Silage effluent digestion by an upflow anaerobic filter

Silage effluent is generally regarded as one of the major agricultural pollutants of water courses. Efficient anaerobic digestion of silage effluent was achieved by a 3-day hydraulic retention in an upflow anaerobic filter. The filter was a laboratory scale unit containing a limestone chip support matrix. At loading rates ranging from 7.8 to 14.2 kg COD m⁻³ active volume day⁻¹, the average COD removal obtained ranged from 86 to 89% with a TOA removal of 82–88%. The methane content of the biogas produced ranged from 81 to 88%. The rate of COD conversion to CH₄ was independent of the loading rate under the conditions tested and the observed efficiency averaged 0.357 m¹ CH₄(STP) kg⁻¹ COD introduced to the reactor.The reactor tolerated considerable variation in influent pH without any apparent decrease in digestion efficiency. It is apparent from the results obtained that a reactor which is in routine use for slurry digestion may also be utilised for silage effluent digestion on a seasonal basis.     

Field evaluation of the treatability of type A zeolite in a trickling filter plant

Type A zeolite is a synthetic aluminosilicate which can be used as a builder in laundry detergents. The treatability of this zeolite in wastewater was evaluated in a trickling filter plant under field conditions. The normal performance of the plant was established during a baseline period of three months, after which the zeolite was added to the raw wastewater for 7 months. The removal of the zeolite by the plant averaged 81% or more at an influent concentration of 10 mg 1⁻¹. Of the zeolite that passed into the secondary effluent, 92% was removed by a dual-media filter. Removal from raw influent to tertiary effluent was thus 99%. The presence of the zeolite in the wastewater had no effect on the performance of the plant, the production of gas by the anaerobic digester or the concentrations of Pb, Zn and Ni in the effluent.     

Effluent denitrification with anaerobic filters

Experiments with two pilot-scale anaerobic filters were conducted to investigate their efficiencies in denitrifying a wastewater effluent under ambient, tropical conditions. It was found that these anaerobic filters could effectively denitrify a wide range of influent nitrate concentrations from about 20 to 410 mg l⁻¹ (corresponding to the nitrate and nitrite loadings of 50–550 g m⁻³ d⁻¹). The denitrification efficiencies achieved were between 89–98%, and a straight-line relationship between the nitrate and nitrite loadings vs the denitrification rates was observed. The specific surface areas of the filter medium employed in this study did not exhibit any significant effects upon the anaerobic filter performance. Neither filter became clogged during the 8-month operational period.     

Treatment of poultry manure wastewater using a rotating biological contactor

A pilot scale, six stage rotating biological contactor was used to evaluate the feasibility of this process for the stabilization of liquid animal manures. Total disc surface area was approx. 16.7 m². Treatment efficiencies were determined at various waste strengths and influent flow rates.With loading rates of 14.7–322 g m⁻² day⁻¹, the average COD reduction was 61%. With loading rates of 4.88-24.4 g m⁻² day⁻¹, the average BOD₅ reduction was 87%. Total nitrogen removal averaged approximately 30% for the entire study. Mixed liquor oxygen uptake rates were generally in excess of 80 mg 1⁻¹ h⁻¹.Clarified effluent was non-odorous and suitable to be reused for manure flushing or spray irrigation. Treatment was not sufficient to permit effluent discharge to surface waters.     

Thermophilic anaerobic digestion of palm oil mill effluent

A laboratory study was carried out using the thermophilic anaerobic process to treat palm oil mill effluent containing 67,000 mg 1⁻¹, COD, 31,800 mg 1⁻¹ suspended solids and a pH of 4.5. Completely mixed reactors were operated to evaluate the effects of feed strength and solids retention times on the system's performance. A range of 5–35 days solids retention time was studied. COD reduction was 72% for the 5-day unit and greater than 90% for units having detention time 15 days or more. pH of all units was self adjusted to 7.4. Gas production was, in general, greater than 0.3 m³ kg⁻¹ volatile solids feed.     

A pilot-plant scale evaluation of potential precipitants in the secondary precipitation process

Chemical precipitation of presettled domestic wastewater (secondary precipitation) was studied in three pilot-plants operating in parallel with alum, ferric iron and lime as precipitants. With all precipitants phosphates were effectively removed down to less than 0·1 mg P l⁻¹. Total phosphorus removals were closely connected to the settling properties of the flocs. The factor that seemed to influence settling properties most was pH. In a favourable pH-range it was possible to achieve total phosphorus concentrations in the effluent of less than 0·5 mg P l⁻¹. The COD removal was at an average 70, 60 and 55% with alum, ferric iron and lime as precipitants.     

Enhanced uptake of phosphorus by activated sludge-effect of substrate addition

Studies were undertaken to examine the effect of substrate addition upon the release and subsequent uptake of phosphorous by a biological wastewater treatment laboratory scale system.A train of six reactors were fed at a rate of 16 ml min⁻¹ raw wastewater using a sludge recycle ratio of 0.75 (12 ml min⁻¹). The first two reactors were simply stirred (anoxic) without the addition of air and the remaining four were aerated with excess air.Various substrates were added to the first reactor (anoxic) at different concentrations. It was determined that all the short chain substrates tested enhanced the release of phosphorus in the anoxic stages and subsequently led to increased biological uptake (removal) of phosphorus. The substrates tested included sodium acetate, acetic acid, butyric acid, ethanol and methanol.It was determined that 30 mg l⁻¹ sodium acetate was the optimum dose for biological release and uptake of phosphorus and the addition of any greater concentration had marginal effect on the ultimate removal of phosphorus.The effect of these substrates showed some specificity regarding phosphorus release, with butyric acid causing the greatest release and sodium acetate the least. However as far as phosphorus uptake (removal) was concerned, this phenomenon of substrate-specificity was less significant. For all substrates, effluent phosphorus concentration was within ± 1 mg l⁻¹ with an approximate mean concentration of 1 mg l⁻¹ residual.Phosphorus released (approx. 14 mg l⁻¹) at higher temperature (29°C) was 75% greater than at the lower temperature (24°C). Similarly the final residual phosphorus at 29°C was 33% lower than at 24°C.     

Liquid/suspended solid phase partitioning of polycyclic aromatic hydrocarbons in coal coking wastewaters

Wastewater samples were collected from five streams among two coke plants and characterized by high pressure liquid chromatography and gas chromatographic mass spectrometry. Wastewater streams included the ammonia still influent, ammonia still effluent and biological oxidation effluent. Samples collected from these streams were separated into liquid and suspended solid phases and each phase was analyzed for eleven polycyclic aromatic hydrocarbons (PAH). Total wastewater concentrations for these compounds ranged from about 2000 μg l⁻¹ in the ammonia still influent to 5–120 μg l⁻¹ in the biological oxidation effluent. Wastewater PAH were partitioned between liquid and suspended solid phases, and in most samples suspended solid phase PAH accounted for approx. 80% or more of total wastewater PAH. Partitioning in the biological oxidation effluent stream was correlated with aqueous solubility and n-octanol/water partition coefficients. Wastewater treatment consisting of sedimentation, ammonia stripping, and biological oxidation generally reduced liquid phase PAH concentrations to the range of 1 μg l⁻¹ or less. Effective removal of wastewater suspended solids will reduce total effluent PAH concentrations, hence there is need to address issues regarding removal of residual wastewater suspended material including characterization of the distribution of PAH with respect to suspended particle size.     

The treatment of leachates from domestic wastes in landfills—I: Aerobic biological treatment of a medium-strength leachate

A medium-strength leachate from domestic solid wastes in a landfill (COD 5000 mg l⁻¹, BOD 3000 mg l⁻¹ was treated using aerobic biological processes in continuous-flow, laboratory-scale reactors at low temperatures. Each unit was completely mixed, and mixed liquor was wasted such that solids retention time (SRT) was equal to the hydraulic retention period.At 10 C with addition of phosphate (COD:P less than 100:1) SRT values of 10 days were required to obtained well-clarified effluents, and high removal of BOD (>;98%) and COD (>;92%). Reduction of temperature to 5°C resulted in adverse effects on settling of sludges from units with SRT values of less than 10 days, but in other units good removal of organic materials could still be obtained. These units operated successfully with concentrations of mixed liquor volatile suspended solids (MLVSS) of 1450 mg l⁻¹, equivalent to a ratio of F/M of 0.21 kg BOD kg⁻¹ MLVSS day⁻¹ or less. Removal of ammoniacal nitrogen which took place (influent concentration 80 mg l⁻¹ as N) resulted from incorporation in biomass, and at SRT values of 10 days no nitrification took place at 5 or 10 C. Higher concentrations of ammonia in influent leachates resulted in ammonia in effluents when the ratio of BOD:N was less than about 100:3.6. Increasing the SRT of units to 20 days resulted in erratic conversion to nitrite, but reduced pH-values and possible simultaneous denitrification caused floating sludges and poorly-clarified effluents. Removal of ammonia is identified as a major problem when treating leachates, and further research is recommended.     

NTA biodegradation and removal in subsurface sandy soil

This lab-scale study examined the biodegradation and removal of nitrilotriacetic acid (NTA) in the subsurface environment, mainly sandy soils. Batch tests indicated that NTA adsorption on the sandy soils played a minor role in its removal in these soils. Removal of NTA was investigated in 50.5 mm i.d. by 1.17 m long soil columns under unsaturated conditions at 15°C. Septic tank effluent containing 20 mg NTA l⁻¹ was dosed to soil columns four times a day at an overall loading rate of 1 gpd ft⁻² for a 43-day period. This feed NTA concentration was routinely reduced to a steady-state concentration of 0.1 mg l⁻¹ by passage through the 1.17 m of soil, after an indigenous soil microflora became sufficiently established over a 25 day period. In addition, the results of samples taken on day 21 demonstrated that greater than 75% removal of NTA can be expected in a soil depth of less than one-third meter.     

The effects of the COD:P ratio on laboratory activated sludge systems

Laboratory activated sludge systems were operated at various COD:P ratios to study the effects of the influent phosphorus concentration on COD removal efficiency, cellular phosphorus, carbohydrate and protein contents, and alkaline phosphatase activity. In varying the COD:P ratio, the COD was held constant at 1000 mg l⁻¹ and phosphorus concentrations of 1, 2, 3, 5, 7, 9, 10, 20, 35 and 50 mg l⁻¹ were used. The optimum COD:P ratio for this study was found to be 100:1. Increasing the phosphorus concentration in the influent above one percent of the influent COD did not provide for an increase in the COD removal nor for significant changes in the cellular protein and carbohydrate content or the alkaline phosphatase activity.     

Operating characteristics of the aerated submerged fixed-film (ASFF) bioreactor

A multi-stage fixed-film reactor was developed in which a stationary submerged biofilm is attached to ceramic tiles under diffused aeration. Tracer studies revealed that the reactor's hydraulic regime is described by a CSTR-in-series model. Reactor performance at 20 °C was examined using sucrose wastewaters with organic strength up to 900 mg l⁻¹ COD, at hydraulic loadings up to 0.1 m³ m⁻²d⁻¹ and organic loadings up to 90 g CODm⁻² d⁻¹. The reactor demonstrated the capability of achieving 97% soluble COD removals at low loadings and exhibited efficient and stable performance at high hydraulic and organic loadings. Even at application rates near the rate-limiting mass loadings, there was only a 9% loss in efficiency. Reactor operation at high loadings appears to be advantageous since organic substrate removal rates and attached biomass per unit surface area increased with the increase in organic loading. This can be attributed to the good oxygen transfer and the considerable quantity and type of attached biomass attained. Staging of the reactor proved to be effective in eliminating short circuiting and damping excessive loadings, although the majority of COD removal occurs in the first stage which retains the greatest quantity of attached biomass. A good quality effluent was produced.     

High-rate overland flow

Recommended loading rates for treating raw domestic wastewater by overland flow are 6.3–15 cm wk⁻¹. Information provided in the literature yields little insight regarding the upper range of hydraulic loading rates that could be effectively treated by overland flow. Therefore, field investigations were conducted to evaluate the performance of the overland flow system at overland flow rates from 0.95 m³ day⁻¹ m⁻¹ width of slope (13 cm wk⁻¹ to 4.15 m³ day⁻¹ m⁻¹ (57 cm wk⁻¹).Preliminary treated municipal wastewater was pumped to overland flow slopes, each approx. 3.7 m wide and 36.5 m long. The slope of each plot was 2.5%. The cover crop consisted of a mixture of ryegrass, bluegrass and fescue grass. The plots were operated for 2 years at six different hydraulic loading rates.Effluent BOD₅ concentration averages varied from 6 to 11 mg l⁻¹. The reduction of influent BOD₅ concentration ranged from 87 to 93%. Mean effluent suspended solids values were from 6 to 9 mg l⁻¹ with reductions of influent concentrations of 91–95%. Hydraulic application rate had little effect on percent BOD₅ or suspended solids removal.Total phosphorus reductions were minimal at all hydraulic application rates due to limited soil water contact.Ammonia concentration in the effluent ranged from 1 mg l⁻¹ NH₃-N at the 0.95 m³ day⁻¹ m⁻¹ (13 cm wk⁻¹) applied flow rate of 11.7 mg l⁻¹ NH₃-N at the 4.15 m³ day⁻¹ m⁻¹ (57 cm wk⁻¹) loading rate. Ammonia and nitrogen reductions decreased as the applied flow rate increased. Consequently, lower overland flow rates are necessary for nitrogen removal.The use of high-rate overland flow could potentially reduce the land necessary for this form of land application, if nutrient removal was not a local concern.     

腈纶纱染色废水预处理工程的设计与运行

为使厂内处理水质达到接管标准,采用水解／塔式生物滤池和混凝沉淀工艺作为腈纶纱染色废水预处理工艺。工程运行表明,原水COD≤1600mg／L时,适当增大回流量,水解／塔式生物滤池对COD的去除率可达57％;再经混凝沉淀处理,可去除45％的COD,出水COD〈380mg／L,能满足接管要求。另外,出水色度、SS也优于接管标准。因此,采用上述工艺对腈纶纱印染废水进行预处理在技术上是可行的,经济上也是可以接受的（运行费用为1．82元／m^3）。     

The effect of polysaccharidic gums on activated carbon treatment of textile wastewater

The activated carbon treatment of wastewater originating from the Celanese Canada Ltd., Carpet plant at Sorel, Quebec, was tested in this study. Typical plant effluent was characterized and prepared. Soluble organics in the synthetic effluent varied between 75–185 mg TOC 1⁻¹, consisting of dyes (10%) process chemicals (75%) and the soluble guar gum (15%) used as a viscosity adjusting additive in the newly installed continuous dyeing process.The activated carbon adsorption of the guar gum from its pure solution was examined in laboratory tests. Improved adsorption was observed at low pH values and at elevated adsorption temperatures. Lignite-based carbon out-performed bituminous coal-based carbon. At 30 mg TOC 1⁻¹ of soluble guar gum, low carbon loading in the range of 3–8 mg TOC g^–1 was recorded for various types of carbon at 20°C and neutral pH.Activated carbon adsorption of the typical conventional prepared dyehouse wastewater resulted in non-adsorbable residues in the range of 9–18 mg TOC 1⁻¹. Presence of 50–100 mg of polysaccharidic guar gum per liter of conventional wastewater mixture had a pronounced positive effect on the adsorption process. This is reflected in an increase in both the carbon loading at initial concentration and the adsorption isotherm slope.     

Pentachlorophenol biodegradation—II : Anaerobic

The fate of pentachlorophenol (PCP) during anaerobic digestion of sewage sludge solids was tested in a three phase protocol. Phase I involved acclimation; Phase II investigated biodegradation in semicontinuous-flow, stirred-tank reactors at solids retention times of 10, 20 and 40 days; phase III assessed the importance of nonbiological removal mechanisms and collected additional data concerning the extent of biodegradation. PCP was found to inhibit methanogenesis in unacclimated cultures at concentrations in excess of 200 μg l⁻¹ and thus acclimation of the digesters to PCP required very gradual increases in the influent concentration thereby allowing enrichment of organisms capable of degrading PCP. Once acclimation was achieved, digesters receiving influent containing 5.0 mg l⁻¹ PCP achieved stable operation with effluent PCP concentrations below 5 μg l⁻¹ at all retention times studied. Sorption was shown to be unimportant in PCP removal. Volatilization was considered to be unimportant based upon results obtained in forced aeration studies. This suggested that PCP was subject to at least primary biodegradation. Other evidence collected during the study indicated that more complete biodegradation probably was occurring.     

Removal of organics from leachates by anaerobic filter

A laboratory-scale study was conducted on two anaerobic filters at several loading rates and four hydraulic detention times. Feed substrates were landfill leachates taken from a recently opened landfill (Keele Valley) and from an older site (Brock North) which had been closed for about 8 years. The strong raw leachate from the new landfill had a COD of 14,000 mg l⁻¹, a BOD/COD ratio of 0.7 and a COD/P value of 17,900. The partially stabilized leachate from the older landfill had a COD of only 3750 mg l⁻¹, a BOD/COD ratio of 0.3 and a COD/P value of 30,640.Results from the treatment of the two leachates were compared with those from a previous study of a “mature” landfill (Beare Road). It was demonstrated that the anaerobic filter could reduce the COD of leachate from landfills of different ages by 90%, at loading rates of 1.26–1.45 kg COD m⁻³ d⁻¹. Total biogas production ranged between 400 and 500 l gas kg⁻¹ COD destroyed and methane content between 75 and 85%. No phosphorus addition was required over the loading range studied.     

The use of an upflow fixed bed reactor for treatment of a primary settled domestic sewage

This study presents and demonstrates results obtained from an half full-scale upflow fixed bed reactor (UFBR) treating a primary settled domestic sewage. This study used expanded clay with an effective size of 2.7 mm containing hematite and magnetite as a granular medium.The content of TSS in the effluent treated was always between 10 and 20 mg l⁻¹ for bed depths ranging from 2 to 3 m and filtration rates of 3–6 m³m⁻²h⁻¹.The profiles taken all along the reactor show that the activity of the biomass is constant over the whole height of the reactor. Moreover, an air/water volume ratio of 2:1 is amply sufficient to satisfy the oxygen demand of the biomass. The average removal efficiency based on the soluble COD remains virtually unchanged as a function of the filtration rate at about 70% of the influent. For a final BOD₅ of 30 mg l⁻¹, loadings of 4.5–8 kg BOD₅m⁻³ can be applied. This corresponds to filtration rates of 3–6 m³m⁻²h⁻¹. The removal efficiencies for BOD₅ are then about 80%.After optimization of the backwashing conditions, the consumption of backwash water is about 5% of the volume of filtered water.Sludge measurements carried out during our experiments indicate an excess sludge production of 1 kg kg⁻¹ BOD₅ eliminated. The nature of these sludges is very similar to the biological sludges produced in the high rate activated sludge process.This study has made it possible to establish design parameters of an UFBR and to develop technology for applications. These results are applied to two wastewater treatment plants which began to operate in 1984: these plants serve population equivalents of 40,000 and 11,000.     

Aerobic treatment of concentrated wastewater in a submerged bed reactor

The performance of an aerobic submerged bed reactor applied to the treatment of a concentrated effluent was assessed. The wastewater employed was diluted stillage of alcohol distilleries, presenting a COD content of 3000–3500 mg l⁻¹. The reactor was continuously operated during 200 days, corresponding to five residence times varying from 23 to 4.5 h. The results show that 60–80% of COD removal may be obtained with 10–16 h of residence time. The advantages of this type of reactor are pointed out and suggestions of improvement are also presented.     

Anaerobic treatment of phenolic coal conversion wastewater in semicontinuous cultures

High strength wastewater (7600 mg 1⁻¹ phenolics) from the H-coal liquefaction process was diluted and fed to anaerobic, methane-producing cultures. Total phenolic concentrations of 150 and 300 mg 1⁻¹ were added to 50 ml semicontinuous cultures with hydraulic retention times of 12.5, 16.7 and 25 days. The rates of methane production and effluent concentrations of three fermentable phenolics (phenol, p-cresol and m-cresol) were monitored over a 188-day period. After acclimation to the wastewater, stable periods followed during which each of the six cultures removed essentially all of these fermentable phenolics. The duration of the stable periods decreased with increasing phenolic mass loading rates. m-Cresol was the first phenolic to appear in the effluent and its presence served as the first indicator of reduced phenolic removal capability. The effluent m-cresol concentrations from cultures receiving 300 mg 1⁻¹ total phenolics followed simple washout curves suggesting that its degradation stopped abruptly. Later, p-cresol and ultimately phenol appeared in the effluents from the cultures which received the highest phenolic mass loadings.