a combination of: 1) the additional capital requirements of the treatment options; 2) limited availability of credit reserves; and 3) competing uses for land in trout farming areas that put upward pressure on land prices. Many of the proposed treatment options included substantial investment capital requirements that increased annual fixed costs. Limited availability of investment capital prevented the farm expansion that would be needed to spread the increased fixed costs; hence, the models were forced to remove units from production to meet treatment constraints. Net returns decreased because farms were forced to operate at inefficient levels.

Treatment of shrimp farm effluent with omnivorous finfish and artificial substrates

Long-term environmental sustainability and community acceptance of the shrimp farming industry in Australia requires on-going development of efficient cost-effective effluent treatment options. In this study, we aimed to evaluate the effectiveness of a shrimp farm treatment system containing finfish and vertical artificial substrates (VAS). This was achieved by (1) quantifying the individual and collective effects of grey mullet (Mugil cephalus L.) and VASs on water and sediment quality, and (2) comparing the retention of N in treatment systems with and without the presence of finfish (M. cephalus and the siganid Siganus nebulosus (Quoy & Gaimard)), where light was selectively removed. Artificial substrates were found to significantly improve the settlement of particulate material, regardless of the presence of finfish. Mullet actively resuspended settled solids and reduced the production of nitrate when artificial substrates were absent. However, appreciable nitrification was observed when mullet were present together with artificial substrates. The total quantity of N retained by the mullet was found to be 1.8– 2.4% of the incoming pond effluent N. It was estimated that only 21% of the pond effluent N was available for mullet consumption. When S. nebulosus was added, total finfish N retention increased from 1.8% to 3.9%, N retention by mullet also improved (78±16 to 132±21-mg N day−1 before and after siganid addition respectively). Presence of filamentous macroalgae (Enteromorpha spp.) was found to improve the removal of N from pond effluent relative to treatments where light was excluded. Denitrification was also a significant sink for N (up to 24% N removed). Despite the absence of algal productivity and greater availability of nitrate, denitrification was not higher in treatments where light was excluded. Mullet were found to have no effect on the rates of denitrification but significantly reduced macroalgal growth on the surface of the water. When mullet were absent, excessive macroalgal growth led to reduced dissolved oxygen concentrations and nitrification. This study concludes that the culture of mullet alone in shrimp farm effluent treatment systems does not result in significant retention of N but can contribute to the control of macroalgal biomass. To improve N retention and removal, further work should focus on polyculturing a range of species and also on improving denitrification.

A Mixed Integer Programming Analysis of Effluent Treatment Options Proposed for Pond Production of Hybrid Striped Bass, Morone chrysops X M. saxatilis

The growth of aquaculture farming has resulted in increased scrutiny by regulatory agencies. The Environmental Protection Agency (EPA) added aquaculture into the Effluent Limitation Guidelines (ELG) program that bases its rulemaking effort on technology-based standards that are economically achievable. The primary objective of this paper is to evaluate several effluent treatments that have been considered for hybrid striped bass (HSB), Morone chrysops X M. saxatilis, farming in pond production systems. A mixed integer programming (MIP) analytical model for HSB farming was developed focusing on maximizing profit derived from HSB production subject to the imposition of several different effluent treatment options. Settling basins and constructed wetlands entail high costs for farmers with high reduction in effluents. Filtering treatments incur high cost without much reduction in nutrient concentration in effluents. Not flushing water from the pond, or not draining the pond annually, reduces effluent volume. Reduction in the amount of water flushed or drained from the pond also decreases operating costs without any additional investment cost associated with adoption of the treatments. It is estimated that various effluent treatment options would increase production costs on average by $0.001-6.79 per kg. The main result of the MIP model is that no annual draining and not flushing the pond water are the best operational treatments. When effluent level standard regulations are imposed on effluent discharge, the model selected the no draining treatment. By not draining ponds, farms would minimize treatment cost by reducing effluent volume. Additional work is needed on the long-term risks associated with not flushing or not draining HSB production ponds.